2-CYANOHEXANOIC ACID DERIVATIVES

DERIVES D'ACIDE 2-CYANOHEXANOIQUE

English Abstract

K 250
A B S T R A C T
2-Cyanohexanoic acid derivatives having the general
formula:
<IMG>
wherein X and Y each represent a chlorine or bromine atom, Hal
represents a fluorine, chlorine or bromine atom and R1 and R2
each independently represent an alkyl group of one to four
carbon atoms, or a salt thereof.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. 2-Cyanohexanoic acid derivatives having the general formula:
<IMG> (I)
wherein X and Y each represent a chlorine or bromine atom, Hal represents
a fluorine, chlorine or bromine atom and R1 and R2 each independently
represent an alkyl group of one to four carbon atoms, or a salt thereof.
2. The compound 4,6,6,6-tetrachloro-2-cyano-3,3-dimethylhexanoic acid
and its alkali metal and ammonium salts.
3. A process for the preparation of 2-cyanohexanoic acid derivatives
of the general formula I, which comprises reacting a pentenoic acid compound
of the general formula:
<IMG> (II)
wherein R1 and R2 have the same meaning as in the general formula I, with a
tetrahalomethane compound of the general formula:
CHal2XY (III)
wherein Hal, X and Y have the same meaning as in the general formula I, in
the presence of a catalyst and in an inert solvent capable of dissolving the
reactants and the catalyst.
4. A process according to claim 3 wherein the tetrahalomethane compound
of general formula III is carbon tetrachloride.
5. A process according to claim 3 wherein the solvent is a polar
solvent.

6. A process according to claim 5 wherein the polar solvent is
acetonitrile, methylene chloride, benzene, or a tetrahalomethane compound
of general formula III.
7. A process according to claim 3, 4 or 5 wherein the catalyst is
ferric, cupric or ruthenium chloride, naphthenate, stearate or acetyl-
acetonate.
8. A process according to claim 3, 4 or 5 wherein the catalyst is
ferric or cupric chloride.
9. A process according to claim 3 wherein the reaction is carried out
in the presence of a solubilizer for the catalyst and/or a reducing agent.
10. A process according to claim 9 wherein the solubilizer is an
alkylammonium halide.
11. A process according to claim 9 wherein the reducing agent is
benzoin, hydroquinone, an aldehyde, stannous chloride or an alkali metal
sulphite.

Description

1094103
This invention relates to 2-cyanohexanoic acid derivatives which
are useful intermediates in the preparation of insecticidally-active com-
pounds.
Accordingly the invention provides 2-cyanohexanoic acid derivatives
of the general formula:
X Y
~ C ~" CH - CH2 - CHal2 (I)
R CHC(O)OH
C~
wherein X and Y each represent a chlorine or bromine atom, Hal represents a
fluorine, chlorine or bromine atom and Rl and R2 each independently represent
an alkyl group of one to four carbon atoms or a salt thereof, preferably an
alkali metal or ammonium salt.
A particularly preferred novel compound is ~,6,6,6-tetrachloro-2-
cyano-3,3-dimethylhexanoic acid, together with its alkali metal and ammonium
salts. These compounds are useful intermediates in the preparation of 2-
(2,2-dichlorovinyl)-3,3-dimethylcyclopropar.ecarboxylic acid, certain esters
of which possess insecticidal activity.
The invention also relates to a process for the preparation of the
2-cyanohexanoic acid derivatives of the general formula I, which comprises
reacting a pentenoic acid compound of the general formula:
R / CH = CH2
C (II)
R2 / CHC(O)OH
C~
wherein R and R have the same meaning as in the general formula I, with a
tetrahalomethane compound of the general formula
CHal2XY (III)
wherein Hal, X and Y have the same meaning as in the general formula I, in
the presence of a catalyst, preferably a compound of copper or iron, and a
solvent capable of dissolving the reactants and the catalyst.
- 2 -

4~ql3
Rl and R2 in the general formula II preferably represent methyl
groups. Carbon tetrachloride is the preferred compound of the general for-
mula III.
Suitable solvents for the reaction are polar solvents, for example,
acetonitrile, methylene chloride, benzene and tetrahalomethane compounds of
the general formula III; in order to use te-trahalomethane compound as a sol-
vent in the process according to the invention it will have to be used in
excess over the amount required as reactant. Mixtures of solvents may also
be used.
Examples of suitable catalysts are ferric, cupric or ruthenium
chloride, naphthenate, stearate or acetylace-tonate. Very good results have
been obtained with ferric or cupric chloride.
The process is preferably conducted in the presence of a solubil-
izer for the catalyst and/or reducing agent. Examples of compounds which
enhance the solubility of the ca-talyst in the solvent are alkylammonium
halides, for example diethylammonium chloride, di-n-butylammonium bromide,
diethylpropylammonium chloride and trioctylammonium chloride. Examples of
reducing agents are benzoin, hydroquinone, aldehydes, stannous chloride and
alkali metal sulphites.
The molar ratios of solubilizer to compound of the general formula
II and of catalyst to compound of the general formula II may vary within wide
limits. ~ery good yields of compounds of the general formula I are usually
obtained when these molar ratios are between 0.001 and 0.2.
An attractive fea-ture of theprocess according to the inven-tion is
that the carboxylic acids of the general formulae I and II do not undergo de-
carboxylation reactions to any appreciable extent.
The following Examples further illustrate the invention.
EXAMPLE I
A 250 ml glass autoclave was charged with 0.3 mol of 2-cyano-3,3-
dimethyl_4-pentenoic acid, 0.9 mol of carbon tetrachloride, o.6 mol of
-- 3 --

acetonitrile, 0.03 mol of ferric chloride, 6H2o, 0.03 mol of benzoin and
0.018 mol oP diethylammonium chloride. The contents of the au-toclave were
stirred with a turbine stirrer (620 revolutions per minute), first for two
hours at 105 C and then for 18 hours at 75C. Subsequently, the con-tents of
the flask were cooled to 22 C, 150 ml of diethyl ether was added and the so-
lution formed was washed four times with 50 ml portions of lO~w aqueous hy-
drochlorie acid to remove most of the iron salt. Then, the organic phase was
contacted with a 50 ml bed of grains of silica gel for further removal of
iron salt. The organic phase thus obtained was boiled down at 30C and 12
mm Hg. The NMR spec-trum of the residue showed that no starting acid and no
deearboxylation produets were present. The yield of 4,6,6,6-tetrachloro-2-
e~ano-3,3-dimethylhexanoic acid was more than 85%, calcula-ted on starting
acid.
The NMR spectrum of the product acid measured at 60 MHz in deutero-
chloroform solution showed the following absorptions relative to a tetra-
methylsilane standard. On the basis of -the spectrum it was established that
the acid consisted of two geometric isomers, configuration 1 and configura-
tion 2.
~, ppm2 _ configuration
1 2
CH2 lH doublet 3.42 3.18
CH2 lH single-t 4.23 4.33
CHCl lH quarte-t 4.57 4.90
HCCN lH doublet 3.58 3.58
CH3 3H singlet 1.40 1.40
CH3 3X singlet 1.53 1.53
COOH lH singlet 8.92 8.92
EXAMPLE II
The experiment of Example I was repeated, but 0.1 mol o-P 2-cyano-
303,3-dimethyl_4-pentenoic acid, 0.01 mol of ferric chloride 6 H20, 0.01 mol

of benzoin and 0. oo6 mol of diethylammonium chloride were used. The contents
of the autoclave were stirred ~or 20 hours at 98 C. The yield of 4,6,6,6-
tetrachloro-2-cyano-3,3-dimethylhexanoic acid was more than 90%, calculated .,
on starting acid.
_ 4a -
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