CA1070333A

CA1070333A - Process for the preparation of 1,1-dihalo-1,3-dienes

Info

Publication number: CA1070333A
Application number: CA251,627A
Authority: CA
Inventors: Jan H. Wevers
Original assignee: Shell Canada Ltd
Current assignee: Shell Canada Ltd
Priority date: 1975-06-02
Filing date: 1976-05-03
Publication date: 1980-01-22
Also published as: FR2313334A1; IL49689A0; NL7605738A; FR2313334B1; IT1061059B; BE842180A; DE2624340A1; IL49689A; DE2624340C2; GB1536685A; JPS51143602A; BR7603469A; CH620185A5

Abstract

ABSTRACT

A process for the preparation of a 1,1-dihalo-1,3-diene of the general formula (I) in which Hal represents a chlorine, bromine or iodine atom, and R1, R2, R3 and R4 each represents a hydrogen atom or an alkyl group, which comprises reacting a tetrahaloalkane of the general formula:

Description

~7~333 This invention relates to a process for the preparation of 1,1-dihalo-1,3-dienes from 1,1,1,3-tetrachloroalkanes.
It is known from "Collection Czechoslov. Chem. Comm." 24 (1959), 2230-6 that the reaction of 1,1,1,3-tetrachloroalkanes with alkalis such as lime in water or potassium hydroxide in ethanol, gives l,l-dichloro-1,3-dienes in low yield.
It has now been found that under certain conditions other basic reagents may be used to produce l,1-dichloro-1,3-alkadienes in higher yields.
Accordingly the invention provides a process for the preparation of a 1,1-dihalo-1,3-diene of the general formula:-1 (I) R - C = C - C = CHal2 in which Hal represents a chlorine, bromine or iodine atom and Rl, R2, R3, R4 each represents a hydrogen atom or an alkyl group, preferably of 1 to 6 carbon atoms, which comprises reacting a 1,1,1,3-tetrahaloalkane of the general formula:-Rl _ C - C - C - CHal3 (II) H Hal H
wherein Rl, R , R , R4 and Hal are as defined above with a tertiary amine at a te~perature of at least 100C.
Surprisingly, using the process of the invention two molecules of hydrogen halide are eliminated from one molecule of the compound of the formula II with formation of the compound of formula I in a yield of usually more than 80%.

The process is preferably carried out at a temperature from 150 to 200C. The reaction time is preferably from 0.5 to 5 hours.
The molar ratio of tertiary amine to 1,1,1,3-tetrahaloalkane of formula II is preferably at least 2:1, for example from 2:1 to 3:1 and in particular from 2:1 to 2.5:1.

~ - 2 -~070333 The tertiary amine may be a trialkylamine, a dialkylaniline or an optionally alkyl^ or phenyl-substituted pyridine or quinoline, the alkyl in each case being preferably of 1 to 6 carbon atoms. Quinoline is particularly preferred. The process is preferably carried out ...^;

- 2a -under atmospheric pressure usin a tertiary amine which has a boiling point at atmospheric pressure above the reaction te~perature.
The process of the invention i3 of particular interest Por the preparation o~ dichloro-4~methyl-1,3-pentadiene from 1,1,1,3-tetra-chloro-4-methylpentane. 1,1-Dichloro-4-methyl-1,3-pentadiene is a precursor o~ 2-(2,2-dichlorovinyl)-3 t 3-dimethylcyclopropanecarboxylic acid, esters Or which are pyrethrin-type insecticides (see published Netherlands patent application 7307130).
The in~ention is ~urther illustrated in ~he following Exam~les.
EXAMPLE I
A mixture of one mol of 1,1,1,3-tetrachloro-4-methylpentane and 2.5 mol Or quinoline was vigorously stirred under nitrogen for a period of two hours at a temperature of 160 C. The crude 1,1-dichloro-4-methyl-1,3-pentadiene was then distilled at 180C and atmospheric pressure. An equal volume of carbon tetrachloride was added to the distillate which was then ~iltered. The ~iltrate was washed with 25 ml o~ 0.1 N aqueous hydrochloric acid and dried over anhydrous calcium chloride. The solvent was then removed under reduced pressure to give pure 1,1-dichloro-4-methyl-1,3-pentadiene, yield 97%, ca]culated on starting 1,1,1,3-tetrachloro-4-methylpentane.
EXAMPLE II
The procedure described in Example I waY repeated using 2.2 mol Or quinoline. The same results were obtained.

EXAMPLE III
The procedure described in Example I was repeated using 2.5 mol Or tributylamine instead Or quinoline. In this case the yield of 1,1-dichloro-4-methyl-1,3-pentadiene was 85%.
EXAMPLE IV
The procedure described in Example I was repeated using 1,1,1,3-tetra-chloropentane as starting material. The yield of 1,1-dichloro-1,3-pen-tadiene obtained was 90%.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the preparation of a 1,1-dihalo-1,3-diene of the general formula:

(I) in which Hal represents a chlorine, bromine or iodine atom, and R1, R2, R3 and R4 each represents a hydrogen atom or an alkyl group, which comprises reacting a tetrahaloalkane of the general formula:

(II) wherein R1, R2, R3, R4 and Hal are as defined above with a tertiary amine at a temperature of at least 100°C.

2. A process as claimed in claim 1 in which the tertiary amine is a trialkylamine, a dialkylaniline or an optionally alkyl- or phenyl-substi-tuted pyridine or quinoline.

3. A process as claimed in claim 2 in which the tertiary amine is tri-butylamine or quinoline.

4. A process as claimed in any one of claims 1 to 3 in which the molar ratio of tertiary to compound of formula II is from 2:1 to 3:1.

5. A process as claimed in any one of the claims 1 to 3 in which the temperature is from 150° to 200°C.

6. A process as claimed in any one of claims 1 to 3 in which the com-pound of formula II is 1,1,1,3-tetrachloro-4-methylpentane.

7. A process as claimed in any one of claims 1 to 3 in which R1, R2, R3 and R4 each represents hydrogen or an alkyl group of 1 to 6 carbon atoms.