GB1601346A

GB1601346A - Alkadienes

Info

Publication number: GB1601346A
Application number: GB2307280A
Authority: GB
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1978-03-29
Filing date: 1978-03-29
Publication date: 1981-10-28

Description

(54) ALKADIENES (71) We, IMPERIAL CHEMICAL INDUSTRIES LIMITED, Imperial Chemical House, Millbank, London, WClP 3JF; do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by the which it is to be performed, to be particularly described in and by the following statement:- This invention relates to alkadienes useful as intermediates in the preparation of insecticides.

In our copending U.K. patent application no. 51338/77 (Serial No. 1,601,344) there are described novel intermedi-ates for pyrethroid insecticides according to the general formula:

wherein one of R1 and R2 represents a group of formula: WCF2- where W represents an atom of hydrogen, fluorine or chlorine, and the other of R and R2 represents a group of formula:

where each of X, Y and Z independently represents an atom of hydrogen, fluorine or chlorine and Q represents a lower alkoxy group containing from one to three carbon atoms. Within this group of compounds those which are preferred are those wherein R' and R2 are both trifluoromethyl groups.

These compounds of formula I can be prepared by reacting an alkadiene of formula:

with a lower alkyl ester of diazoacetic acid.

This gives rise to the required compound of formula I directly. The process is conveniently conducted using an excess of the diene as a solvent for the alkyl diazoacetate in the presence of a metallic catalyst, for example powdered copper or copper bronze.

The compounds of formulae II have not previously been described. Accordingly the present invention provides compounds of formula:

wherein R' and R2 are as defined hereinabove.

The compounds of formula II wherein R1 and R2 are both haloalkyl groups or wherein one of R1 and R2 is a haloalkyl group and the other is a methyl group may be obtained by reacting the corresponding ketone of formula:

with the ylid obtained by treating a 3,3 dimethylallyl triphenylphosphonium halide, preferably the chloride or bromide, with a suitable dehydrohalogenating agent, for example an alkyllithium compound such as n - butyllithium. The phosphonium halide may be obtained by reacting triphenyl phosphine with a 3,3 - dimethylallyl halide.

Dienes which may be obtained by this process include those of formula II wherein R' and R2 are as defined in the following table:

R1 R2 CF3 CF3 CHF2 CHF2 CF3 CHF2 CF3 CH3 CF2CI CF2Cl CHF2 CF2CI The invention is illustrated by the following Examples.

EXAMPLE 1 This Example illustrates the preparation of 1 - chloro - 1,1 - difluoro - 2 - chloro difluoromethyl- 5 - methylhexa - 2,4 diene, of formula:

(a) Preparation of 3,3 - dimethylallyl tri phenylphosphonium bromide.

A mixture of 3,3 - dimethylallyl bromide (50.0 g), triphenylphosphine (88.0 g) and dry toluene (500 ml) was stirred and heated at the reflux temperature for one hour, and then kept at the ambient temperature for 18 hours. The white precipitate of 3,3 dimethylallyl triphenylphosphonium bromide (m.p. 242"C) was collected by filtration, washed with diethyl ether and dried.

(b) Preparation of 1 - chloro - 1,1 difluoro - 2 - chlorodifluoromethyl 5 - methylhexa - 2,4 - diene.

n-Butyl lithium (65.0 ml of a 15% w/w solution in hexane) was slowly added to a vigorously stirred suspension of 3,3dimethylallyl triphenylphosphonium bromide (65.0 g) in dry petroleum ether (boiling range 30--40"C, 500 ml) at 0 C under a nitrogen atmosphere, after which the mixture was kept at the ambient temperature for 18 hours. The mixture was then cooled to 0 C, and 1,3 - dichlorotetrafluoroacetone (31.44 g) was added. The mixture was then permitted to attain the ambient temperature over a period of two hours, and the precipitate removed by filtration. The filtrate was concentrated by evaporation, until the volume was about 70 ml, and passed through a short alumina column, after which the remaining solvent was evaporated at atmospheric pressure at a temperature of 69 C. The residual liquid was subjected to fractional distillation, and the fraction boiling at 79-800C/20 mm Hg collected and identified by infra red and nuclear magnetic resonance spectroscopy as 1 - chloro - 1,1 - difluoro - 2 - chlorodifluoromethyl - 5 - methylhexa - 2,4 diene.

N.m.r. (CCl4) p.p.m. 1.88-1.94 (m,6H); 6.3 (d,lH); 7.08 (d,lH).

EXAMPLE 2 By similar procedures to that illustrated in Example 1 other dienes were prepared from the appropriate ketones, as follows:- (i) 2 - Methyl - 5- trifluoromethyl hexa - 2,4 - diene was prepared from 1,1,1 - trifluoroacetone. N.m.r. (CCl4) p.p.m. 1.76-1.82 (m,9H); 5.85-6.00 (m,lH); 6.62- 6.78 (m,lH).

(ii) 1,1 - Difluoro - 2 - chlorodifluoro methyl - 5 - methyl - hexa - 2,4 - diene was prepared from 1 - chloro 1,1,2,2 - tetrafluoroacetone.

Infra red (liquid film)-3000, 1650, 1265 cm-'.

(iii) 1,1 - difluoro - 2 - difluoro methyl- 5- methylhexa- 2,4 diene was prepared from 1,1,3,3 - tetrafluoro acetone.

N.m.r. (CCl4) p.p.m. 1.90-2.02 (m,6H); 5.65-7.10 (m,4H).

EXAMPLE 3 This Example illustrates the preparation of ethyl (+) cis/trans - 3 - (2 - hydroxy 3,3,3 - trifluoro - 2 - trifluoro - methylprop - 1 - yl) - 2,2 - dimethylcyclopropane carboxylate.

A solution of ethyl diazoacetate (9.12 g) in dichloromethane (400 ml) was added dropwise over a period of 48 hours to 5 hydroxy - 2 - methyl - 6,6,6 - trifluoro 5 - trifluoromethylhex - 2 - ene (18.9 g) in the presence of a catalytic amount of anhydrous copper (II) sulphate at 110 - 120 C.

The resultant mixture was washed with water, dried over anhydrous magnesium sulphate, and distilled to yield several fractions within the range 68-900C at 0.15 mm. N.m.r., infra red and mass spectral analysis indicated that these fractions consisted principally of the (+) - cis and (±) - trans - isomers of ethyl 3 - (2 hydroxy - 3,3,3 - trifluoro - 2 - trifluoromethylprop - 1 - yl) - 2,2 - dimethylcyclopropane carboxylate in different proportions.

N.m.r. (CDCl3) p.p.m. 1.04-1.40(m,9H); 1.55-2.43 (m, 4H): 4.00-4.37 (m,2H).

EXAMPLE 4 By the use of similar procedures to that illustrated in Example 3 the following ethyl esters of formula II were obtained from the stated dienes by reaction with ethyl diazoacetate.

(i) Ethyl (+)- cis/trans - 3 - (3,3 difluoro - 2 - difluoromethylprop 1 - en - 1 - yl) - 2,2 - dimethyl- cyclopropane carboxylate, from 1,1 - difluoro - 2 - difluoromethyl 5 - methylhexa - 2,4 - diene.

N.m.r. (CCl4) p.p.m. 1.25-1.44 (m,9H); 1.60--2.40(m,2H); 4.0-4.30 (m,2H); 5.58-7.34 (complex, 3H).

(ii) Ethyl (i) - cis/trans - 3 - (E/Z - 2 trifluoromethyl - prop - 1 - en - 1 yl)- 2,2 - dimethylcyclopropane carboxylate, from 2- trifluoro methyl- 5 - methylhexa - 2,4 diene.

N.m.r. (CCl4) p.p.m. l.llA0 (m,9H); 1.50--2.10(m,5H); 4.0--4.38 (m,2H); 5.24-6.46 (m,lH).

(iii) Ethyl (+) - cis/trans - 3 - (3 chloro - 3,3 - difluoro - 2 - chloro difluoromethylprop - 1 - en - 1 yl)- 2,2 - dimethyl cylcopropane carboxylate, from 1 - chloro - 1,1 difluoro - 2 - chlorodifluoro methyl- 5 - methylhexa - 2,4 diene.

N.m.r. (CCl4) p.p.m. 1,28-1.42 (m,9H): 1.78-2.60 (m,2H); 4.08- 4.26 (m,2H); 6.20 and 7.16 (dd, 1H).

(iv) Ethyl (+) - cis/trans - 3 - (E/Z - 3,3 - difluoro - 2 - chlorodifluoro- methylprop - 1 - en - 1 - yl) - 2,2 - dimethylcyclopropane carboxylate, from 1,1 - difluoro - 2 - chloro difluoromethyl - 5 - methylhexa - 2,4 - diene.

N.m.r. (CCl4) p.p.m. 1.24-1.52 (m,9H); 1.64-2.50 (m,2H); 3.90- 4.30 (m,2H); 5.50-7.04 (m,2H).

WHAT WE CLAIM IS: 1. A diene of formula:

wherein one of R' and R2 represents a group of formula: WCF2- where W represents an atom of hydrogen, fluorine or chlorine, and the other of R' and R2 represents a group of formula:

where each of X, Y and Z independently represents an atom of hydrogen, fluorine or chlorine.

2. A diene as claimed in Claim 1 wherein R' and R2 are independently selected from trifluoromethyl, difluoromethyl and chlorodifluoromethyl, and wherein one of R' and R2 may additionally be methyl.

3. A compound as claimed in Claim 1 wherein R' and R2 each represent the trifluoromethyl group.

4. A process of preparing a diene according to Claim 1 which comprises reacting a ketone of formula:

with the ylid obtained by dehydrohalogenation of a 3,3 - dimethylallyl triphenylphosphonium halide.

5. Compounds as claimed in Claim 1 and processes for their separation substantially as described herein with particular reference to any one of the Examples.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

N.m.r. (CDCl3) p.p.m. 1.04-1.40(m,9H); 1.55-2.43 (m, 4H): 4.00-4.37 (m,2H).

EXAMPLE 4 By the use of similar procedures to that illustrated in Example 3 the following ethyl esters of formula II were obtained from the stated dienes by reaction with ethyl diazoacetate.

(i) Ethyl (+)- cis/trans - 3 - (3,3 difluoro - 2 - difluoromethylprop 1 - en - 1 - yl) - 2,2 - dimethyl- cyclopropane carboxylate, from 1,1 - difluoro - 2 - difluoromethyl

5 - methylhexa - 2,4 - diene.

N.m.r. (CCl4) p.p.m. 1.25-1.44 (m,9H); 1.60--2.40(m,2H); 4.0-4.30 (m,2H); 5.58-7.34 (complex, 3H).

(ii) Ethyl (i) - cis/trans - 3 - (E/Z - 2 trifluoromethyl - prop - 1 - en - 1 yl)- 2,2 - dimethylcyclopropane carboxylate, from 2- trifluoro methyl- 5 - methylhexa - 2,4 diene.

N.m.r. (CCl4) p.p.m. l.llA0 (m,9H); 1.50--2.10(m,5H); 4.0--4.38 (m,2H); 5.24-6.46 (m,lH).

(iii) Ethyl (+) - cis/trans - 3 - (3 chloro - 3,3 - difluoro - 2 - chloro difluoromethylprop - 1 - en - 1 yl)- 2,2 - dimethyl cylcopropane carboxylate, from 1 - chloro - 1,1 difluoro - 2 - chlorodifluoro methyl- 5 - methylhexa - 2,4 diene.

N.m.r. (CCl4) p.p.m. 1,28-1.42 (m,9H): 1.78-2.60 (m,2H); 4.08- 4.26 (m,2H); 6.20 and 7.16 (dd, 1H).

(iv) Ethyl (+) - cis/trans - 3 - (E/Z - 3,3 - difluoro - 2 - chlorodifluoro- methylprop - 1 - en - 1 - yl) - 2,2 - dimethylcyclopropane carboxylate, from 1,1 - difluoro - 2 - chloro difluoromethyl - 5 - methylhexa - 2,4 - diene.

N.m.r. (CCl4) p.p.m. 1.24-1.52 (m,9H); 1.64-2.50 (m,2H); 3.90- 4.30 (m,2H); 5.50-7.04 (m,2H).

WHAT WE CLAIM IS: 1. A diene of formula:

wherein one of R' and R2 represents a group of formula: WCF2- where W represents an atom of hydrogen, fluorine or chlorine, and the other of R' and R2 represents a group of formula:

where each of X, Y and Z independently represents an atom of hydrogen, fluorine or chlorine.

2. A diene as claimed in Claim 1 wherein R' and R2 are independently selected from trifluoromethyl, difluoromethyl and chlorodifluoromethyl, and wherein one of R' and R2 may additionally be methyl.

3. A compound as claimed in Claim 1 wherein R' and R2 each represent the trifluoromethyl group.

4. A process of preparing a diene according to Claim 1 which comprises reacting a ketone of formula:

with the ylid obtained by dehydrohalogenation of a 3,3 - dimethylallyl triphenylphosphonium halide.

5. Compounds as claimed in Claim 1 and processes for their separation substantially as described herein with particular reference to any one of the Examples.