Note: Descriptions are shown in the official language in which they were submitted.
Case 5542
PERFLUOROALKYLATION PROCESS
This invention relates to perfluoroalkylaromatic
compounds and more particularly to a process for preparing
them.
As disclosed in McLoughlin et al., Tetrahedron,
Vol. 25, pp. 5921-5940, 1969, Kobayashi et al.,
Tetrahedron Letters, No. 42, pp~ 4071-4072, 1979, Gassman
et al., Tetrahedron Letters, Vol. 26, No. 43, pp.
5243-5246, 1985, and U. S. Patents 3,408,411 (McLoughlin
10 et al.) and 4,439,617 (Sestanj et al.), it is known that
perfluoroalkylaromatic compounds are apt to be useful as
biologically-active compounds, surfactants, coatings,
sealants, dyestuffs, and alkyd-type resins, and they can
be prepared in various ways. Matsui et al., ChemistrY
15 Letters, 1981, pp. 1719-1720, teach that aromatic halides
may be trifluoromethylated with sodium trifluoroacetate in
the presence of cuprous iodide and a dipolar aprotic
solvent. United States patent 4,590,010 (Ramachandran et
al.) discloses the use of the technique of Matsui et al.
in trifluoromethylating 6-alkoxy-5-halo-1-cyanonaphtha-
lenes and hydrocarbyl 6-alkoxy-5-halo-1-naphthoates.
An ob~ect of this invention is to provide a novel
process for preparing perfluoroalkylaromatic compounds
7~7~
- 2 -
containing at least two carbons in the perfluoroalkyl
group.
This and other objects are attained by (A~ reacting
an aromatic bromide or iodide with at least about one
5 equivalent of a potassium perfluoroalkanoate corresponding
to the formula:
KOOC(CF2)ncF3
wherein n is an integer of at least one in the presence of
cuprous iodide and a dipolar aprotic solvent and (B) if
10 desired, subjecting the product to one or more additional
reactions to form a derivative.
Aromatic halides utilizable in the practice of the
invention are substituted and unsubstituted aromatic
iodides and bromides wherein any substituents are inert
l5 substituents (i.e., substituents that do not prevent the
reaction from occurring) such as alkyl, alkoxy, alkylthio,
aryl, aryloxy, arylthio, cyano, nitro, acylamino, alkyl-
amino, tertiary amino, sulfonamido, sulfone, sulfonyl,
phosphino, perfluoroalkyl, chloro, fluoro, ester, alde-
20 hyde, ketone, acetal, and sulfono groups. The aromaticring may be a carbocyclic ring such as a benzene,
naphthalene, or anthracene ring or a five- or six-
membered heterocyclic ring having aromatic character,
e.g., a pyridine, quinoline, isoquinoline, thiophene,
25 pyrrole, or furan ring. Exemplary of such compounds are
iodobenzene, 3-iodotoluene, 4-chloroiodobenzene, 4-
iodomethoxybenzene, l-iodonaphthalene, 3-iodoaniline,
7~7~
l-iodo-3-nitrobenzene, 2-iodothiophene, 4-iodoiso-
quinoline, 2-iodopyridine, 3-iodoquinoline, and the
corresponding bromides~
In a preferred embodiment of the invention, the
5 aromatic halide i5 a halonaphthalene corresponding to the
formula:
Q
~1
X R'
10 wherein R and R' are independently selected from chloro,
: fluoro, nitro, hydroxy, and alkyl and alkoxy substituents
containing 1-6 carbons; Q is -CN or -COOR"7 R" is satu-
rated hydrocarbyl; X is bromo or iodo; and m is 0 or 1.
The halocyanonaphthalenes and halonaphthoates
15 utilizable in the practice of the invention may be any
compounds corresponding to the above halonaphthalene
formula, but they are preferably compounds wherein m is o,
X is in the 5-position, and R is an alkyl or alkoxy
substituent in the 6-position. When the R and R'
20 substituents are alkyl or alkoxy, they are generally
straight-chain groups of 1-3 carbons or branched-chain
groups of three or four carbons, such as methyl, ethyl,
propyl, l-methylethyl, butyl, 2-methylpropyl, l,1-dimethyl-
ethyl, and the corresponding alkoxy groups, although, as
25 indicated above, larger groups such as hexyl and hexanoxy
~V~ 8~3
are also utilizable. When the halonaphthalene is an
ester, Rl' may be any saturated hydrocarbyl group (i.e., a
hydrocarbyl group that is free of aliphatic unsaturation)
but i5 preferably an alkyl, cycloalky:L, aryl, alkaryl, or
5 aralkyl group containing 1-10 carbons/ e.g., methyl,
ethyl, prapyl, cyclohexyl, phenyl, tolyl, and benzyl.
Particularly preferred halonaphthalenes are 6 alkoxy-
5-bromo-1-cyanonaphthalenes, 6-alkoxy-5-iodo-1-cyano-
naphthalenes, 6-alkoxy-5-bromo-1-naphthoates, and
10 6-alkoxy-5-iodo-1-naphthoates, especially those compounds
wherein the alkoxy groups are methoxy.
The halonaphthoates are known compounds. The
halocyanonaphthalenes are compounds that can be prepared
by cyanating the appropriately substituted tetralone,
15 e.g., 6-methoxytetralone, to form the appropriately
substituted 1-cyano-3,~-dihydronaphthalene, e.g.,
6-methoxy-1-cyano-3,4-dihydronaphthalene, aromatizing the
product in any suitable manner, and brominating or
iodinating the resultant substituted l-cyanonaphthalene by
20 known techniques.
As already mentioned, the halonaphthalene or other
aromatic halide is reacted with at least about one
equivalent of a potassium perfluoroalkanoate to form the
corresponding perfluoroalkylaromatic compound. Since
25 there does not appear to be any maximum to the number of
CF2 groups that can desirably be incorporated into the
aromatic molecule, the potassium perfluoroalkanoate
employed in the reaction may be any compound corre~ponding
to the formula KOOC(CF2)nCF3 wherein n is an integer
of at least one, and it is yenerally the salt which
5 contains the same number of CF2 groups as is desired in
the product. However, because of cost and availability
factors, as well as the fact that the reaction typically
permits the formation of at least some perfluoroalkyl-
aromatic compound containing more CF2 groups in the
10 substituent than are present in the perfluoroalkanoate,
the preferred reactants are those containing 1 16 CF2
groups, such as potassium pentafluoropropionate, hepta-
fluorobutyrate, nona~luorovalerate, tridecafluorohepta-
noate, pentadecafluorooctanoate, heptadecafluorononanoate,
15 and nondecafluorodecanoate. There does not appear to be
any maximum to the amount of salt that may be employed.
However, as a practical matter, the amount used is
generally in the range of 1-20 equivalents, preferably at
least 1.5 equivalents.
Dipolar aprotic solvents that may be utilized
include, e.g., N-methylpyrrolidone, N,N-dimethylformamide,
N,N-dimethylacetamide, hexamethylphosphoric triamide, and
dimethylsulfoxide, but the particular solvent employed
does not appear to be critical except in the sense that
25 it should have an appropriate boiling point for use at the
reaction temperatures to be utilized. The solvent is used
87^3
-- 6 --
in solvent amounts, e.g., an amount such as to provide an
organic solids concentration of up to about 15%.
The cuprous iodide may be employed in any suit-
able amount, generally an amount in the range of 0.5-5
5 equivalents.
The reaction is conducted by combining the in-
gredients in any convenient order and heating them at a
suitable temperature, conveniently reflux temperature, to
accomplish the desired perfluoroalkylation Anhydrous con-
10 ditions are preferably employed, and the temperature isgenerally in the range of 130-160C., preferably
~40-155C.
The perfluoroalkylnaphthalene products of the
preferred reaction, like their trifluoromethyl homologs,
15 can be subjected to reactions such as those taught by
Sestanj et al. Thus, e.g., (1~ a (perfluoroalkyl)cyano-
naphthalene or perfluoroalkylnaphthoate prepared by the
perfluoroalkylation reaction may be hydrolyzed to the
corresponding acid in the presence of a base such as
20 sodium or pctassium hydroxide, (2) the acid can be
halogenated, e.g., by reaction with thionyl chloride, to
form the corresponding acid halide, t2) the acid halide
may be reacted with a saturated hydrocarbyl ester of an
acid corresponding to the formula ZNHCH2COOH ~e.g.,
25 methyl, ethyl, propyl, cyclohexyl, phenyl, tolyl, or
benzyl sarcosinate, the corresponding esters of amino-
.3
acetic acids having other N-substituents (Z) containing
1-6 ~arbons, such as N-ethyl and N-propyl) to form an
amide corresponding to the formula:
O=C~N~Z)-CH2COO~"
~/ "
(CF2)n R/m
CF3
(3~ the amide may be saponified to form the corresponding
salt, then hydrolyzed to the corresponding acid, and then
- 10 thiated, e.g., with phosphorus pentasulfide or the like,
to form a thioamide corresponding to the formula:
S=C-N(Z)-CH2COOH
R [~r ~ ' ~
( IF2)n R~m
CF3
or (4) the thioamide may be prepared by thiating the amide
and then subjecting the product to the saponification and
hydrolysis steps.
The invention is advantageous in that it provides a
20 means of preparing perfluoroalkyl compounds useful in
various applications, such as surfactants, coatings,
sealants, resins, and dyestuffs, as well as biologically-
active matarials or precursors therefor.
387'3
- 8 -
The following examples are given to illustrate the
invention and are not intended as a limitation thereof.
EXAMPLE I
A suitable reaction vessel was charged with 8.1 g
5 of 6-methoxy-5-bromo-1-cyanonaphthalene, 11.8 g of CuI, 35
ml of toluene, and 55 ml of N,N-dimethylformamide. The
reaction mixture was heated to 165C. with concurrent
azeotropic removal of toluene/ water (25 ml) and then
maintained at 155C. when 11.8 g of potassium pentafluoro-
10 propionate was added. The reaction was monitored by VPC.After five hours no starting material was detected and the
reaction mixture was poured into 150 ml of water and 125
ml of methylene chloride. The two phases were filtered,
after which the organic layer was separated, washed with
15 brine, and concentrated in vacuo to provide a crude
6-methoxy-5-pentafluoroethyl-1-cyano-naphthalene (6-MPCN)
having a purity of greater than 95%.
EXAMPLE II
The crude 6-MPCN product of Example I was dissolved
20 in 135 ml of methanol and 40 ml of a potassium hydroxide
solution (4.5 g of KOH in 40 ml of water) and heatecl to
125C./70 psi for seven hours. The reaction mixture was
then worked up and acidified to yield 6.6 g of 6-methoxy-
5-pentafluoroethyl-1-naphthoic acid.
3~.3
It is obvious that many variations may be made in
the products and processes set forth above without
departing from the spirit and scope of this invention.
