GB2025962A - Cyclopropane Derivatives - Google Patents

Abstract

Novel intermediates in the manufacture of pyrethroid insecticides have the following formula:- <IMAGE> wherein X is a halogen atom, preferably chlorine or bromine. The compound preferably has the same stereochemical form as the cyclopropane ring in (+)-3-carene. The novel intermediates can be prepared by a process which comprises oxidising 1-[2-(2,2-dihalovinyl)-3,3 dimethylcyclopropyl]-3-oxo-2-butyl acetate. The starting material is preferably derived from (+)-3-carene.

Description

SPECIFICATION Novel Intermediates in the Preparation of Cyclopropanecarboxylate Esters and Process for their Manufacture The invention relates to compounds which are useful intermediates in the preparation of cyclopropa necarboxylate esters. The invention also relates to a process for the preparation of these intermediates.

The cyclopropanecarboxylate esters are insecticidally-active compounds known as "pyrethroids" and as they combine exceptionally good insecticidal properties with a very low mammalian toxicity, they are of considerable interest to the agrochemical industry and much effort has been expended in finding economic routes to them and to their principal intermediates.

The general formula of one class of these pyrethroid compounds may be represented as follows:

where each asterisk denotes an asymmetric carbon atom: each Xis a halogen atom; and R is a member of a group of radicals known to impart insecticidal activity to the molecule, e.g. 3phenoxybenzyl or alpha-cyano-3-phenoxybenzyl.

It is known that the stereoisomeric form of the acid portion of the ester of formula I should be in the ( 1 R,cis) form for maximum insecticidal activity, i.e. the absolute configuration at carbon atom 1 is R and the two hydrogen atoms on carbon atoms 1 and 2 are in a cis relationship.

This nomenclature is known as the Elliott nomenclature and is defined in M. Elliott, A. W.

Farnham, N. F. James, P. H. Needham and D. A.

Pullman, Nature, 1974, 248, 710.

It follows, therefore, that if these stereoisomeric esters of formula I are to be prepared, either a stereospecific chemical route is required or the desired stereoisomer must be obtained from a racemic form by physical separation techniques. The latter are expensive and laborious and not readily employed on an industrial scale. The Applicant has found a stereospecific route which uses as starting material the naturally-occurring substance (+)-3carene whose formula is as follows:-

This compound is an inexpensive readily-available natural terpene and the present application relates to intermediates which can be used in a route to the ( 1 R,cis)-acid portion of the pyrethroid ester of formula I starting from (+)3-carene.

The present invention provides cyclopropane compounds of the generai formula

where X is a halogen atom, preferably chlorine or bromine. These compounds may be named 2-[2 (2,2-dihalovinyl)-3,3-dimethyl- cyclopropyl]ethylidene diacetate. Preferably the compounds of formula III are in the same stereoisomeric form as that of the cyclopropane ring present in naturally-occurring (+)-3-carene, i.e. in the (1 R,cis)-form.

The present invention also provides a process for the preparation of 2-[2-(2,2-dihaiovinyl)-3,3- dimethylcyclopropyl] ethylidene diacetate of formula Ill which compirses oxidising 1-[2-(2,2- dihalovinyl )-3,3-dimethylcyclopropyl]-3-oxo-2- butyl acetate of formula

where X is a halogen atom preferably chlorine or bromine. The oxidation is carried out in the presence of a suitable oxidising agent, for example an organic peracid such as perbenzoic acid, 3-chloroperbenzoic acid, peracetic acid and perphthalic acid. The reaction is conveniently carried out in a suitable solvent, for example chloroform or acetic acid.Alternative oxidation conditions are described in "Methoden der organischen Chemie" (Houben-Weyl) Volume VIII (1952) 559-560 and Volume VlI/2b (1976) 1984-1988.

The starting material, compound IV, is a novel compound and can be prepared by a process involving (a) the reaction of a tri(dialkylamino)phosphine or an alkyl ester of an orthophosphorous acid bis(dialkylamide) with a tetrahalomethane or a trihalomethane and (b) the reaction of the product resulting from the first step with an aldehyde of the formulas

both steps being carried out in the presence of a substantially inert solvent.

The starting material is preferably derived from naturally-occuring (+)-3-carene as this enables the process according to the invention to yield a novel intermediate of formula Ill in a stereoisomeric form which, after conversion to a pyrethroid insecticide produces the highest level of pyrethroid insecticide activity. Thus the starting material and the product of the process according to the invention is preferably in the (1 R,cis)-form.

The compound and process according to the invention are of interest as part of a multi-step process to pyrethroid insecticides, e.g. esters based on (1 R,cis)-2-(2,2-dichlorovinyl)-3,3- dimethyl-cyclopropane carboxylic acid, and the corresponding dibromo analogue.

The following Example further illustrates the invention.

Example Preparation of (1 R,cis)-2-[2-(2,2-dichloro vinyl)-3,3-di methylcyclopropyl] ethylidene Diacetate (Compound lil) The contents of a 50 ml flask charged with 1 [2-(2,2-dichlorovinyl)-3,3-dimethylcyclopropyl]- 3-oxo-2-butyl acetate (11.9 mmol, 100% 1 R,cis, both spatial configurations around C--C(O)CH,) present), chloroform (10 ml) and 3-chioro- perbenzoic acid (26 mmol) were stirred magnetically for five hours at 200 C, Then, another quantity of 3-chloroperbenzoic acid (6 mmol) was added and stirring was continued for 1 6 hours.

The reaction mixture obtained was mixed with dimethyl sulphide (2 ml), keeping the temperature at 200C, stirring was continued for 1 5 minutes, dichloromethane (30 ml) was added, the suspended material was filtered off, the filtrate was washed with two 20 ml portions of a saturated aqueous solution of sodium hydrogen carbonate and two 20 ml portions of a 10% w aqueous solution of sodium chloride. The washed organic phase was dried over anhydrous magnesium sulphate and the solvent was evaporated (2 kPa) from the dried liquid to leave a residue (2.3 g) containing compound 111(100% (1 R,cis) yield 63%). The nuclear magnetic resonance spectrum of compound Ill showed the following absorptions (using a solution of compound Ill in deuterochloroform and relative to a tetramethylsilane standard): =1.05 ppm singletK3C-C-CH3 =1.15 ppm singlet H3C-C-CH3 =2.12 ppm singlet both K3C-C(O)-0- =5.62 ppm doul;let HC=CCI, =6.86 triplet H--CC--O- mulitplets for each of the H atoms bound to the ring and for HC-CH2CH.

Claims (7)

Claims.

1. A cyclopropane compound of formula

wherein X is a halogen atom.

2. A compound according to Claim 1 in the same stereoisomeric form as that of the cyclopropane ring present in naturally-occurring (+)-3-carene.

3. A process for the preparation of a compound of formula Ill which comprises oxidising 1-[2 (2,2-dihalovinyl)-3,3-dimethyl-cyclopropyl]-3- oxo-2-butyl acetate of formula

4. A process according to Claim 3 wherein the oxidation is carried out in the presence of an organic peracid.

5. A process according to Claim 3 or 4 wherein the starting material of formula IV is in the (1 R,cis)-form.

6. A process according to Claim 3, 4 or 5 substantially as hereinbefore described with reference to the Example.

7. A cyclopropane compound of formula lil prepared by a process claimed in any one of Claims 3 to 6.