Note: Descriptions are shown in the official language in which they were submitted.
~ 77 ~
Back~round o the Invention
Synthetic pyrethroid esters, s~milar in structure to
naturally occurring pyre~hrin, are well known as insectlcides
of high stability and low mammalian toxicity. These synthetlc
es~ers are superior to the pyrethrins found in nature in a
number of waysO Firs~, the na~urally occurring pyrethrins are
subject to very fas~ degradation and ~heir insectici~al activity
is neu~alized by air and ligh~. Second7 the nat~lrally occurring
compounds are not available in great abunda~ce and are costly
to e~tract from their natural state. The syn~hesized variations
10 of these compounds, on the other hand~ have a higher stability9
and yet are suffic~ently degradable ~ha~ they do not present
: environmental problems. They are also resistan~ ~o light induced
oxidation. In addition, pyrethroids have a low toxicity for
mammal~ and humans, rela~ive to o~her insecticide~, while
. 15 exh~biting h~gh însect~cidal act~vi~y to a wide variety o~ insects.
. One of the methods of preparation of these synthetic
pyrethroids i~ disclosed ln P,E. BlLrt, M. Elliott9 A.W. Farn~am,
.F. Jane~, P.H. Needham, and D,A. Pullman, Pesticide Science 5,
791-799 (1974). According to this method, ethyldiazoacetat8
~ reacted with 1,1-dichloro-4-methylpenta-1,3~diene to ~orm
ethyl(~)-ci9, tran~-2,2-dimathyl-3-(2,2-dichlorov~nyl)-cyclo-
propanecarboxylate, which is then converted to the carboxyl~c
acld. The la~ter was subsequently converted to the acid chlor~de~
then reacted with 3-phenoxybenzyl alcohol ln a Schotten-Bauman~
reaction~ to produce 3-phenoxybenzyl 292-dimethyl-3-(2,2-
.~ , .
: dichlorovi~yl)-cyclopropanecarboxylate, a well known insecticidally ~:
ac~ive:pyre~hroid ester. The above-mentioned diene can b~ prepared
- -2-
' ' '':'
, . , . , . . . - ................... .
-
~ 6~
by the reaction of an appropriate sulfone with sodi~m hydroxide
in a Ramberg-Backland type rearrangement. See L. R~mberg and
B Backland, Ark;v. Kemi. Mineral. Geol., 13A, No. 27 (1940);
also Bordwell and Cooper, J, Am. Chem. Soc., 73, 5187-5190 (1951).
The process involves a large number of steps, including those
for the preparation of the sulfone, and requires the use of
costly reagents.
:
- The diene has also been prepared from chloral and
isobutylene, Farlcas, Kourim, and Sorm, Collection Czechoslov.
Chem. Commun., 24, 2230-2236 (1959), in a four-step process
involving a costly zinc elimination.
A simpler process involves the addition of carbon
tetrachloride to 3-methyl-1-butene to form 1,1~1,3~tetrachloro- ;
4-methylpentane, followed by a liquid phase dehydrochlorination
to form 1,1-dichloro-4-methyl-1,3-pentadiene. A variety of
materials are known ~o catalyze ~his or similar liquid phase
dehydrochlorinations 3 notably BF3 and FeC13, see Topchiev9
Bogomolova, and Gol'dfarb, Doklady Akad. Na~k S.S.S.R., 107,
420-3 (1956), and ~elgian Patent 621,439. These known catalytic
processes.sufer from low yields due to polymerization of the
product.
The object of this lnvention is to provide a novel
process for the dehydrohalogenation of a 1,191,3-tetrahalo-4-
methyl2entane which entails polymerization to much less an extent
than kno~ processes, and thus produces higher yields of the
desired product. ~i
-3-
.. . . , ~ . .: . .. . . . .
~ 7 8
Brief Description of the Invention
This inventioo relates to a process for the manufacture
of 1,1-dihalo-4-methyl-1?3-pentadiene which com?rises contacting
a 1,1,1~3-tetrahalo-4-methylpen~ane with a catalytic amount of
stannic chloride, and recovering the product therefrom.
Detailed Description of the Invention
In the process of the present invention~ liquid stannic
chloride, SnC14, is used as a cracking catalyst in the following
reaction: CH CH
1 3 SnC14 / 3
CX3-CH2-CHX-CH-CH3 --> CX2=CH-CH-~ + 2 ~ . .
CH3
where X is a halogen selected from the group consisting of
chlorine, bromine, and fluorîne. The four X atoms in the molecule
on the le~t hand side of the above equation may all be the same
halogen, or may comprise a combination o two diferent halogens
selected from the above group. A typical example of such a
molecule combining two different halogens is l,l,l-trichloro-3-
bromo-4-methylpen~ane. The result upon cracking this molecule
lS is 1,1-dichloro-4-methyl-1,3-pentadiene plus one mole each of
HCl and HBr. The preferred halogen, or reasons of utillty of
the ~inal product~ is chlorineO Thus, the preferred reactant
ln the above equation is 1~1,173-tetrachloro-4-methylpentane
~nother example of a reactant w~h ~wo different halogens is
~0 1~1-di~luoro-1,3-dibromo-4-methylpentane.
The term "catalytic amount" is used herein to denote
an~ amount o stannic chloride which will enhance the ?rogress
of the reaction. Reasonable reaction rates are normally achieved
: .
-4~
~ 3~;'7~7~
when the stannic chloride concentration is between about 0.25%
and about 10.0% by weight wlth respect to the 1,1,1,3-tetrahalo-
4-methylpentane. The preferred range is be~ween about 0.5%
and about 5 0% by weight.
- 5 Although the reaction temperature is not an essential
aspect of the invention, the temperature chosen will be limited
by practical considerations read~ly apparent to the skilled
practitioner. Co~siderations of economy in terms o~ heat inpu~
- and overall reaction time will dictate the lower ~emperature
limit, while the boiling points of the components will dictate
the upper temperature limit. The latter can be varied by
adjustments in the system pressure In particular, superatmos-
pheric pressures will al~ow liquid phase operation at higher
temperatures. The result will be an increased reaction rate.
In general, it will be most convenient to opera~e the reaction
at a temperature between about 120C and about 200C, pref~ably
between about 140~C and about 170C. Since both the initial
compound~ the cat~lyst and the desired end product, are in the
liquid phase, the reaction will proceed most effectively ~7hen
the system is under reluxO The hydrogen halide by-product leaves
the system as a gas, the evolution of which causes the volatili-
zation and subsequent removal from the system of some of the
catalyst, thus necessitating the use of a large initial quantity
o catalyst in the reaction mixture. The amount sf cstalyst
2S lost in this manner can be reduced by operating the system at
superatmospheric pressures3 for example, up to 25 psig. As
mentioned above, the higher pressure will have the ~urther
advan~age of inereasing the reaction rate of the reflux~ng system. . ~ ~
. ;'. ' .
' ;'
:' ..
'~
.,. . ~ . ;. - , ~ .
77~
The presenc~ of air in the system will be detrimental
to the purity of the final produc~, since air will ~orm perox1des
with the resul~ing diene~ which will in turn lead to polymeriza-
tion. During ~he cracking proces~, however, the evolution of the
hydrogen halide gas serves to sw~ep ~he air out the sys~em, and
thu~ prevent the ormation o:E the harmful peroxides. Af~er the
crack~ng proce~s ~s comple~edg it will be advantageous to add a
~tab~lizer to the system to prevent polymerization. Thi~ purpose
can be served by any of the known stabilizlng agents such 88
t-butyl catechol and Ionol~ (a~ an~ioxidant defined as a tri~
substituted phenol - product of Shell Chemical Company).
At the completion of the reaction, the product can be
recovered ~rom the reaction mixture by any of the conventional
liquid recovery techniques. Additionally, the stannic chloride~ ~-
remaining in the system can be distilled off and retained for
reuse. The most use~ul recovery techniques will be vacuum dis-
~illat~on followed by steam distillation. The latter is particul rly
useul for the separatlon of the desired diene from a~y polym~r :
formed dur~ng the reactio~.
'
The advantage o~ the stannic chloride cat~lyst over
; other known catalysts i8 th~t it enhances the progre~s o the
reaction with a minimum amount of polymerization. Yields on
th~ order o 85 to 95% are readily obtainable wi~h stannic
chlorlde but are lowered by polymerization of the product during
or subsequent to the reaction. T~e yield will be ~he highest
when polymer~zatio~ is suppre~sed in the manner indicated above.
~6-- :
~ ,
.
,
. .
The 1,1,1,3-tetrahalo-4-methylpentane referred to in
the reac~ion above can be prepared by any technique known in the
art One method of preparation is the addition reaction of a
te~rahalo methane to 3-methyl l-butene. Where the four halogens
in the resulting substituted pentane are identical, the halogens
in the tetrahalomethane are likewise identical and comprise the
same four that exist in ~he product~ The preferred tetrahalo-
methane is carbon tetrachloride. The addition reaction can also
be run wi~h a tetrahalomethane which contains ~o different types
of halogen. Examples of the latter are CC13~r and CF2Br2. In
the former case, the resulting substituted pentane is 19l ,1-
trichloro 3-bromo-4-methylpentane. In the latter l,l-dichloro-
1,3-difluoro-4-methylpentane will result. Either of these
substituted pentanes can be used in the cracking reaction
described above. A variety of catalysts are known in the art
for use in the above described addition reaction. Among these
are cuprlc chloride 7 cuprous chloride, ferric chloride, ferrous - `
chloride, ferrous chloride with benzoin, ruthenium(~ triphenyl-
phosphine complexes, organic peroxides, and cobal~ous salts.
Examples of ruthenium~ triphenylphosphine complexes are
dichlorotris(triphenylphosphine)ruthenium(II) and dichlorotetra-
lcis(triphenylphosphine)ruthenium(II).
.
The organic pero~id~ tincluding hydrogen peroxide~ are
..
defined by the ormula R-O-O-R' wherein R and R' are hydrogen
or organic radicals. These include the hydroperoxides~ where R
is hydrogen and R' is alkyl, cycloalkyl, cycloalkenyl, alkaryl,
aralkyl~ and heterocyclic of up to 12 carbon atoms; the dialkyl
peroxides, w~ere R and R9 are each alkyl of up to 12 carboo atoms;
, . ~,. . . . . . . ~ . .
-
the diaralkyl peroxides, where R and R' are each arallcyl of up
to 20 carbon atoms; the aliphatic peroxy acids ~here R is hydrogen
and R' is alkanoyL or aroyl of up to 12 carbon atoms; the peroxy
esters o~ said pero~y acids, where R is alkyl or aryl of up to
12 carbon atoms and R' is alkanoyl or aroyl of up to 12 carbon
a~oms; the diacyl peroxides, where R and R' each are alkanoyl of
up to 12 carbon atoms; the diaroyl peroxides, where R and R' each
are aroyl of up to 12 carbon a~oms as well as the dialkyl peroxy-
dicarbonateg, l-hydroxyalkyL hydroperoxides, bis(l-hydroxyalkyl)
peroxides, polyalkylidene peroxi~es, alkyl ~-hydroalkyl peroxides
and peroxy acetals
Preferred organic peroxides are those wherein ~ and R'
are hydrogen, alkyl vf 1-4 carbon atoms, aralkyl of up to 12
carbon atoms, alkanoyl of up to 12 carbon atoms, or aroyl of up
to 12 carbon atoms
: Any cobaltous salt soluble in the tetrahalomethane
used will be sui~able in the addition reaction. Such salts
include cobaltous hexamine naphthalene ~ -sulfonate, cobaltous
hexamine picrate, and the various cobaltous alkylated-naphthalene
~20 sul~onates, for example, cobaltous methyl naphthalenesulfonate
and cobaltous ethyl naphthalenesulfonate.
.
The following examples are of~ered to illustrate the
process of the invention, and are not intended to impose ~ -
limitations thereon.
EXAMPL~ I
~5 A 12-ounce aerosol compatibility tube was charged with
` tha following:
.
-8--
:;
.
~ 6~7
175 ml (1.75 moles) CCl~
0.2002 g dichlo~o~ris(triphenyl-
phosphine)ruthenium(II)
105 g (l.S moles) 3-methylbutene
The air in the tube was displaced and the tube was placed in a
bath at 75C for 20 hours with sti ring. The tube and contents
were then cooled3 and the unreacted CC14 and 3-methylbutene were
removed by distillation~ leaving 286 g (85% yield) of 1,1,~,3-
tetrachloro-4-methylpentane, with 96% purity.
A stirred reaction flask with reflux condenser was . .
charged with 508 g (4.00 ml, about 2.3 moles) o~ 1,1,1,3-tetra-
chloro-4-methylpentane prepared by the above procedure, and 10 ml
of SnC14. The system was heated to reflux ~or four hours. 0 :~.
the starting material~ 5/0 remained uncracked. Steam distillation
of the product yielded 310 g (88% yield) of 1,1-dichloro-4-methyl-
.
1, 3-pentadiene, with an assay by chromatography of 97%.
' . ': ' .
EXAMPLE II
A 2-liter reactor was charged with 1288 g (1 lîter,
5.75 moles) of 1,1,1~3-tetrachloro-4-methylpentane, prepared ~n
~. .
a manner s~m~lar to that descr;bed in Example I, and 25 ml SnC14. .
The system was re1uxed at 170C. During reflux, gas chr~ma~o
20 graphy analyses provided the follo~;Lng data: :
Reaction Time % Cracked
- ,
I 1 1/4 hours 29
~ ~ ,. . .
3 1/4 hours 65
5 114 hours 85.5
.6 1/4 hours go
,
'' ' '
.. .. . . . . . . .. . .. . . . . . . ~. . . .... ~ .. :. .. . .. . . . . . .
~ ;'7~ ~
The produc~ was vacuum distilled to yield 758 g of the
diene in the distilLate. To ~he residue was added 150 ml con-
centrated HCl diluted ~7ith ~7ater to 400 ml. The residue was then
s~eam distilled to yield an additional 61 g of the diene, to
make a total o~ 819 g (94% yield), identity confirmed by gas
chromatographic analysis.
EXAIV~LE III
This example illustrates ~he results achieved when
ferric chloride rather than stannic chloride is used as the
cracking catalyst. The advantages of the stannic chlorid~ pro-
cess are apparent from the data below.
A 500 ml reactor equipped with stirrer and condenser
was charged with 200 ml (256 g, 1.14 moles) of 1,1,1,3-tetrachloro-
4-methyl-pentane, and 10 g of FeC13. The mixture was
heated to reflux at about 160C. After about 1 hour, the reaction
mixture formed a thick gel. A solution of 40 ml concentrated
HCl diluted to 100 ml with dis~illed water was added to the gel9
snd the mixture was steam distilled. Of a possible 170 g
(theoretical amount), onLy llL g of unpolymeriæed material was
recovered. Of this amount, 47.5% was the uncracked starting
material, and 34.4~O was the desired produc~. Conversion was
66~/o~ with a yield of 35%.
10~
.
: .. . . . .. . . - . .
