Note: Descriptions are shown in the official language in which they were submitted.
~ 7~ FMC 4266
This invention relates to a new process for pre-
paring organic compounds containing the cyclopropane
ring system, particularly substituted cyclopropanes having
utility as pyrethroid insecticides or as intermediates
in the preparation of pyrethroid insecticides, and to
new compositions of matter useful in the practice
of this process.
The class of pyrethroid insecticides includes both
natural and synthetic members. The active natural products
are extracted from the blossoms of pyrethrum flowers
~Chrysanthemum cinerariaefolium) grown mainly in East
Africa. The extrac~s comprise at least six closely
related vinylcyclopropanecarboxylates: pyrethrin I,
pyrethrin II, cinerin I, cinerin II~ jasmolin I and
jasmolin II. The most important natural pyrethroid,
pyrethrin I, has the structure illustrated below. The
structures of the other five components differ from
pyrethrin I in the portions of the molecule indicated
by the arrows. In cinerin II and jasmolin II the dimethyl-
~0 vinyl group at the 2-position becomes (methyl)~carbo-
methoxy)vinyl; while in the cinerins the pentadienyl
side chain in the alcohol moiety is 2-~utenyl; in
the jasmolins, 2-pentenyl.
Until recently, 1,1,1-trichloro-2,2-(bis-p-chloro-
phenyl)ethane (DDT) and 1,2,3,4,5,6-hexachlorocyclo-
hexane (BHC) were widely used as insecticides. However,
in view of the xesistance of these materials to bio-
degradation and their persistence in the environment,
new insecticides producing less environmental harm have
been sought. Pyrethroids have long been of interest
-1- ' . ~
7~
Pyrethrin I
~lCI ~
O
Structure II
~C/
Il ~0
Structure III
--2--
7~
because they are active against a wide range of
insect species, they display relatively low toxicity
toward mammals, and they do not leave harmful residues.
For example, pyrethrin I is more than 100 times as
potent toward mustard beetles (Phaedon cochleariae)
as DDT, but onl~ one-fourth to one-half as toxic
toward rats.
Altnough they possess a number of desirable chax-
acteristics, the natural pyrethroids undergo rapid
biodegradation, they have poor photooxidative stability,
their availability is uncertain, and it is costly to
extract and process them. With the discovery of the
structure of the natural pyrethroids, it has been pos-
sible to produce synthetic pyrethroids, and for a number
of years efforts have been underway around the world to
produce synthetic pyrethroid insecticides which would
overcome the disadvantages o~ the natural products. A
notable recent development was the discovery of a
dihalovinylcyclopropanecarboxylate (Structure I~) having
a toxicity toward insects more than 10,000 times greater
than that of DDT, with an oral toxicity toward mammals
similar to pyrethrin I [Elliott et al., Nature, 244,
456 (1973)]. Although Structure II, in which the alcohol
moiety is 5-benzyl-3-furylmethyl, does not have exceptional
photooxidative stability, Elliott et al. discovered that
3-phenoxybenzyl analogs (Structure III where X i5 halogen)
were remarkably resistant to photooxidative degradation
~Nature, 246, 169 (1973), Belgian Patents 800,006 and
818,811].
This application presents processes for the synthesis
~2~7'~
of pyrethroids in which the cyclopropanecarboxylic acid
part contains a dihalovinyl group in the 2-position and
describes novel compositions of matter useful in the
practice of these processes. Accordingly, processes of
this invention lead to esters of such acids which either
are or may be converted readily into pyrethroid insecti-
cides. The major advantage of this invention is to pro-
vide a convenient synthetic route to pyrethroids of the
type represented by Structures II and III.
Prior to the present invention, the known methods for
varying the nature of the substituents occupying the 2-posi-
tion in the cyclopropane ring included the ollowing:
(1) Chrysanthemic acid or a naturally occurring
chrysanthemate may be subjected to ozonolysis to produce
caronaldehyde ~Farkas et al., Coll. Czech. Chem. Com., 24,
2230 (1959)]. The aldehyde may then be treated with a
phosphonium or sulfonium ylide in the presence of a strong
base, followed by hydrolysis [Crombie et al., J. Chem. Soc.
(c), 107~ (1970); Brit. Patent 1,285,350]. Such a
reaction sequence is shown below.
COOH
V Me~S H+ ~ X
/\
-4-
~Z~'7~i
O COOM
X
Base ~ COOH
HydrQlvsis >, / \~
X )~
P \X
The reaction may be utilized where X is an alkyl group
and also where X is halogen ~South African Patent 733,528;
J. Am. Chem. Soc., 84, 854, 1312, 1745 (1962)]. The
reaction has been employed to prepare ethyl 2~ -di-
chlorovinyl)-3,3-dimethylcyclopropane-l-carboxylate, a
precursor of Structures II and III. Whereas the ylide
reaction proceeds in about 80% yield, the yield of
aldehyde from the oxidation is typically only about 20%.
The oxidative degradation originated as a tool for proof
of structure and was never intended for large-scale
preparative use. The oxidation alone requires many hours
to complete because mild conditions must be used to
minimize the possibility of a violent oxidation of the
organic compound. An overall yleld of 16% may be accept-
able when the process is used in research, but it is
much too low to be of practical commercial utility. In
addition, the starting material is costly since it is
derived from an expensive natural product.
(2) The original Staudinger synthesis of chrysanthemic
acid involved the reaction of ethyl diazoacetate with
7~76
2,5-dimethylhexa-2,4-diene followPd by saponification of
the ester lHelv. Chim. Acta, 7, 390 (1924)]. Carbene
addition to an unsaturated carbon-carbon linkag~ has
become a general reaction for the preparation of the
cyclopropane ring system ~Mills et al., J. Chem. Soc.,
133 (1973), U. S. Patents 2,727,900 and 3,808,260].
Such a reaction, illustrated below, has been employed
in the preparation of pyrethroids and also ethyl 2~
dichlorovinyl)-3,3-dimethylcyclopropane-1-carboxylate,
precursor of II and III [Farkas et al., Coll~ Czech.
Chem. Comm., 24, 2230 (1959)]. In preparing the
latter, the starting material may be the mixture of pen-
tenols obtained by the condensation of chloral with iso-
butylene.
OH
~ Ac2O Mixture of
CCl ~ Acetates
3 ~
IOH ~/
/V\_ l
CCl3
_~
Mixture of Zn HOAc CCl2
Acetates ' ~- ~/
Lc~\
'7~ii
p-Toluene- /
~ sulfonic acid~
CCl2
~ N 2 CHCOOEt ~ ~ COOEt
CC12
The conversion of the mixture of pentenols to l,l-dichloro-
4-methyl-1,3-pentadiene is reportedly only about 50%.
This, coupled with the fact that in the last step the
production of the diazo ester and its handling are
extremely dangerous on a large scale, seriously limits
the utility ~f the process. Furthermore, it is estimated
that, should the pyrethroid of Structure III become a
major agricultural commodity, commercial production by
this method of enough of the dihalovinylcyclopropane-
carboxylate to satisfy the potential demand might exhaustthe world supply of zinc.
(3) Julia has described a third general method
capable of allowing the substituents in the 2-position
of the cyclopropane ring to be varied [U. S. Patents
3,077,496, 3,354,196 and 3,652,652; Bull. Soc. Chim.
Fr., 1476, 1487 (1964)]. According to this method,
illustrated below, an appropriately substituted lactone
is first treated with a halogenating agent, opening
the ring, followed by base-induced dehydrohalogenation,
forming a cyclopropane.
'7~i
SOCl2
_____ ~Cl COOEt
EtOH ~ ~ Cl
X X
COOEt
~ Base~ ~ C~OEt
~ X
Even in ths relatively uncomplicated case where the
terminal substituents on the vinyl group are methyl and
the product is ethyl chrysanthemate, the yield is only
40%. Moreover, lactones of special interest, such as
3~ dichlorovinyl) 4-methyl-~-valerolactone are not
readily available. Even 3-isobutenyl-4-methyl-~-valero-
lactone, from which ethyl chrysanthemate is made,
requires a 3-step synthesis from 2-methylhex-2-en-5-one,
including a Grignard reaction. Grignard reactions are
difficult to carry out on a large scale and, in any
case, could probably not be utilized without destroying
a dihalovinyl group were it present.
In summary, the processes taught in the prior art
for varying the nature of the substituents occupying
the 2-position in the cyclopropane ring, particularly
processes for introducing a 2-dihalovinyl group, suffer
from a number of disadvantages, the most serious of which
are:
~2~'76
(1) The yields of cyclopropanecarboxylates are
too low for practical appli~ati~n in commerce;
(2) The starting materials are not readily available,
requiring additional synthetic steps, adding ~o costs
and increasing the price of the product beyond that
which the market ~ill bear;
(3) The processes all involve at least one reaction
which is difficult and dangerous to carry out on a large
scale, inviting the risk of fire or explosion.
I~ has now been found that the serious disadvantages
inherent in the processes of the prior art can be largely
overcome by novel syntheses, which proceed in high yield,
using readily available, comparatively inexpensive
starting materials, in a few safe, commercially feasible
st~ps, by way of novel compositions of matter as inter-
mediates/ to produce pyrethroids of the type represented
by Structures II and III or intermediates converted
readily into such pyrethroids. The synthetic steps
employed in the processes of this invention proceed
in high yield; yields of 90% cr higher are common. In
addition, dihalovinylcyclopropanecarboxylates in which
the more active trans isomer ranges in amount from
50% to 90% can be made with almost no variation in yield.
The novel processes of this invention are illus-
trated specifically by the following chemical equations
and Examples wherein, starting with readily available
3-methyl-2-buten-1-ol and ethyl orthoacetate, either
the potent, persistent pyrethroid, III, or ethyl 2-(~,~-di-
chlorovinyl)-3,3-dimethylcyclopropanecarboxylate, an
intermediate in the preparation of III, is produced.
~2~L~7'76
ethyl 3-phenoxy-
~acetate ~= alcohol ~
Y
~'- OH ~ - COOEt ~ ~ COO
~CooX:Elt3 ~/~ --XL~El2
or or
_ base CCl
~13 ~ x~2
7 , 0~
_ III
In the Examples which follow, and elsewhere in this
application, temperatures are in degrees centigrade, and
percentages are by weight. For each boiling point (b.p.)
taken at reduced pressure, the pressure is given in
millimeters of mercury, for example, b.p. 116/0.18 mm
means a boiling point of 116C at 0.18 mm of mercury.
Where ir spectra are given, only the frequencies of the
most prominent absorption maxima appear. For the nmr
spectra tetramethylsilane was employed as an internal
standard, and in the nmr data the abbreviations have
the following significance: s, singlet; d, doublet;
t, triplet; q, quartet; m, multiplet. Any of these
abbreviations may be preceded by b for broad or d
for double, for example, d.d., double doublet;
b.t., broad triplet.
--10--
~l2~ 7~i
_ample 1
Synthesis of 3-Phenoxybenzyl 2-(~-Dichlorovinyl)-
3,3-dimethylcyclopropanecarboxvla~e
A. Preparation of ethYl 3,3-dimethvl-4-pen~enoate
A mixture of 0.65 g of 3-methyl-2-buten-1-ol,
2.43 g of ethyl orthoacetate and 50 mg of pehnol was
heated at 120 with stirring. After 2 hours, the temp-
erature wa~ increased to 140 where it was maintained
for 20 hours. When ethanol evolution had ceased, the
mixture was dissolved in benzene to a total volume of
5 ml. Gas chromatographic analysis of the benzene
solution showed that ethyl 3,3-dimethyl-4-pentenoate had
been produced in 9Z% yield (ses Example V for physical
properties).
B. Transesterification between 3-phenoxybenzyl
alcohGl and ethYl 3,3-dimethyl-4-pentenoate
A mixture of 374 mg of ethyl 3,3-dimethyl-4-pen-
tenoate, 400 mg of 3-phenoxybenzyl alcohol and 16 mg of
sodium ethoxide in 10 ml of toluene was heated under
reflux for 24 hours, with a Dean-Stark apparatus con-
taining a molecular sieve to absorb the evolved ethanol.
The mixture was neutralized by adding an anhydrous ether
solution of hydrogen chloride. The neutral solution
was poured into water. The ether layer was separated,
dried over magnesium sulfate, and distilled to give
520 mg (70~ yield) of 3-phenoxybenzyl 3,3-dimethyl-4-pen-
tenoate, b.p. 155-158/0.3 mm.
Analysis:
Calculated for C20H22O3: C, 77.39; H, 7.14;
Found: C, 77.14; H, 7.11.
--11--
76
nmr ~ ppm (CCl4): 7.32-7.08 (m, 4H3, 7.05-6.70
(m, 5H), 5.76 (d.d., lH), 4.92 (s, 2H), 4.96-4.70
(m, 2H), 2.22 (s, 2H), 1.08 (s, 6H).
C. Addition of carbon tetrachloride to 3-phenoxY-
benzYl 3,3-dimethYl-4-Pentenoate
A mixture of 245 mg of 3-phenoxybenzyl 3,3-dimethyl-
4-pentenoate in 5 ml of carbon tetrachloride was charged
to a pressure vessel, and to it was added 2 mg of benzoyl
peroxide. The vessel was purged with argon and sealed.
The sealed vessel was heated for 5 hours at 140, then
cooled, and an additional 2 mg of benzoyl peroxide was
added. The vessel again was purged, sealed and heated
at 140 for S hours. The procedure was repeated twice
more after which the vessel was cooled, and the contents
were washed successively with water, saturated aqueous
sodium bicarbonate and water. The washed mixture was
dried over magnesium sulfate, and the solvent was removed
under reduced pressuxeO The residue was purified by silica
gel chromatography with benzene as the eluting solvent to
give 300 mg (82% yield) of 3-phenoxybenzyl 4,6,6,6-tetra-
chloro-3,3-dimethylhexanoate.
Analysis:
Calculated for C2lH22Cl4O3: C, 54.33; H, 4.78; Cl, 30.55;
Found: C, 54.76; H, 4.88; Cl~ 30.24.
nmr ~ ppm (CCl4): 7.35-7.05 (m, 4H), 7.05-6.75
(m, 5H), 4.96 (s, 2H), 4.30 (d.d., lH), 3.30-2.80
~m, 2H), 2.57 (d, lH), 2.26 (d, lH), 1.15 (s, 3H),
1.07 (s, 3H).
~. Simultaneous cyclization and dehvdrochlorination
A solution of 200 mg of 3-phenoxybenzyl 4,6,6,6-
-12-
~l2~ 7~
tetrachloro-3,3-dimethylhexanoate in 1 ml of anhydrous
tetrahydrofuran was added dropwise to a suspension of
124 mg of sodium t-butoxide in 5 ml of anhydrous tetxa-
hydrofuran during which the reaction mixture was cooled
in ice. ~fter 1 hour, the mixture was allowed to warm to
room temperature and then it was heated under reflux for
1 hour. The mixture was neutralized by the addition of an
anhydrous ether solution of hydrogen chloride. The neu-
tralized mixture was poured into ice water and extracted
with diethyl ether. The ether extract was dried over mag-
nesium sulfate, and the solvent was removed under reduced
pressure. The residue was purified by column chromato-
graphy on a silica gel column with benzene as the eluting
solvent to give 126 mg (75~ yield) of 3-phenoxybenzyl
2-(B,B-dichlorovinyl)-3,3-dimethylcyclopropanecarboxylate.
Analysis:
nmr ~ ppm (CCl4): 6.80-6.50 (m, 9H), 6~25 (b.d., 0.5H),
5.60 (d, 0.5H), 5.05 (s, 2H), 2.40-1.40 (m, 2H),
1.40-1.05 (m, 6H).
ExamPle II
Synthesis of Ethyl 2-(B~B-Di-chlorovinyl)
3,3-dlmethylcycloProPanecarboxYlate
A. Additi_n of carbon tetrachloride to ethyl
3,3-dimethyl-4-pentenoate
To a solution of 135.2 mg (0.5 mmole) of ferric chlor-
ide hexahydrate and 146.3 mg (2.0 mmoles) of n-butylamine
in 2.19 g of dimethylformamide contained in a pressure
vessel was added 1.56 g (10 mmoles) of ethyl 3,3-dimethyl-
4-pentenoate and 4.26 g (30 mmoles) of carbon tetrachloride.
The vessel was sealed and heated for 15 hours at 100.
~Z:~77~
The vessel was then cooled, and the contents were dis-
solved in diethyl ether. The ethereal solution was
washed successively with lN hydrochloric acid, saturated
aqueous sodium bicarbonate and saturated aqueous sodium
chloride. The washed solution was dried over magnesium
sulfate and distilled to give 2.79 g (90% yield) of
ethyl 4,6,6,6-tetrachloro-3,3~dimethylhexanoate,
b.p. 116/0.18 mm.
Analysis:
Calculated for CloHl6Cl4O2: C, 38.74i H, 5.20; Cl, 45.74;
Found: C, 38.91; H, 5.07; Cl, 45.85.
nmr ~ ppm (CCl4): 4.37 (d.d., lH), 4.07 (cl, 2H),
3.40-2.85 (m, 2H), 2.40 (q, 2H), 1.27 (t, 3H),
1.20 (d, 6H).
B. Simultaneous cyclization and dehydrochlorination
Into a solution of 3.1 g (10 mmoles) of ethyl
4,6,6,6-tetrachloro-3,3-dimeth~lhexanoate in 40 ml of
absolute ethanol was added dropwise 20 ml of an ethanol
solution containing 1.5 g (22 mmoles) of sodium ethoxide.
The mixture was stirred at room temperature for 1 hour
after the addition was completed, then refluxed fox
1 hour. The mixture was reduced by distillation to
about one-tenth its original volume and cooled with ice,
and the residue was neutralized by the addition of lN
hydrochloric acid. The neutral solution was extracted
with diethyl ether, and the ether extract was washed
successively with saturated aqueous sodium bicarbonate
and saturated aqueous sodium chloride. After drying
over magnesium sulfate, the solution was distilled to
give 2.12 g (89% yield) of ethyl 2-(~,~-dichlorovinyl)-
-14-
~2~
3,3-dimethylcyclopropanecarboxylate, b.p. 77/0.3 mm
(see Example III for physical properties).
The no~el processes just described specifically are
capable of general application as represented by the fol-
lowing chemical equations:
Step l _ _
~ OH >7 3 R~
R3 R R3ORIRt
_ ~W _ ~
R2 R4
R5l A
R6 R7
Step 1' 2 R4
A + R8OH ~ ~ 5
R COOR 8
R6 R7
A'
Step 2
. X CX3
A or A' + CX4 ~ R ~ COOR
-15-
7~
Step 3 R3 R7
X
B + base __~ R ~ X ~ CX2
R R7~ COOR
L ~CX3 ~ C
Z
In the definitions of the substituent R groups
the term "lower", modifying such expressions as alkyl,
alkene, alkoxy, and so forth, means 1 to 6 carbon atoms,
preferably 1 to 4 carbon atoms. X is a halogen atom.
The radicals -COORl and -COORa are carboxylate functions;
ORl and ORB are alcohol residues in which Rl is a lower
alkyl group and Ra is represented by the formula:
CH
R9
wherein,
R9 is a hydrogen atom or a cyano group;
Rl~ is a hydrogen atom, a lower alkyl group, a
phenoxy group, a benzyl group or a phenylthio group;
Rll is a hydrogen atom or a lower alkyl group; and
Rl 2 is a divalent oxygen or sulfur atom or a vinylene
-16-
76
group, -CH=CH-.
R is either Rl or RB.
Except as otherwise specified in the detailed des-
criptions for each step, the radicals R2 to R7 appearing
in the equations may be the following:
Each of R2 to R7 is hydrogen, lower alkyl, lower
alkenyl, lower alkynyl, lower cycloalkyl, phenyl,
aralkyl such as benzyl, lower alkoxycarbonyl, lower
alkanoyl, aroyl such as benzoyl, di(lower alkyl)amide~
nitrile, or lower haloalkyl, and each pair of R2 with R3,
R4 with Rs, and R6 with R7 may constitute a lower
alkylene chain of at least 2 carbon atoms.
In the process of Step 1 an alkenol is reacted with
an orthoester to produce a y-unsaturated carboxylate,
Structure A. It has been found that the mixed orthoester,
Structure W, is an intermediate and may be isolated.
Other reactants capable of producing this intermediate,
useful in the practice of the process, could be employed
to produce A; for example, an alkenol may be reacted
with an appropriate ketene acetal to produce such a
mixed orthoester from which the y-unsaturated arboxylate,
A, may be derived. The product of Step 1 is a lower
alkyl ester which may optionally be reacted in Step 1'
by ester interchange with an alcohol, ~BOH, chosen from
among alcohols which commonly appear in pyrethroids;
for example, 3-phenoxybenzyl alcohol. The ester so
produced, Structure A', can be carried through the pro-
cesses of Steps 2 an~ 3 to yield, as the product of
Step 3, a dihalovinylcyclopropanecarboxylate which is a
pyrethroid insecticide.
~2~,t~7~;
In the process of Step 2 the r-unsaturated carboxy-
late, A or A ~ is then treated with a carbon tetrahalide
to produce a y-halocarboxylate of Structure B The
~-halocarboxylate may be dehydrohalogenated subsequently
with a base to produce any one of four different products,
depending upon the choice of reaction conditions. The
novel intermediates represented by Structures X, Y and Z,
each representing the elimination of 1 mole of HX fro~
the ~-halocarboxylate, B, may, but need not, be isolated.
Each of the intermediates, X, ~ and Z, is a useful
composition of matter which can be carried to the dihalo-
vinylcyclopropanecarboxylate, Structure C, by the elimina-
tion of additional HX. If the optional ester interchange
of Step 1' was not carried out on the y-unsaturated
carboxylate, A, ~he Rl group of the dihalovinylcyclo-
propanecarboxylate, C, may be converted by known pro-
cesses to RB to produce an active insecticide.
A wide variety of cyclopropanecarboxylates closely re-
lated to the dihalovinylcyclopropanecarboxylates may be pre-
pared by the processes of this invention. For example, inStep 2 in place of carbon tetrahalide other structurally simi-
lar polyhalogenated compounds, including chloroform, bromoform,
a,a,a-trihalotoluene, lower trihaloacetates, trihaloacetoni-
triles, and polyhalogenated lower alkanes, may be added to the
olefinic dcuble bond. Such additions will give products analo-
gous to the ~-haloalkanoates described above, but with a sub-
stituent other than halogen in the ~-position, a substituent
such as hydrogen, lower alkyl, lower haloalkyl, phenyl, nitrile,
or lower alkoxycarbonyl. These products will undergo dehydro-
halogenation and ring closure to form cyclopropanecarboxy-
-18-
~L2~7~6
lates useful as insecticides or in the preparation of
insecticides. Similarly, intermediates of types X and Y
may be prepared with the above-noted substituents other
than halogen in the ~-position, and these compounds may
also be used to prepare ~-substituted vinylcyclopropane-
carboxylates where a ~-substituent is-other than halogen.
For example, ethyl 4,6-dichloro-3,3-dimethyl-5-hexenoate is
reacted with sodium t-butoxide in benzene to form
ethyl 2-.~-chlorovinyl)-3,3-dimethylcyclopropanecarboxylate.
Other means of introducing halogen may also be used .
to prepare compounds capable of undergoing the dehydro- ~!
halogenation and ring closure of Step 3. ~-Unsaturated ~1
alkenoates may be halogenated in the ~-position with a
halogenating agent, for ~xample N-bromosuccinimide (NBS),
to form compounds analogous to the X intermediates des~
cribed above. Such compounds will also undergo dehydro-
halogenation and ring closure to form cyclopropane carboxy-
lates. The reaction sequence is illustrated below:
COORl R2 COORl R2 COOR
--1~
~2~776
wherein
a) Rl is lower alkyl;
b) R2 and R3 each is hydrogen, lower alkyl, lower
cycloalkyl, phenyl, or aralkyl such as benzyl;
R2 and R3 together may constitute a lower alkylene
chain of at least 2 carbon atoms; and when one
of R2 and R3 is other than hydrogen, the other
may be lower alkoxycarbonyl, lower alkanoyl,
aroyl such as benzoyl, di~lower alkyl)amide,
or nitrile;
c) R7 is hydrogen, lower alkyl, lower cycloalkyl,
phenyl, aralkyl such as benzyl, lower alkoxy-
carbonyl, lower alkanoyl, aroyl such as benzoyl,
di(lower alkyl)amide, or nitrile.
d) Rl 3 and R1 4 each is hydrogen, lower alkyl, or
phenyl; and
e) X is halogen.
Step 1
The first process of this invention is represented
by Step 1 in which an alkenol is reacted with an ortho-
-l9(a)-
lZ~7~
ester to produce a y-unsaturated carboxylate, A, by way
of the mixed orthoester, W, an intermediate which may or
may not be isolated. Examples of alkenols which may be em-
ployed in the process of Step 1 are allyl alcohol, crotyl
alcohol, 4-methyl-1-phenyl-3-penten-2-ol, 4-methyl-3-
penten-2-ol, cinnamyl alcohol, 3-methyl-2rbuten-1-ol,
2,4-dimethyl-3-penten-2-ol, 5-methyl-4-hexen-3-ol,
2-methyl-2-hepten-4-ol, 1-cyclopentyl-3-methyl-2-buten-
l-ol and the like. The specific alkenol to be employed
in Step 1 will depend upon the desired nature of R2, R3,
R4, and R5. These alkenols are readily available or are
derived easily from commercial raw materials. In order
to produce a 2-dihalovinylcyclopropanecarboxylate such
as II or III, having dimethyl substitution in position 3
of the cyclopropane ring, 3-methyl-2-buten-1-ol is pre-
ferably employed. 3-Methyl-2-buten-1-ol is available as
a by-product from the manufacture of isoprene.
Examples of orthoesters which may be employed in
the process of Step 1 include, in the acid part, alkanoic
acids such as acetic acid, propionic acid, butyric acid,
isobutyric acid and valeric acid; and in the alcohol
part, lower alkanols such as methanol and ethanol; for
example, ethyl oxthopropionate, methyl orthoacetate,
ethyl orthoacetate, and the like. The acid and alcohol
parts of the orthoester will be chosen to yield the de-
sired Rl, R6, and R7 groups in the y-unsaturated carboxylate.
~he orthoesters may be prepared readily by the alcoholysis
of the corresponding nitriles. In producing a y-unsatur-
ated carboxylate which is to be carried through the re-
maining processes of this invention to yield a dihalo-
-20-
~l2~7~
vinylcyclopropanecarboxylate, ethyl orthoacetate is
preferably employed.
~ lthough the reaction between the al~enol and the
orthoester does not require it, an acid catalyst in-
creases the rate of the reaction. Examples of acid cata-
lysts which may be employed include phenols such as
phenol, ortho-, meta- or para-nitrophenol, ortho-,
meta- or para-cresol, ortho-, meta- or para-xylenol,
2,6-dimethylphenol, 2,6-di-t-butylphenol, 2,4,6-tri-
sec-butylpheno~, 2,4,6-tri~t-~utylphenol, 4-methyl-2,6-
di-t-butylphenol, 4-methyl-3,5-di-t-butylphenol, hydro-
quinone, 2,5-di-t-butylhydroquinone, ~ or ~-naphthol
and the like; lower aliphatic acids such as acetic acid,
propionic acid, butyric acid, isobutyric acid, cyclo-
hexanecarboxylic acid, valeric acid and the like; aromatic
carboxylic acids such as benzoic acid, meta-chloro-
benzoic acid and the like; sulfonic acids such as benzene-
sulfonic acid, para-toluenesulfonic acid and the like;
incrganic acids such as hydrochloric acid, sulfuric
acid, phosphoric acid, boric acid and the like; and
Lewis acids such as zinc chloride, ferric chloride,
mercuric acetate and the like. In order to avoid side
reactions such as dehydration of the alkenol, the catalysts
generally used are phenols, aliphatic acids having 2 to 6
carbon atoms, and aromatic acids. Phenol is conv~nient
and effective.
The process of Step 1 does not require a solvent,
but solvents which do not adversely affect the reaction
or the product may be employed. Useful solvents include
decalin, n-octane, toluene, ortho-, meta- or para-xylene,
-21-
- ~2~ '7~;
di-n-butyl ether, N,N-dimethylformamide and the like.
Although the s~oichiometry suggests that the alkenol
and the orthoester should be present in eguimolar amounts,
it is advantageous to use an excess of the orthoester,
for example 20 to 100~ excess or more. The acid catalyst
can be used in an amount ranging from about 0.001 to 20
by weight, preferably from 1 to 15% by weight, based
on the amount of alkenol reacted.
The process of Step 1 can be conducted at tempera-
tures ranging from about 20 to 250C, and an effective
procedure is to conduct the reaction in two stages, the
first stage at a temperature ranging between 20 and
120C and the second stage at a temperature between
100 and 250C, If ethyl orthoacetate is employed as a
reactant, and the reaction is conducted at atmospheric
pressure, the first stage is usually conducted at a
temperature between about 100 and 120C, removing
ethanol by distillation as it is produced; the second
stage is usually conducted at a temperature between
about 140 and 170C.
Step 1'
The y-unsaturated carboxylate, A, may, if desired,
be reacted according to the process of Step 1' in which
the alcohol residue, oR8, is interchanged for the lower
alkanol residue, ORl, to produce the y-unsaturated
carboxylate, A', OR~ being chosen from among alcohol
residues which commonly appear in pyrethroids. The
y-unsaturated carboxylate, A', when carried through
the processes of this invention represented by Steps 2
and 3, may lead directly to a dihalovinylcyclopropane-
~2~77~
carboxylate, C, which is a pyrethroid insecticide;for example, Structure III.
For the purposes of the process of Step 1':
R2 and R3 each is hydrogen, lower alkyl, lower
alkenyl, lower alkynyl, lower cycloalkyl, phenyl, or
aralkyl such as benzyl; R2 and R3 together may constl-
tute a lower alkylene chain of at least 2 carhon atoms;
and when one of R2 and R3 is other than hydrogen, the other
may be lower alkoxycarbonyl, lower alkaroyl, aroyl such as
benzoyl, di(lower alkyl)amide, or nitrile.
R~, R5, R6 and R7 each is hydrogen, lowar alkyl,
lower alkenyl, lower alkynyl, lower cycloalkyl, phenyl,
or aralkyl such as benzyl; each pair of R4 with Rs and
R6 with R7 may constitute a lower alkylene chain of at
least 2 carbon atoms.
The y-unsaturated carboxylate and the alcohoi may
be employed in equimolar amounts, but generally one
reactant is in excess. ~he ethyl ester is convenient
to use, particularly with sodium ethoxide as a catalyst.
During the reaction ethanol is removed from the mixture
as it is formed. A solvent such as toluene may be
employed.
Instead of introducing R~ in the manner just des-
cribed, the interchange may be conducted at another point
in the process, and other synthetic methods can be used
for converting an Rl ester to an R8 ester such as
hydrolysis followed by esterification, for example,
reaction of a dihalovinylcyclopropanecarboxylic acid
chloride with an alcohol R8OH in the presence of
a base.
~;2P~7~736
Step 2
Th~ process of this invention represented by
Step 2 is a reaction between a y-unsa~urated carboxylate,
A or A', and a carbon tetrahalide, CX4, in the presence
of a catalyst to produce a ~-halocarboxylate, B. The
~-unsaturated carboxylate, A or A', may be prepared as
described above.
For the purposes of the process of Step 2:
R2, R3, R6 and R7 each is hydrogen, lower alkyl,
lower cycloalkyl, phenyl, aralkyl such as benzyl, lower
alkoxycarbonyl, lower alkanoyl, aroyl such as benzoyl,
di(lowar alkyl)amide, nitrile, or lower haloalkyl; each
pair of R2 with R3 and R6 with R7 may constitute a lower
alkylene chain of at least 2 carbon atoms.
R4 and Rs are hydrogen.
Carbon tetrahalides which may be employed in this
process include carbon tetrachloride, carbon tetra-
bromide, bromotrichloromethane, bromochlorodifluoro-
methane and iodotrichloromethane. In general, the carbon
tetrahalide will contain no more than two fluorine atoms,
and no more than one iodine atom. When it is desired
to produce a dichlorovinylcyclopropanecarboxylate by the
processes of this invention, carbon tetrachloride, bromo-
trichloromethane or dibromodichloromethane may be employed;
although bromotrichloromethane reacts smoothly, carbon
tetrachloride is more readily available and less
expensive.
The process of ~tep 2 requires a catalyst, and two
distinct types of catalyst systems have been found to
be useful: (1) free radical initiators or (2) transition
-24-
~2~76
metal salts and coordination complexes between transition
metal salts and various electron donors such as organic
amines, carbon monoxide, acetylacetone, and the like.
The reaction can also be catalyzed by radiation; for
example, ultraviolet light, a variant of the reaction
employing a free radical catalyst. In order for the
reaction to be effectively catalyzed by ~isible light,
the carbon tetrahalide should preferably contain at
least one bromine or iodine atom.
Examples of free radical catalysts which may be
used include azobisisobutyronitrile (AIBN), benzoyl
peroxide (BPO), acetyl peroxide, di-t-butyl peroxide,
t-butyl peracetate, t-butyl perbenzoate, t-butyl per-
phthalate, t-butyl hydroperoxide and the like. The use
of a catalytic amount of a free radical catalyst is
generally sufficient, but arnounts as high as 20% based
on the number of moles of ~-unsaturated carboxylate may
be employed, especially if the catalyst is added in in-
crements.
Examples of transition metal salts which can be
used are cuprous or cupric chloride, ferrous or ferric
chloridel cobalt, nickel, zinc, palladium, rhodiwn or
ruthenium chloride, copper cyanide, copper thiocyanide,
copper oxide, copper sulfide, copper or iron acetate,
iron citrate, iron sulfate, iron oxide, copper or iron
acetylacetonate and the like, including hydrates of
the salts listed.
Examples of organic amines which can be used in
conjunction with the transition metal salts are aliphatic
amines such as n-butylamine, diisopropylamine, triethyl-
-25-
7 E;
amine, cyclohexylamine, benzylamine, ethylenediamine,
ethanolamine and the like, aromatic amines such as
aniline, toluidine and the li~e; heterocyclic amines such
as pyridine and the like; as well as amine salts such as
diethylamine hydrochloride and the like. With a view to
the availability of materials and optimum yield, a
combination of a transition metal halide and an aliphatic
amine is preferred, especially ferric chloride hexahydrate
and n-butylamine. For maximum yield of the des:ired pro-
duct it has been found effective to employ more thanabout 1.5 moles, preferably between about 2 and 10 moles,
of organic amine per mole of transition metal salt. In
yeneral, the transiticn metal catalyst may be used in
catalytic amounts, about 0.01% based on the nu~er of
moles of ~-unsaturated carboxylate, but higher concen-
trations increase the reaction rate, and 10% or more may
be used to advantage.
When a free radical catalyst is employed, approxi-
mately equimolar amounts of the starting materials are
used. Generally the reaction is carried out in the absence
of a solvent, but solvents which do not adversely affect
the reaction, for example, carbon disulfide or hydrocarbon
solvents such as benzene or toluene, may be used. The
rea~tion may also be conducted in the presence of an
excess amount of the carbon tetrahalide as a solvent;
the excess can be recovered and recycled. The reaction
is generally conducted at a molar ratio of carbon tetra-
halide to ~-unsaturated carboxylate between about 1:1
and 4:1.
When catalyzed by light, the reaction is conducted
-26-
;776
at temperatures between about 25 and 100C. When free
radical catalysts are used, the reaction is generally
conducted at a temperature between about 50 and 15QC.
When a transition metal salt or a coordination com-
plex is used as the catalyst, the reactants may be in ap-
proximately equimolar amounts, but the carbon tetrahalide
may also be employed in excess. A solvent is not necessarily
required in the reaction, but solvents which do not adversely
affect the reaction or the product may be employed if de-
sired; for example acetonitrile, dimethylformamide, alcohols,aliphatic hydrocarbons, aromatic hydrocarbons, and the like,
may b~ used. ~lternatively, the carbon tetrahalide may be
used as the solvent as well as a reactant, if the carbon
tetrahalide is a liquid. When a solvent other than excess
carbon tetrahalide is used, a polar solvent is preferred,
since the yield generally is increased thereby. A coordination
complex of a metal salt with an electron donor is usually
preferred to the salt itself, butylamine being a useful
donor and ~erric chloride hexahydrate a useful salt. When
a metal salt or coordination complex is employed as the
catalyst, the reaction is generally conducted in the
temperature range 50 to 200C, preferably between
about 70 and 150C.
The coordination complex catalysts offer advantages over
most free radical catalysts in that they retain their activity
ovex a long period of time and, in addition, can be reused.
Step 3
The process of this invention represented by Step 3
involves the base-induced dehydrohalogenation of the y-halo-
carboxylate, B, to produce a dihalovinylcyclopropanecar-
-27-
~æ~7~7s
boxylate, C, by way of the intermediates X, Y or Z, compo-
sitions of matter which are useful in the practice of the
process, which may or may not be isolated depending upon the
reaction conditions. In the conversion of B to C, 2 moles
of acid, HX, are eliminated and the elimination can be made
to take place one mole at a time.
The structure of the ~-halocarboxylate, B, will be
dictated by the structures of the materials emp~oyed in
Steps 1, 1' and 2.
For the purposes of the process of Step 3:
R2 and R3 each is hydrogen, lower alkyl, lower alkenyl,
lower alkynyl, lower cycloalkyl, phenyl, or aralkyl such as
ben~yl, R2 and R3 taken together may constitute a lower alky-
lene chain of at least 2 carbon atoms; and when one of R2 and
R3 iS other than hydrogen, the other may be lower alkoxy-
carbonylO lower alkanoyl, aroyl such as benzoyl, di(lower
alkyl)amide, or nitrile.
R4, Rs and Rs are hydrogen.
R7 is hydrogen, lower alkyl, lower alkenyl, lower
alkynyl, lower cycloalkyl, phenyl, aralkyl such as benzyl,
lower alkoxycarbonyl, lower alkanoyl, aroyl such as benzoyl,
di(lower alkyl)amide or nitrile.
When it is desired to produce a dihalovinylcyclopro-
panecarboxylate which may be converted readily into pyreth-
roid insecticides of the type represented by II and III, the
~-halocarboxylate will be chosen such that R4, R5, R6 and R7
are hydrogen; R2 and R3 are methyl groups and X is chlorine.
Among compounds of that type the novel compound ethyl 3,3-di-
methyl-4,6,6,6-tetrachlorohexanoate has been found especially
useful.
-28-
` ~2~7176
The nature and quantity of the base which is used, the
solvents, and the temperature determine whether the product
of the reaction will be one of the intermediates X, Y or Z,
or whether the reaction will proceed all the way to the
dihalovinylcyclopropanecarboxylate, C.
To produce the dihalovinylcyclopropanecarboxylate, C,
directly in the process of Step 3, B is reacted with anhydrous
base including, for example, sodium hydroxide and potassium
hydroxide, provided that the solvent is anhydrous; alkali
metal alkoxides such as sodium ethoxide, sodium methoxide,
sodium t-butoxide, potassium t-butoxide, and the like, pre-
viously prepared or prepared in place; sodium hydride; sodium
naphthalene and the like. Sodium hydride or an alkali metal
alkoxide is particularly use~ul. At least 1.5 molar equi-
valents of the base, for example 2 to 5 molar equivalents per
mole of y-halocarboxylate are used. The process is carried
out advantageously in a solvent such as methanol, ethanol,
t-butanol, and the like, as well as ethers such as diethyl
ether, tetrahydrofuran, dimethoxyethane and the like.
It was found that the ratio of cis to trans isomers in
the final product can be varied over an unexpected range by
simply changing the temperature employed. For example, when
the base-solvent combination is sodium t-butoxide in tetra-
hydrofuran, and the reaction is conducted at about 0, the
cis:trans ratio is about 50:50; whereas when the reaction
is carried out near room temperature from intermediate Y,
the cis:trans ratio is approximately 10:90.
To produce directly the dihalovinylcyclopropane-
carboxylate, C, from B, the reaction may be conducted in the
temperature range 50 to 200C, but preferably 60 to 100C;
-29-
but if sodium or potassium t-butoxide is used with an
ethereal solvent such as tetrahydrofuran the reaction may
be carried out as low as -30C.
To conduct the process of Step 3 so as to stop at inter-
mediate X, the reaction is conducted at a temperature no
higher than about 25C in order to avoid the fo~mation of Y,
which is produced by way of X, and the y-halogen atom in B
usually has a high atomic number, such as bromine or iodine.
In general, the use of an aprotic solvent favors the forma-
tion of X, and diethyl ether, tetrahydrofuran, dimethylform-
amide, dimethyl sulfoxide and the like may be employed. Any
of the ba~es specified above to produce the dihalovinylcyclo-
propanecarboxylate, C, may be used, but the sodium or potas-
sium lower alkoxides, especially ethoxides are particularly
useful. Generally, between 1 and 2 moles of base per mole
of y~halocarboxylate are employed, for example about 1.2
moles of base per mole of y-halocarboxylate.
To conduct the process of Step 3 such that the
intermediate Y is produ~ed from the ~-halocarboxylate,
B, a polar aprotic solvent and hLgher temperatures may
generally be employed; an effective combination is sodium
ethoxide in dimethylformamide between the temperatures
of about 25 and 150C, with 50 to 150C being preferred.
Intermediate ~ may also be made from intermediate X by
heating the latter or by employing an acid in catalytic
amounts. The heat-induced isomerization can be carried
out at temperatures between about 50~ and 200C. At
temperatures below about 50C the reaction proceeds
slowly, while above 200C undesired by-products are
formed. An effective temperature range is 100 to 170C.
-30-
-` ~l23L~77~
Examples of acid catalysts which can be used to effect the
isomerization are aliphatic acids such as acetic acid, pro-
pionic acid, butyric acid, isobutyric acid and the like;
phenols such as phenol, hydroquinone and the like, and Lewis
acids such as aluminum chloride, zinc chloride and the like.
Protonic acids are generally preferred to ~ewis acids since
they giver higher yields. The acid catalyst is generally
employed in amounts ranging from about .05 to 1~ mole percent
of catalyst per mole of X. It is anticipated that the com-
bination of an acid catalyst with thermal treatment will in-
crease the rate of isomerization. It is not necessary that
the isomerization be conducted in the presence of a solvent,
but, if desired, solvents which do not adversely affect the
reaction or the product may be employed; for example, benzene,
toluene, xylene,*Tetralin, petroleum ether, dimethoxyethane,
di-(methoxyethyl)-ether and the like.
The process of Step 3 is also utilized to pre-
pare the intermediate Z from the y-halocarboxylate, B, with
sodium or potassium t-butoxide as the base, preferably in
excess with respect to the y-halocarboxylate. Solvents such
as benzene, dioxane, dimethylformamide or tetrahydrofuran
may be utilized. t-Butyl alcohol may also be used, parti-
cularly in combination with benzene. The reaction is carried
out successfully at temperatures ranging from about 25 to
50C.
To produce the dihalovinylcyclopropanecarboxy-
late, C, from any of the intermediates X, Y or Z, the condi-
tions described above for making C from the y-halocarboxy-
late, B r are employed.
-31-
* Trade Mark
77~
The practice of this invention is illustrated
further by the additional Examples which follow.
Example III
Synthesis of Eth~l 2~ -Dichlorovinyl)-
3,3-dimethylcyclopropanecarboxylate
A. Preparation of ethyl 3,3-dimethyl-4-pentenoate
A mixture of 12.9 g ~9.15 mole) of 3-methyl-2-
butene-l-ol, 48.6 g ~0.3 mole) of ethyl orthoacetate and
0.5 g of hydroquinone was heated at 140 for 20 hours with
stirring. Ethanol was removed by distillation during
the heating. At the end of 20 hours, the mixt~re was
dlstilled under reduced pressure to give, after removal
o unreacted ethyl orthoacetate, 17.6 g (75% yield) of
ethyl 3,3-dimethyl-4-pentenoate, b.p. 74-78/55 mm.
B. Addition of bromotrichloromethane to ethYl 3,3-
dimethyl-4-Pentenoate
Fifty milligrams of azobisisobutyronitrile was added
to a solution of 1.56 g (0.01 mole~ of ethyl 3,3-dimethyl-
4-pentenoate in 5 ml of brornotrichloromethane. The mix-
ture was heated for 10 hours at 130. Unreacted bromo-
trichloromethane was removed, and the residue was dis-
tilled under reduced pressure to give 3.2 g (89% yield)
of ethyl 4-bromo-6,6,6~trichloro-3,3-dimethylhexanoate,
b.p. 102-105/0.1 mm.
Analysis:
Calculated for ClOHl6BrCl3O2: C, 33.88; H, 4.55;
Found: C, 33.83; H, 4.35.
nmr ~ ppm (CCl4): 4.49 (q, lH), 4.08 (q, 2H),
3.29 (s, lH), 3.32 (d, lH), 2.42 (q, 2H), 1.35-1~13
(m, 9H)o
7~i
C. Simultaneous cyclization and dehYdrochlorination
A solution of 709 mg (2 mmoles) of ethyl 4-bromo-
6 t 6,6-trichloro-3,3-dimethylhexanoate in 5 ml of anhydrous
tetrahydrofuran was added dropwise to a suspension of
448 mg (4 mmoles) of potassium t-butoxide in 15 ml of
tetrahydrofuran, and the mixture was heated under reflux
for 2 hours. The mixture was then allowed to cool, and
an additional 220 mg of potassium t-butoxide was added.
The mixture was heated under reflux for 1 hour. Then,
another 110 mg of potassium t-butoxide was added, and
the mixture again was heated under reflux for 1 hour.
The mixture was poured into ice water and extracted with
diethyl ether. The ether extract was dried over magnesium
sulfate, the ether was removed by distillation, and the
residue was distilled under reduced pressure to give
330 mg (70% yield) of ethyl 2-(~ dichlorovinyl)-3,3-
dimethylcyclopropanecarboxylate, b.p. 86/0.5 mm.
Analysis:
nmr ~ ppm (CC14): 6.22 (d, 0.5H), 5.56 (d, 0.5H),
204.05 (b.q., 2H), 2.35-1.05 (m, llH).
ir (cm 1) 306g, 1730, 1615, 1230, 1182, 1145, 1120,
1087, 925, 860, 817, 790, 765, 702, 650.
Example IV
Synthesis of Ethyl 2-(~,~-Dibromovinyl)-
3,3-dimethylcyclopropanecarboxylate
A. Addition of carbon tetrabromide to ethvl 3,3-
dimethyl-4-pentenoate
Fifty milligrams of azobisisobutyronitrile was
added to a mixture of 1.56 g (0.01 mole) of ethyl 3,3-
30dimethyl-4-pentenoate and 3.32 g (0.01 mole) of carbon
-33-
: ~2~
tetrabromide. The mixture was heated for 5 hours at
120 under an argon atmosphere. The mixture was then
allowed to cool and was purified by column chroma-
tography with a silica gel column and a 1:1 mixture of
benzene and hexane as the eluting solvent. Concentra-
tion of the eluant gave 3 g (60% yield) of ethyl
4,6,6,6-tetrabromo-3,3-dimethylhexanoate.
Analysis:
Calculated for ClgHl6Br4O2: C, 24.62; H, 3.31; Br, 65.51;
Found: C, 24~87; H, 3.25; Br, 65.60.
nmr ~ ppm (CCl4): 4.35 (q, lH), 4.07 (q, 2H),
3.5~ (m, 2H), 2.43 (q, 2H), 1.40-1.15 (m, 9H).
B. Simultaneous c~clization and dehydrobromination
To 1.46 g of ethyl 4,6,6,6-tetrabromo-3,3-dimethyl-
hexanoate in 16 ml of absolute ethanol was added dropwise
5 ml of an ethanol solution containing 0.62 g of sodium
ethoxide. The mixture was cooled in ice throughout the
addition. The mixture was warmed to room temperature
and stirred for 6 hours. An additional 2.5 ml of
ethanolic sodium ethoxide (about 0.3 g) was added, and
the mixture was stirred for an additional 12 hours.
The mixture was then poured into ice water and extracted
with diethyl ether. The ether solution was dried over
magnesium sulfate and distilled to give 0.77 g (79% yield)
of ethyl 2~ dibromovinyl)-3,3-dimethylcyclopropane-
carboxylate, b.p. 98-101/04 mm.
Analysis:
Calculated for CloHl4Br2O2: C, 36.84; H, 4.33; Br, 49.02;
Found: C, 37.07; H, 4.40; Br, 49.27.
nmr ~ ppm (CCl4): 6.12 (d, lH), 4.08 (q, 2H),
~34-
~2~
2.20-1~40 (m, 2~), 1.37-1.10 (m, 9H).
ir (cm~l): 1725, 1223, 1175, 855, 800, 762.
Example V
~y_thesis of Ethyl 3,3-Dimethyl-4-pentenoate
A. With phenol as catalyst
A mixture of 43 g (0.5 mole) of 3-methyl-2-buten-1-ol,
97 g (0.6 mole) of ethyl orthoacetate, and 7.0 g (0.075 mole)
of phenol was heated at 135 to 140 with stirring for 9 to
10 hours~ Ethanol was distilled from the mixture as the
reaction proceeded. When the evolution of ethanol had ceased,
heating was discontinued, and the mixture was allowed to cool
to room temperature. The mixture was then dissolved in di-
ethyl ether, and the ethereal solution was treated with lN
hydrochloric acid to decompose unreacted ethyl orthoacetate~
The ethereal solution was then washed successively with a
saturated a~ueous solution of sodium bicarbonate and with
water, then dried over magnesium sulfate. The dried solu-
tion was concentrated and distilled under reduced pressure
to give 60.8 g (78% yield) of ethyl 3,3-dimethyl-4-
pentenoate, b.p. 57-60/11 mm.
Analysis:
nmr ~ ppm (CCl4): 6.15-5.60 (d.d, lH), 5.15-4.68 (m,
2H), 4.02 (q, 2H), 2.19 (s, 2H), 1.45-1.05 (m, 9H).
ir (cm~l): 3090, 1740, 1640, 1370, 1240, 1120,
1030, 995, glO.
B. With other catalysts
By the methods exemplified in Examples I-A and V-A the
following catalysts were also successfully used in the pre-
paration of ethyl 3,3-dimethyl-4-pentenoat~: boric acid,
phosphonic acid, isobutyric acid, mercuric acetate, and
-35-
q~7~
hydroquinone.
- C. Without c~talyst
A mixture of 4.3 g of 3-methyl-2-buten-1-ol and 8.1 g of
ethyl orthoacetate was heated with stirring. The temperature
was increased`slowly from room temperature to 165 over 2
hours, during which 2.21 g of ethanol was collected. The tem-
perature was maintained at 165 for 26 hours during which time
an additional 1.52 g of ethanol was collected. The reaction
mixture was then allowed to cool and diluted with diethyl
ether. The ether solution was washed successively with dilute
hydrochloric acid, saturated aqueous sodium bicarbonate and
saturated aqueous sodium chloride. The washed solution was
dried over magnesium sulfate and distilled to give 4.03 g (52%
yield) of ethyl 3,3-dimethyl-4-pentenoate, b.p. 80-85/52 mm.
D. By waY of 1,1-diethoxY-1-(3-methYl-2-buten-
l-yloxy)ethane (intermediate W)
1. Preparation of 1,1-diethoxY-1-(3-methyl-
2-buten-1-YloxY)ethane
A mixture of 4.3 g of 3-methyl-2-buten-1-ol and
16.2 g of ethyl orthoacetate was heated with stirring.
The temperature was raised slowly over 2 hours to 120,
during which time 1. R g of ethanol was evolved and re-
moved. Heating was continued at 120 for 30 minutes, and
the reaction mixture was then distilled to give, after re-
moval of 8.5 g of unreacted ethyl orthoacetate (b.p.
50-65/57 mm), 4.25 g of 1,1-diethoxy-1-(3-methyl-2-buten-
l-yloxy)ethane, b.p. 75-76/6 mm.
- Analysis:
Calculated for C~lH22O3: C, 65.31; H, 10.96;
Found: C, 65.52; H, 10.74.
-36-
776
2. Preparation of ethyl 3,3-dimethyl-4-
pentenoate
A mixture of 2.02 g of 1,1-diethoxy-1~(3- -
methyl-2-buten-1-yloxy)ethane and 20 mg of phenol was
heated for 12 hours at 150 to 160, during which time
ethanol was evolved. Distillation of the residue gave
1.12 g (72~ yield) of ethyl 3,3-dimethyl-4~pentenoate,
b.p. 80-83/57 mm.
Similarly, in the absence of phenol, 2.02 g
of 1,1-diethoxy-1-(3-methyl-2-buten-1-yloxy)ethane was
heated for 20 hours at 150 to 160. Distillation then
have 1.06 g (68% yield) of ethyl 3,3-dimethyl-4-pentenoate,
b.p. 87-89/62 mm.
Example VI
Synthesis of other y-Unsatur~ted CarboxYlates
By the methods exemplified in Examples I-A and V-A
the following ~-unsaturated carboxylates were prepared
and characterized:
A. Ethyl 2,3,3-trimethyl-4-pentenoate, b.p. 90-92/45 mm.
Analysis:
nmr ~ ppm (CCl4): 6.10-5.55 (d.d, lH), 5.10-4.70
(m, 2H), 4.05 (q, 2H), 2.25 (q, lH), 1.22 (t, 3H),
1.20-0.95 (m, 9H).
B. Ethvl 2-methvl-3~Phenvl-4-pentenoate, b.p.
104/la5 mm.
Analysis:
nmr ~ ppm (CCl4): 7.12 (b.s., 5H), 6.30-4.80 (m, 3H),
4.26-3.20 (m, 3H), 3.00-2.50 (m, lH), 1.40-0.78 (m, 6H).
C. Ethvl 2,3-dimethyl-4-pentenoate, b.p. 90-92/65 mm.
Analysis:
-37-
~2~77~i
nmr ~ ppm (CCl4): 5.85-5.37 (m, lH), 5.04-4.78 (m, 2H),
4.02 (q, 2H), 2.56~1.98 (m, 2H), 1.22 (t, 3H),
1.20-0.88 (m, 6H).
D. Methyl 2-ethyl-3,3-dimethyl-4-pentenoate,
b.p. 91-94/45 mm.
Analysis:
nmr ~ ppm (CCl4): 5.78 (d.d., lH), 5.13-4.70 (m, 2H),
3.61 (s, 3H), 2.32-1.98 (m, lH), 1.90-1.20 (m, 2H),
1.0~ (s, 6H), 0.80 (b.t~, 3H).
E. EthYl 3~henyl-4-pentenoate, b.p. 76-77/0.2 mm.
F. EthYl 3-methYl-4-pentenoate, b.p. 85-89/63 mm.
G Ethyl 2,3,3-trimethyl-4-hexenoate, b.p.
.
97-99/37 mm.
H. Ethyl 2,3,3,5-tetramethYl-4-hexenoate, b.p.
115-117/40 mm.
I. Ethyl 2,3,3-trimethYl-4-heptenoate, b.p. 120-
122/45 mm.
J. Ethyl 2,3,3-trimethyl-4-octenoate, b.p. 128-
131/40 mm.
K~ Methyl 2-ethyl-3,3-dimethYl-4-hexenoate, b.p.
97-100/30 mm.
L. Ethyl 3~3-dimethyl-4-hexenoate, b.p. 103-
105/57 mm.
M. Ethyl 3,3-dimethyl-4-heptenoate, b.p. 103-
107/38 mm.
N. Ethyl 3,3-dimethyl-4-octenoate, b.p. 114-
116/33 mm.
O. EthYl 3,3,5-trimethYl-4-hexenoate, b.p. 100-
104/45 mm.
P. Ethyl 5-cyclopentYl-3,3-dimethyl-4-pentenoate,
-38-
7~i;
b.p. 119-123/15 mm.
Q. Ethyl 3,3,6-trimethYl-4-heptenoate, b.p.
90-93/30 mm.
R. Ethyl 3,3,5-trimethyl-4-heptenoate, b.p.
100-104/20 mm.
S. BenzYl 3,3-dimethyl-4-pentenoate
In the manner of Example I-B, 810 mg of benzyl
alcohol was reacted with 1122 mg of ethyl 3,3-dimethyl-
4-pentenoate in the presence of 48 mg of sodium ethoxide
in 30 ml of toluene to give 1.0 g (65% yield) of benzyl
3,3-dimethyl-4-pentenoate, b.p. 92-98/Ool mm.
Analysis:
Calculated ~or Cl4Hl 82: C, 76.49; H, 8.51;
Found~ C, 76.79; H, 8.25.
nmr ~ ppm (~Cl4): 7.2g (b.s., 5H), 5.84 (d.d., lH),
5.05 (s, 2H), 5.05-4.70 (m, 2H), 2.22 (s, 2H), 1.06 (s, 6H).
T. By the methods exemplified above the following
~unsaturated carboxylates are prepared:
1. isopropyl 2 benzyl-3,3-dimethyl-4-pentenoate
2. t-butyl 3,3-dimethyl-4-pentenoate
3. ethyl 2-cyclopentyl-4-pentenoate
4. ethyl 3-ethyl-3-methyl-4-pentenoate
5. ethyl 3-ethyl-3-isopropyl-4-pentenoate
6. ethyl 3-t-butyl-3-propyl-4-pentenoate
7. ethyl 3-methyl-3-vinyl-4-pentenoate
8. ethyl 3-(2-butenyl)-3-ethyl-4-pentenoate
9. ethyl 2-(1-vinylcyclohexyl)acetate
10. ethyl 3-(2-butynyl)-3-methyl-4-pentenoate
11. ethyl 3-cyclohexyl-3-methyl-4-pentenoate
12. ethyl 3-benzyl-3-methyl-4-pentenoate
-39-
~2~
13. ethyl 2-benzoyl-3-carbethoxy-4-pentenoate
14. ethyl 3-acetyl-4-pentenoate
15. ethyl 3-benzoyl-4-pentenoate
16. ethyl 3-(N,N-dimethylcarboxamido)-4-
pentenoate
17. ethyl 3-(N-ethyl-N-isopropylcarboxamido)-
4-pentenoate
18. ethyl 3-cyano-2-ethynyl-4-pentenoate
19. ethyl 3-chloromethyl-4-pentenoate
20. ethyl 3-(2-bromoethyl)-4-pentenoate
21. ethyl 3-(1-fluoro-1-methylethyl)-4-
pentenoate
22. ethyl 3,3-diphenyl-4-pentenoate
23. ethyl 5-allyl-3,3-dimethy~-4-hexenoate
24. ethyl 3,3-dimethyl-5-phenyl-4-pentenoate
25. methyl 5-cyclohexyl-4-pentenoate
26. ethyl 4-cyclohexylidene-3,3-dimethyl-
butanoate
27. ethyl 5-carbomethoxy-3,3-dimethyl-4-
pentenoate
28. ethyl 5-(2~butynyl)-3,3-dimethyl-5-iso-
propoxy-4-pentenoate
29. ethyl 5-acetyl-3,3-dimethyl-4-pentenoate
30. ethyl 5-benzyl-3,3-dimethyl-4-pentenoate
31. ethyl 3,3-dimethyl-5-(N,N-dimethyl-
carboxamido)-4-pentenoate
32. ethyl 5-cyano-3,3-dimethyl-4-pentenoate
33. ethyl 5-benzoyl-3,3-dimethyl-4-pentenoate
34. ethyl 5-(2-bromoethyl)-3,3-dimethyl-4-
pentenoate
-40-
~2~ 776
35. ethyl 2,2,3,3-tetramethyl-4-pentenoate
36. ethyl 2,3,3-trimethyl-2-isopropyl-4-
pentenoate
37. ethyl 2-chloromethyl-2-phenyl-4-pentenoate
38. ethyl 3~3-dimethyl-2,2-diphenyl-4-pentenoate
39. ethyl 2-carbomethoxy-3,3-dimethyl-4-
pentenoate
40. ethyl 2-acetyl-3,3-dimethyl-4-pentenoate
41. ethyl 2-butyryl-3,3-dim~thyl-4-pentenoate
42. ethyl 3,3-dimethyl-2-(N,N-dimethylcarbox-
amido)-4-pentenoate
43. ethyl 2-cyano-3,3-dimethy~-4-pentenoate
44. ethyl l-allyl-l-cyclohexanecarboxylate
45. methyl 2-cyano-3-ethyl-4-heptenoate
46. isopropyl 5-chloromethyl-2-vinyl-4-
pentenoate
47. methyl 3-cyano-2-(N,N-dimethylcarboxamido)-
5-(2-fluoroethyl)-4-hexenoate
Example VII
Synthesis of EthYl 4,6,6,6-Tetrahalo-3,3-dimethYl-
hexanoates by Addition of Carbon Tetrahalides to
EthYl 3,3-Dimethyl-4-Pentenoates
A. Addition of carbon tetrachloride in the presence
of ferric chloride, butylamine and acetonitrile
Example II-A was repeated (1) with acetonitrile as
solvent instead of dimethylformamide and (2) without
solvent to give ethyl 4,6,6,6-tetrachloro-3,3-dimethyl-
hexanoate in 82% and 72% yield respectively.
B. Addition of carbon tetrabromide in the presence
of ferric chloride, butylamine and dimethylformamide
-41-
77~
By the method of Example II-A 3.32 g (10 mmoles)
of carbon tetrabromide was added to 1.56 g (10 mmoles)
of ethyl 3,3-dimethyl-4-pentenoate to give 2.9 g (60%
yield) of ethyl 4,6,6,6-tetrabromo-3,3-dimethylhexanoate,
b.p. 144/0.2 mm.
C. Addition of bromotrichloromethane in the presence
of ferric chloride, butYlamine and dimethylformamide
Example VII-B was repeated with 2.0 g (10 mmoles)
of bromotrichloromethane instead of carbon tetrabromide
to give 3.1 g (70% yield) of ethyl 4-bromo-6,6,6-tri-
chloro-3,3-dimethylhexanoate, b.p. 128~/0~25 mm.
D Addition of carbon tetrachloride in the presence
of ferric chloride, butylamine and dimethYlformamide
A mixture of 94.5 mg (0.35 mmole) of ferric chloride
hexahydrate, 102 mg (1.4 mmole) of butylamine, 1.2 ml of
dimethylformamide, 780 mg (5 mmoles) of ethyl 3,3-dimethyl-
4-pentenoate, and 1.54 g (10 mmoles) of carbon tetra-
chloride in a sealed tube was heated for 15 hours at
120. The contents of the tube were cooled to room
temperature and diluted with carbon tetrachloride to a
final volume of 5 ml. Gas chromatographic analysis of
the solution showed that ethyl 4,6,6,6-tetrachlGro-3,3-
dimethylhexanoate had been produced in 95% yield.
~ Other additions of carbon tetrachloride in the
presence of other salts and butvlamine
Example VII-D was repeated with each of ferrous
chloride, cuprous chloride, and cupric cyanide instead
of ferric chloride to give ethyl 4,6,6,6-tetrachloro-3,
3-dimethylhexanoate in 82%, 76%, and 72% yield (by gas
chromatographic analysis) respectively.
-42-
Repetit~on of Example VII-D with 690 mg of absolute
ethanol instead of the dimethylformamide resulted in an
80% yield of ethyl 4,6,6,6-tetrachloro~3,3-dimethyl~
hexanoate.
F, Addition of carbon tetrachloride in the Presence
of benzoyl peroxide
A mixture OL 3 .12 g ~0.02 mole) of ethyl 3~3-
dimethyl-4-pentenoate, 30 ml of carbon tetrachloride,
and 50 mg of benzoyl peroxide in a pressure vessel was
heated for 4 hours at 140. The vessel was cooled, an
additional 50 mg of benzoyl peroxide was added and the
vessel was again heated at 140 for 4 hours. After
cooling to room temperature, the mixture was washed
successively with saturated aqueous sodium bicarbonate
and water. The mixture was dried over magnesium sulfate
and distilled to give 4.56 g (74% yield) of ethyl
4,6,6,6-tetrachloro-3,3-dimethylhexanoate, b.p. 107-
108~0.3 mm.
G. Photocatalyzed addition of carbon tetrabxomide
A mixture of ethyl 3,3-dimethyl~4~pentenoate
(0.78 g) and carbon tetrabromide (3.32 g), continuously
purged with argon, was irradiated with a 200 watt
visible light source for 10 hrs. at room temperature.
The resulting dark~brown oil was purified by column
chromatography to afford 1~45 g (59.8% yield) of ethyl
4,6,6,6-tetrabromo~3,3-dimethylhexanoate.
Example VIII
Addition of Carbon Tetrahalides to
.
Other y-Unsaturated Carboxylates
A. Ethyl 4,6,6,6-tetrachloro-2,3,3-trimethyl-
-43-
~2~S~7~ii
hexanoate
A mixt~re of 1.36 g (8 mmoles) of ethyl 2,3,3-tri-
methyl-4-pentenoate, 20 ml of carbon tetrachloride, and 50
mg of benzoyl peroxide was charged into a pressure vessel.
The vessel was purged with argon, sealed and heated for
5 hours at 130 to 140. At 5-hour intervals thereafter, the
vessel was cooled, an additional 50 mg of benzoyl peroxide
was added, the reactor was rep~rged, resealed, and heating
was continued until a total of 200 mg of benzoyl peroxide
had been added and 20 hours heatiny time had elapsed. Thç
mixture was allowed to cool, then was washed successivelY
with saturated aqueous sodium bicarbonate and saturated
aqueous sodium chloride, then dried over magnesium sulfate.
Distillation gave 1.81 g (70% yield) of ethyl 4,6,6,6-tetra-
chloro-2,3,3-trimethylhexanoate, b.p. 106-107/0.3 mm.
nmr ~ ppm (CCl4): 4.43-3.85 (m, 3H), 3.45-3.00 (m, 2H),
2.97-2.63 (m, lH), 1.35-0.95 (m, 12H).
The same product was prepared (49% yield) in a similar
reaction with ferric chloride hexahydrate, n butylamine,
and dimethylformamide instead o~ benzoyl peroxide.
B~ Ethyl 4,6,6,6-tetrachlorD-3-methYlhexanoate
By the method of Example VIII-A ethyl 3-methyl-4-
pentenoate, carbon tetrachloride, and benzoyl peroxide
were reacted to give ethyl 4,6,6,6-tetrachloro-3-methyl-
hexanoate (63% yield), b.p. 103-105/0.4 mm.
Analysis:
nmr ~ ppm (CC14): 4.60-4.30 (m, lH), 4.11 (q, 2H),
3.25-3.00 (m, 2H), 2.75-2.10 (m, 3H), 1.26 (t, 3H),
1.22-0.95 (m, 3H~.
This product was also prepared in 40% yield by means
-44-
~2~ ~77~
of the ferric chloride catalyst system exemplified in
Example VII-D.
C. Eth 1 4-bromo-6 6 6-trichloro-2 3,3-trimeth 1-
Y ,, , ~,7
hexanoate
A mixture of 1.70 g (0.01 mole) of ethyl 2,3,3-tri-
methyl-4-pentenoate, 5 ml of bromotrichloromethane~ and
50 mg of benzoyl peroxide was refluxed vigorously for
10 hours in an argon atmosphere. The mixture was then
distilled to give 3.0 g (81% yield) of ethyl 4-bromo-
6,6,6~trichloro-2,3,3-trimethylhexanoate, b.p. 115--
120/0.5 mm.
Analysis:
nmr ~ ppm (CCl4): 4.60-3.80 (m, 3H), 3.70-3.10
(m, 2H), 3.10-2.70 (m, lH), 1.60~0.95 (m, 12H).
D. Eth 1 4-bromo-6,6,6-trichloro-3-me.thylhexanoate
y
By the method of Example VIII-C ethyl 3-methyl-4-
pentenoate, bromotrichloromethane, and benzoyl peroxide
were reacted to give ethyl 4-bromo-6,6,6-trichloro-3-
methylhexanoate (55% yield), b.p. 110-113/0.5 mm.
Analysis:
nmr ~ ppm (CCl4): 4.65-4.35 (m, lH), 4.14 (q, 2H),
3.45-3.10 (m, 2H), 2.65-2.10 (m, 3H), 1.24 (t, 3H),
1.25-0.95 (m, 3H).
By the method exemplified in Example VIII-A, with
benzoyl peroxide as catalyst, the following compounds
were also prepared:
E. _hyl 4,6,6,6-tetrachloro~2,3-dimethYlhexanoate,
b.p. 95-98/0.3 mm.
Analysis:
nmr ~ ppm (CCl4): 4.52-4.20 (m, lH), 4.06 (b.q, 2H),
-45-
~2~77~i
3.20-3.00 (m, 2H), 2.75-1.82 (m, 2H), 1.40-0.91
(m, 9H).
F. Ethyl 4,6,6 ! 6-tetrachloro-3-phenvlhexanoate,
b.p. 143-145/0.3 mm.
Analysis:
nmr ~ ppm (CCl4): 7.50-7.15 (m, 5H), 4.85-4.34
(m, lH), 4.33-3.80 (m, 2H), 3.78-3.42 (m, lH),
3.40-2.60 (m, 4H), 1.37-0.95 (m, 3H).
G. Ethyl 4,6,6,6-tetrachloro-2-methyl-3-PhenYl-
hexanoate, b.p. 160-165/1.0 mm.
Analysis:
nmr ~ ppm (CCl4): 7.45-7.00 (m, 5H), 4.75-4.30
(m, lH), 4.22-2.20 (m, 6H~, 1.42-0.64 (m, 6H).
H. M~t~y~_G~6,6,6-tetrachloro-2-ethv~1-3,3-dimethyl-
hexanoate, b.p. 93-97/0.2 mm.
Analysis:
nmr C ppm (CCl4): 4.10 (d.d, lH), 3.67 (s, 3H),
3.45-2.30 (m, 3~), 1.95-1.20 (m, 2~), 1.20-0.70
(m, 9H).
By the method of Example VIII-A, with the ferric
chloride hexahydrate catalyst system exemplified above,
the following compound was prepared:
I. Benzyl 4,6,6,6-tetrachloro-3,3-dimethvlhexanoate
Analysis:
Calculated for ClsHl~Cl4O2: C, 48.42; H, 4.88; Cl, 38.11;
Found: C, 48.69; H, 5.13; Cl, 38.42.
nmr ~ ppm (CCl4): 7.22 (b.s, 5H), 4.98 (s, 2H), 4.31
(d.d, lH), 3.32-2.80 (m, 2H), 2.58 (d, lH), 2.28 (d, lH),
1.17 (s, 3H), 1.08 (s, 3H).
J. By the methods exemplified above the following
-46-
~Z~77~ii
tetrahalocarboxylates are prepared:
1. ethyl 4,6,6,6-tetrachlorohexanoate
2. ethyl 4,6,6,6-tetrachloro-3-ethyl-3-
methylhexanoate
3. ethyl 4,6,6,6-tetrachloro-3-ethyl-3-
isopropylhexanoate
4. ethyl 3-t-butyl-4,6,6,6-tetrachloro-3-
propylhexanoate
5. ethyl 4,6,6,6-tetrachloro-3,3-diphenyl-
hexanoate
6. ethyl 2-[-1-(1,3,3,3-tetrachloropropyl)-
cyclohexyl]acetate
7. ethyl 4,6,6,6-tetrachloro-3-cyclobutyl-
hexanoate
8. methyl 3-benzyl-4,6,6,6-tetrachloro-
hexanoate
9. isopropyl 3-benzoyl-4,6,6,6-tetrabromo-
hexanoate
10. ethyl 3-carbethoxy-4,6,6,6-tetrachloro-
hexanoate
11. ethyl 3-acetyl-4,6,6~6-tetrachloro-
hexanoate
12. ethyl 3-butyryl-4,6,6,6-tetrachloro-
hexanoate
13. ethyl 4,6,6,6-tetrachloro-3-(N,N-di-
methylcarboxamido)hexanoate
14. ethyl 4,6,6,6-tetrachloro-3-(N-ethyl-
N-isopropylcarboxamido)hexanoate
lS. ethyl 3-cyano-4,6,6,6-tetrachloro-
hexanoate
-47-
~2~
16. ethyl 4,6,6,6-tetrachloro-3-chloromethyl-
hexanoate
17. ethyl 2-benzyl-3-(2-bromoethyl)-1,6,6,6-
tetrachlorohexanoate
18. ethyl 4,6,6,6-tetrachloro-3-(1-fluoro
l-methylethyl)hexanoate
19. ethyl 2-benzoyl-4-bromo-6,6,6-trichloro-
hexanoate
20. methyl 6,6,6-trichloro-2-cyclohexyl-4-
iodohexanoate
21. ethyl 4,6-dichloro-6,6-difluorohexanoate
22. methyl 4-bromo-6,6,6-trichloro-2,2,3,3-
tetramethylhexanoate
Z3. methyl 4-bromo-6,6,6-trichloro-2-iso-
propyl-2,3,3-trimethylhexanoate
24. isopropyl 6,6,6-trichloro-4-iodo-2-
phenylhexanoate
25. isopropyl 6,6-dichloro-6-fluoro-4-iodo-
3-methyl-2,2-diphenylhexanoate
26. ethyl 2-carbomethoxy-4,6,6,6-tetrachloro-
hexanoate
27. ethyl 2-acetyl-4,6,6,6-tetrachloro-3,3-
dimethylhexanoate
28. ethyl 2-butyryl-4,6,6,6-tetrachloro-3,3-
dimethylhexanoate
29. ethyl 4,6,6,6-tetrachloro-2-(N,N-dimethyl-
carboxamido)hexanoate
30. ethyl 4,6-dibromo-2-cyano-6,6-difluoro-
3,3-dimethylhexanoate
31. ethyl 1-(2-bromo-4,4,4-trichloro-1,1-
-48-
~2~77~
dimethylbutyl)-1-cyclohexanecarboxylate
32. t-butyl 4-bromo 6~6,6-trichloro-2-cyano-
3-ethylhexanoate
Example IX
Direct Synthesis of Ethyl 2-(~,~-Dichlorovinyl)-
3,3-dimethylcyclo~ropanecarboxylate rom Ethyl
4,6,6,6-Tetrachloro-3,3-dimethYlhexanoate
A. With potassium t-butoxide in tetrahydrofuran
A solution o~ 1.8 g (5.8 mmoles) of ethyl 4,6,6,6-tetra-
chloro-3,3-dimethylhexanoate in 2 ml of anhydrous tetrahydro-
furan was added dropwise to a suspension of 1.3 g (11.6 mmoles~
of potassium t~butoxide in 20 ml of anhydrous tetrahydrofuran.
The mixture was stirred ~or 1 hour at room temperature. An
additional 0.65 g (5.8 mmoles) of potassium t-butoxide was
then added, and the mixture was heated under reflux for 2
hours. The mixture was allowed to cool, poured into ice water,
and the aqueous mixture was extracted with diethyl ether. Af-
ter drying over magnesium sulfate, the ether solution was dis-
tilled to give 0.93 y (68% yield) of ethyl 2-(~,~-dichloro-
vinyl)-3,3-dimethylcyclopropanecarboxylate, b.p. 70-72/0.1 mm.
B. With sodium t-butoxide in tetrahydrofuran
A suspension of 2.11 g (0.011 mole) of sodium
t-butoxide in 40 ml of anhydrous tetrahydrofuran was
cooled to 0 and to the cold suspension was added drop-
wise a solution of 1.55 g (0.005 mole) of ethyl 4,6,6,6-
tetrachloro-3,3-dimethylhexanoate in 10 ml of anhydrous
tetrahydrofuran. When the addition was complete, the
mixture was stirred for 2 hours at about 0. The cold
mixture was neutralized by the addition cf a diethyl
ether solution of hydrogen chloride. The solution was
-49-
filtered and the filtrate diluted with diethyl ether.
The ether solution was washed with water, dried over
magnesium sulfate and distilled to give 1.08 g (91
yield) of a mixture of cls and rans ethyl 2~
dichlorovinyl)-3,3-dimethylcyclopropanecarboxylate,
b.p. 63-66/0.2 mm. The cis:trans ratio was found by
nmr spectroscopic analysis to be 1:1.
C. With sodium in ethanol
To a cold solution of 1.01 g (44 mmoles) of sodium
metal in 80 ml of absolute ethanol was added dropwise,
while cooling with ice, 20 ml of an ethanol solution con-
taining 6.2 g (20 mmoles) of ethyl 4,6,6,6-tetrachloro-
3,3-dimethylhexanoate. After the addition, the mixture
was stirr0d for 1 hour at room temperature, then heated
under reflux for 0.5 hour. The mixture was then cooled
to 0 and neutralized by the dropwise addition of hydrogen
chloride in ethanol. The neutral mixture was filtered,
and the filtrate concentrated to one-tenth its original
volume. The concentrated mixture was diluted with diethyl
ether, and the ethereal solution was washed successively
with saturated aqueous so~ium bicarbonate and sodium
chloride. The washed solution was dried over magnesium
sulfate and distilled to give 4.47 g (94% yield) of
ethyl 2~ dichlorovinyl)-3,3-dimethylcyclopropane-
carboxylate, b.p. 72-74/0.4 mm. The cis-trans distri-
bution was found by gas chromatographic analysis to be
34% cis, 66~ trans.
D. With potassium in ethanol
Twenty milliliters of a solution containing 3.10 g
(lO mmoles) of ethyl 4,6,6,6-tetrachloro-3,3-dimethyl-
-50-
~Z~(~776
hexanoate in absolute ethanol was added dxopwise, with
cooling, to a cold solution of 860 mg (22 mmoles) o~
potassium in 80 ml of absolute ethanol. When the addi-
tion was complete, the mixture was stirred for 1 hour
at room temperature, then heated under reflux for 0.5
hour. The mixture was treated as described in Example
IX-C to produce 2.30 g (96% yield) of ethyl 2~ di-
chlorovinyl)-3,3-dimethylcyclopropanecarboxylate which
was shown by gas chromatographic analysis to be 26% cis,
74% trans.
E. With sodium in methanol
Example IX-D was repeated using a solution of
575 mg (25 mmoles) of sodium in 80 ml of absolut;e
methanol, to which was added 20 ml of a solution of 3.1
g (10 mmoles) of ethyl 4,6,6,6-tetrachloro-3,3-dimethyl-
hexanoate in absolute methanol. The product was 2.09 g
(93% yield) of methyl 2-(~,~-dichlorovinyl)-3,3-dimethyl-
cyclopropanecarboxylate, b.p. 68-70/0.2 mm, which was
found by gas chromatographic analysis to be 23% cis,
77% trans.
F. With Potassium in methanol
Example IX-D was repeated using a solution of
860 mg (22 mmoles) of potassium in 80 ml of absolute
methanol, to which was added 20 ml of a solution of
3.1 g (10 mmoles) of ethyl 4,6,6,6-tetrachloro-3,3-
dimethylhexanoate in absolute methanol. The product
was 2.13 g (95% yield) of methyl 2-(~ dichloro-
vinyl)-3,3-dimethylcyclopropanecarboxylate which as
found by gas chromatographic analysis to be 25~ cis,
75% trans.
-51-
gl2~76
Example X
Synthesis of Ethyl 6,6,6-Trichloro-3,3-dimethYl-
4-hexenoate (an Intermediate X)
Two milliliters of a solution of anhydrous tetrahydro-
furan conta ning 709 mg (2 mmoles) of ethyl 4-bromo-6,6,6-
trichloro-3,3-dimethylhexanoate was added dropwise to a
suspension of 163 mg (2.4 mmoles) of sodium ethoxide in 20
ml of anhydrous tetrahydrofuran. The mixture was stirred at
room temperature for about 16 hours, poured into ice water
and the cold aqueous mixture was extracted with diethyl
ether. The extract was dried over magnesium sulfate and
then distilled to give 448 mg (~2% yield) of ethyl 6,6,6-
trichloro-3,3-dimethyl-4-hexenoate, b.p. 83-85/0.1 mm.
Analysis:
Calculated for CloHlsCl3O2: C, 43.90; H, 5.53; Cl, 38.87;
Found: C, 44.12; H, 5.35; Cl, 38.11.
nmr ~ ppm (CCl4): 6.13 (q, 2H), 4.07 (q, 2H), 2.29
(s, 2H), 1.50-1.00 (m, 9~).
ExamPle XI
Synthesis of Ethyl 4,6,6-Trichloro~3,3-
dimethyl-5-hexanoate (an Intermediate Y)
A. From ethyl 4,6,6,6-tetrachloro-3,3-dimethYl-
hexanoate
1. With_sodium ethoxide
A solution of 2.04 g of sodium ethoxide in
60 ml of dimethylformamide was added to a hst solution
(140) of 3.1 g of ethyl 4,6,6,6-tetrachloro-3,3-di-
methylhexanoate in 20 ml of dimethylformamide. The
mixture was maintained at 140 for 2 hours, then cooled
to 0, neutralized with dry hydrogen chloride and poured
-52-
776
into ice water. The aqueous mixture was extracted
with ether, and the extract was washed successively
with saturated aqueous sodium bicarbonate and sodium
chloride. The washed extract was dried over magnesium
sulfate and distilled to give 1.81 g (77% yield) of
ethyl 4,6,6-trichloro-3,3-dimethyl-5-hexenoate, b.p.
98-101/0.6 mm.
2. With 1,5-diazabicYclo[3.4.0]nonene-5
A solution of 1.42 g of ethyl 4,6,6,6-tetra-
chloro-3,3-dimethylhexanoate in 10 ml of anhydrous
dimethylformamide was added dropwise over 0.5 hour to
a stirred solution of 1.58 g of 1,5-diazabicylco~3.4.0]-
nonene-5 in 10 ml of anhydrous dimethylformamide maintained
at 0. The mixture was stirred for an additional 2 hours,
without cooling, poured into ice water, and the aqueous
mixture was extracted with diethyl ether. The ether
extract was washed with water, dried over magnesium
sulfate and distilled to give a liquid, b.p. 87-90/0.12
mm, found by nmr spectral analysis to consist of 800 mg
of ethyl 4,6,6-trichloro-3,3-dimethyl-5-hexenoate and
160 mg of ethyl 6,6,6-trichloro-3,3-dimethyl-4-hexenoate.
The combined yield was 88~.
B. By rearrangement of ethYl 6,6,6-trichloro-3,3-
dimethyl-4-hexenoat~ (an intermediate X)
1. By heat
A solution of 547 mg (2 mmoles) of ethyl
6,6,6-trichloro~3,3-dimethyl-4-hexenoate in 2 ml of
tetralin was heated at 150 for 24 hours under an argon
atmosphere, then distilled to give 356 mg (65% yield)
of ethyl 4,6,6-trichloro-3,3-dimethyl-5-hexenoate,
-53-
~Z~ 76
b.p. 88-90/0.2 mm.
Analysis:
Calculated for CloHlsCl3O2: C, 43.90; H, 5.53; Cl, 38~87;
Found: C, 44.18; H, 5.39; Cl, 38.65.
nmr ~ ppm (CCl4): 5.96 (d, lH), 4.85 (d, lH), 4.06
(q, 2H), 2.41 (d, lH), 2.23 (d, lH), 1.23 (t, 3H),
1.11 (s, 6H).
ir (KBr, cm~l): 1735, 1613.
The same product was also prepared in a similar
manner by heating in an inert atmo5phere either with bis (2-
methoxyethyl)ether as a solvent or without a solvent.
2. With acid catalysis
Rearrangement of this same intPrmediate X
to the same intermediate Y was also brought about (1)
by heating 547 mg of the intermediate X with 30 mg
of isobutyric acid in xylene under reflux in an argon
atmosphere for 6 hours and (2) by stirring 247 mg of
the intermediate X with 30 mg of alurninium chloride
at room temperature for 24 hours.
2~ Example XII
Synthesis of EthYl 2-(~ -Trichloroethyl)-3,3-
dimethylcycloproPanecarboxylate tan Intermediate Z)
A solution of sodium t-butoxide was prepared by
dissolving 280 mg of sodium in a mixture of 60 ml of
t-butanol and 30 ml of benzene while protecting the
mixture from moisture. To this solution was added, at
room temperature, 3.1 g (0.01 mole) of ethyl 4,6,6,6-
tetrachloro-3,3-dimethylhexanoate and the mixture was
stirred for 2 hours. Excess dry hydrogen chloride was
added, and the mixture was diluted with water and
-54-
~Z~77~
extracted with dieth~l ether. The ether extract was
washed successively with saturated aq~leous sodium bi-
carbonate and sodium chloride. The washed extract
was dried over magnesium sulfate and distilled to
give 2.03 g (74% yield) of ethyl 2~ -trichloro-
ethyl)-3,3-dimethylcyclopropanecarboxylate, b.p.
78-80/0.1 mm.
Analysi 5:
Calculated for CloHlscl3o~: C, 43.90; H, 5.53; Cl, 38.87;
Found: C, 43.80; H, 5.41; Cl, 38.87.
nmr ~ ppm (CCl4): 4.03 (d.q, 2H), 3.'-2.7 (m, 2H),
2.1-1.5 (m, 2H), 2.1-1.5 (m, 2H), 1.35 (s, 6H),
1.34 (d.t, 3H).
In a similar manner the same intermediate Z was
also prepared from ethyl 4-bromo-6,6,6-trichloro-3,3-
dimethylhexanoate.
Synthesis of Ethyl 2~ -Dichlorovinyl)-3,3-
dimethylcyclopropanecarboxYlate From
Intermediates X, Y and Z
A. From ethyl 6L6,6-trichloro-3,3-dimethyl-4-
hexenoate (an intermediate O
A solution of 410 mg of ethyl 6,6,6-trichloro-3,3-
dimethyl-4-hexenoate in 1.5 ml of anhydrous tetrahydro-
furan was added dropwise with stirring to a suspension
of 202 mg of potassium t-butoxide in 20 ml of anhydrous
tetrahydrofuran. The mixture was heated under reflux
with stirring for 3 hours, then poured into ice water.
The a~ueous mixture was extracted with diethyl ether;
the ether extract was dried over magnesium sulfate and
-55-
7~6
distilled to give 281 mg (79% yield) of ethyl 2~
dichlorovinyl)-3,3-dimethylcyclopropanecarboxylate,
b.p. 72-74/0.2 mm.
B. From ethYl 4,6,6-trichloro-3,3-dimethyl-5-
hexenoate (an intermediate Y)
1. With sodium in ethanol
A solution of 547 mg t2 mmoles of ethyl
4,6,6-trichloro-3,3-dimethyl-5-hexenoate in 2 ml of
ethanol was added dropwise with stirring to a solution
of 57 mg (2~5 mmoles) of sodium in 10 ml of absolute
ethanol. The mixture was stirred at room temperature
for S hours, cooled with ice and then neutralized by
adding a solution of hydrogen chloride in an anhydrous
ethanol. The mixture was concentrated to one-tenth
its original volume by removal of ethanol by distillation,
and 50 ml of diethyl ether was added. The mixture was
poured into ice water, the layers were separated, and
the ethereal layer was washed successively with sat-
urated aqueous sodium bicarbonate and sodium chloride.
The washed ether solution was dried over magnesium 5ul-
fate and distilled to give 436 mg (92% yield) of ethyl
2~ dichlorovinyl)-3,3-dimethylcyclopropanecarboxy-
late, b.p. 75-76/0.25 mm~ Gas chromatographic analy-
sis indicated the cis:trans ratio to bé about 2:8.
The nmr spectrum of the trans isomer was distinguished
by the absorption pattern: (~ ppm; CCl4) 5.56 (d, lH),
4.05 tb.q, 2H), 2.12 (d.d, lH), 1.47 (d, lH), 1.50-
1.10 (m, 9H); whereas specific absorption due to
the cis isomer was observed at 6.22 (d) and 2.35-
2.10 (m).
-56-
7~
2. With sodium t-butoxide in tetrahydrofuran
~ solution of 547 mg (2 mmoles) of ethyl
4,6,6-trichloro-3,3-dimethyl-5-hexenoate in 2 ml o~
dry tetrahydrofuran was added dropwise to a suspension
of 288 mg (3 mmoles) of sodium t-butoxide in lO ml of
dry tetrahydrofuran. The mixture was stirred at room
temperature for 2 hours, then poured into ice water.
The aqueous mixture was extracted with diethyl ether,
and the ether extract was dried over magnesium sulfate.
The dried extract was distilled to give 427 mg (90%
yield) of ethyl 2-(~ dichlorovinyl)-3,3-dimethylcyclo-
propanecarboxylate, b.p. 78-79/0.35 mm. Gas chromato-
graphic analy~is indi~ated the cis:trans ratio to be
about 1:9.
C. From ethvl 2-(~,B/~-trichloroethY1)-3,3-dimethyl~
cyclopropanecarboxylate ~an intermediate Z)
A solution of 2.72 g ~0.01 mole) of ethyl 2-(~
trichloroethyl)-3,3-dimethylcyclopropanecarboxylate in
20 ml of absolute ethanol was added dropwise to a solu-
tion of 250 mg (0.011 mole) of sodium in 80 ml of absolute
ethanol. The mixture was heated under reflux for 5 hours,
then cooled with ice and the cold mixture was neutralized
with dry hydrogen chloride. The mixture was concen-
trated to one tenth its original volume, then diluted
with diethyl ether. The ether solution was washed
successively with saturated aqueous sodium bicarbonate
and water. The solution was dried over magnesium sulfate
and distilled to give 1.94 g (82% yield) of ethyl 2-(~
dichlorovinyl)-3,3-dimethylcyclopropanecarboxylate, b.p.
75-76/0.25 mm.
~Z~`776
Example XIV
Synthesis of Ethyl 2~ Dibromovinvl)-
3,3-dimethylcYclopropanecarboxylate
A. Dehydrobrominati n of ethyl 4,6,6,6-tetra-
bromo-3,3-dimethylhexanoate
Two milliliters of an ethanolic solution containing
92 mg (4 mmoles) of sodium was added dropwise to a cold
solution of 1.95 g (4 mmoles) of ethyl 4,6,6,6-tetra-
bromo-3,3-dimethylhexanoate in 10 ml of absolute ethanol. ,~
The cooled mixture was stirred for 2 hours, then poured
into chilled lN hydrochloric acid. The acidic mixture
was extracted with diethyl ether, and the extract was
washed successively with saturated aqueous sodium bi-
carbonate arld sodium chloride. The washed extract was
dried over magnesium sulfate and distilled to give 846 mg
(52% yield) of ethyl 4,6,6-tribromo-3,3-dimethyl-5-
hexenoate, b.p. 130-133/0.3 mm.
~nalysis:
nmr ~ ppm (CCl4): 6.64 (d, lH), 4.95 (d, lH), 4.12
(q, 2H), 2.38 (b.d, 2H), 1.4-1.1 (m, 9H).
B. Cyclization of ethYl 4,6,6-tribromo-3,3-dimethyl-
;5-hexenoate (an intermediate Y)
A solution of 407 mg (1 mmole) of ethyl 4,6,6-tri-
bromo-3,3-dimethyl-5-hexenoate in 1.5 ml of absolute
ethanol was added dropwise to a solution of 30 mg (1.3
mmoles) of sodium in 5 ml of absolute ethanol. The mix-
ture was stirred for 3 hours at room temperature, then
treated as described in Example XIII-A to produce
270 mg (83% yield) of ethyl 2-(~,~-dibromovinyl)-3,3-
dimethylcyclopropanecarboxylate, b.p. 95-98/0.3 mm.
-58-
77~
Analysis:
nmr ~ ppm (CCl4): 6.70-6.07 (d, lH~, 4.05 (q, 2H),
2.45-1.40 (m, 2H), 1.35-1.10 ~m, 9H).
ir (cm~l): 1725, 1223, 1175, 855, 800, 762.
Example XV
Synthesis of Other 2-Dihalovinyl
cyclopropanecarboxYlates
By the methods exemplified above the following
compounds were prepared and chaxacterized:
A. EthYl 2~ -dichlorovinyl)-1,3,3-trimethYl-
cYcloproPanecarboxylate. This compound was prepared
from ethyl 4,6,6,6-tetrachloro-2,3,3-trimethylhexanoate
and had the following characteristics: b.p. 71-76/
0.08 mm.
Analysis:
nmr ~ ppm (CCl4): 6~26-5.57 (d, lH), 4.10 (b.q, 2H),
2.28-1.52 (d, lH), 1.40-0.90 (m, 12H).
This spectrum indicated that the product consisted of
30% cis and 70~ trans isomers. The trans isomer was dis-
tinguished by the absorption peaks at 5.57, 4.10, 2.28,
and 1.40-0.90, while the cis isomer was distinguished by
the absorption peaks at 6.26 and 1.52.
The same cyclopropanecarboxylate was also prepared
(1) from ethyl 4-bromo-6,6,6-trichloro-2,3,3-tri-
methyl-4-hexenoate, characterized above;
(2) from ethyl 6,6,6-trichloro-2,3,3-trimethyl-4-
hexenoate, an intermediate X having the following
characteristics: b.p. 92-95/0.2 mm.
Analysis:
nmr ~ ppm (CCl4); 6.15 (q, 2H), 4.07 (q, 2H), 2.70-
-59-
776
2.10 (m, lH), 1.30-0.90 (m, 12H);
(3) and from ethyl 4,6,6-trichloro-2,3,3-trimethyl-
5-hexenoate, an intermediate Y having the following
characteristics: b.p. 91-93/0.12 mm.
Analysis:
nmr ~ ppm (CC14): 5.95-5.94 (d, lH), 4.77-4.62 Id, lH) r
4.03-4.02 (q, 2H), 2.80-2.35 (m, lH), 1.35-O.gO (m, 12H).
B. EthYl 2~ -dichlorovinyl)-3-methYlcYclo-
propanecarbox_late
This compound was prepared from ethyl 4,6,6,6-
tetrachloro-3-methylhexanoate and had the following
characteristics: b.p. 70-77/0.5 mm.
Analysis:
ir tKBr, cm~l); 3040, 1725, 1615, 1190, 1045, 922,
883, 861, 824, 645.
The same compound was also prepared fxom ethyl 4-
bromo-6,6,6-trichloro-3-methylhexanoate and from
ethyl 6,6,6-trichloro-3-methyl-4-hexenoate (an inter-
mediate X).
C. Ethyl 2-(~,~-dichlorovinyl)-3-phenYlcyclo~
proPanecarboxylate. This compound was prepared from
ethyl 4,6,6,6-tetrachloro-3-phenylhexanoate and was
distilled at 105-115/0.1 mm. The nmr spectrum of the
product indicated that it consisted of a mixture of
isomers; the prominent nmr absorption peaks were as
follows:
(~ ppm; CCl4): 7.20 (m, 5H), 6.10 (b.d, 0.5H), 5.13
(d, 0.5H), 4.17 (b.q, 2H), 3.10-2.00 (m, 3H), 1.32
(b.t, 3H).
D. Benzyl 2-(~,~-dichlorovinyl)-3,3-dimethyl-
-60-
cyclopropanecarboxylate. This compound was prepared
from benzyl 4,6,6,6-tetrachloro-3,3-dimethylhexanoate
and had the following characteristics: b.p. 114-118/
0.13 mm.
Analysis~
Calculated for ClsHI6Cl2O2: C, 60.22; H, S.39; Cl, 23.70;
Found: C, 60.12; H, 5.39; Cl, 23.90.
nmr ~ ppm (CCl4): 7.22 (b.s, 5H), 6.18 (d, 0.5H)~
5.50 (d, 0.5H), 5.01 (s, 2H), 2.4-1.5 (m, 2H),
1.42-1.05 (m, 6~
E. By the methods exemplified above the following
cyclopropanecarboxylates are also prepared:
1. ethyl 2-(~,~-dichlorovinyl)cyclopropane-
carboxylate
2. ethyl 3-benzyl-2-(~ dichlorovinyl)cyclo-
propanecarboxylate
3. ethyl 2-(~,~-dichlorovinyl)-3-isopropyl-
3-methylcyclopropanecarboxylate
4. ethyl 1-benzoyl-3-(2-butenyl)-2-(~,~-di-
chlorovinyl)-3-ethylcyclopropanecarboxylate
5. methyl 2-(~,~-dichlorovinyl)-3-methyl-
3-phenylcyclopropanecarboxylate
6. ethyl 2~ dichlorovinyl)spiro[2.5]-
octane-l-carboxylate
7. methyl 3-allyl-3-carbomethoxy-2~ -di-
chlorovinyl)cyclopropanecarboxylate
8. methyl 3-carbomethoxy-2-(~,~-dichlorovinyl)-
3-cyanocyclopropanecarboxylate
9. ethyl 3-acetyl-1-benzyl-2-(~,~-dichloro-
vinyl)-1-cyclohexyl-3-ethylcyclopropanecarboxylate
-61-
~Z~77~ii
lO. methyl 3-benzoyl-2~ di~romovinyl)-3-
phenylcyclopropanecarboxylate
ll. ethyl 3-acetyl-2-(~,~-dibromovinyl)-3-
(N!N-dimethylcarboxamido~cyclopropanecarboxylate
12. ethyl 3-cyano-2-(~,~-difluorovinyl)-
3-methylcyclopropanecarboxylate
13. ethyl 2-(~ dichlorovinyl)-l-ethyl-3,3-
dimethylcyclopropanecarboxylate
14. isopropyl 2-(~-bromo-~-chlorovinyl)-
1,3-d~methylcyclopropanecarboxylate
15. methyl 2-(~,~-difluorovinyl)-3,3-dimethyl-
l-phenylcyclopropanecarboxylate
16. ethyl 1-vinyl-2-(~,~-dichlorovinyl)-3-
cyclohexyl-3-ethylcyclopropanecarboxylate
17. methyl 1-carboisopropoxy-2-(~,~-dibromo-
vinyl)-3,3-dimethylcyclopropanecarboxylate
18. ethyl l-acetyl-2-(~,~-dichlorovinyl)-3,3-
dimethylcyclopropanecarboxylate
l9. methyl 1-butyryl-2-(~,~-dichlorovinyl)-
3-cyanocyclopropanecarboxylate
20. ethyl 2-(B~-dibromoviny~ -(N~N-di
me~hylcarboxamido)-3-methylcyclopropanecarboxylate
21. methyl l-cyano-2-(~,~-difluorovinyl)-
3-phenylcyclopropanecarboxylate
22. ethyl l-ethynyl-2-(~,~-dichlorovinyl)-
3,3-dimethylcyclopropanecarboxylate
The use of the processes of this invention to
prepare vinylcyclopropanecarboxylates other than
dihalovinyl is exemplified by the following
examples:
-62-
12~77~
Example XVI
A. Preparation of EthYl 1,3,3-Trimeth~1-2-vinyl-
cyclopropanecarboxy~ate
1. A mixture of 920 mg (5 mmoles) of ethyl
2,3,3-trimethyl-4-hexenoate, 10 ml of carbon tetrachloride,
107 g (6 mmoles) of N-bromosuccinimide, and 50 mg of
benzoyl peroxide was heated under reflux for about two hours.
The insolublP succinimide was removed by filtration. The
filtrate was washed successively with saturated aqueous
sodium bicarbonate solution and water, then dried over mag-
nesium sulfate. The dried solution was distilled to give
1.14 g (86% yield) of ethyl 6-bromo-2,3,3-trimethyl-4-
hexenoate, b.p~ 80-81/0.3 mm.
Analysis:
nmr ~ ppm (CCl4): 5.84-5.37 (m, 2H), 4.01 (q, 2H),
3.85 (d, 2H), 2.24 (q, lH), 1.22 (t, 3H),
1.13-0.97 (m, 9H).
2. A solution of 526 mg (2 mmoles) of ethyl 6-
bromo-2,3,3-trimethyl-4-hexenoate in 2 ml of anhydrous
tetrahydrofuran was added dropwise to a suspension of 224 mg
(2 mmoles) of potassium t-butoxide in 10 ml of tetrahydro-
furan. The mixture was heated under reflux for two hours
and then allowed to cool to room temperature. An addi-
tional 116 mg (1 mmole) of potassium t-butoxide was added,
and the mixture again heated under reflux for two hours.
The reaction mixture was poured into ice water, and the
aqueous mixture extracted with diethyl ether. The ether
extract was dried over magnesium sulfate and distilled to
give 200 mg (55% yield) of ethyl 1,3,3-trimethyl-2-vinyl-
cyclopropanecarboxylate, b.p. 92-95/1.5 mm.
-63
~25~7~
Analysis
nmr ~ ppm (CCl4): 6.40-4.80 (m, 3H), 4.03 ~b.q, 2~),
2.08 (b.d, lH), 1.40-1.00 (m, 12H).
B. Preparation of Ethyl 3,3-Dimethyl-2-vinylcyclo-
~ropanecarboxylate
1. By the method of Example XVI-Al there was
prepared ethyl 6-bromo-3,3-dimethyl-4-hexenoate,
b.p. 85/0.5 mm.
ir (cm~l~: 1730, 1365, 1215, 1033, 970, 710, 590.
2. By the method of Example XVI-A2 ethyl 6-
bromo-3,3-dimethyl-4-hexenoate was converted to ethyl
3,3-dimethyl-2-vinylcyclopropanecarboxylate, b.p. 68-75/
25 mm.
ir (cm~l): 1728, 1630, 1187, 1148, 1097, 1030,
990, 902.
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