Preparation of cyclopropane esters

Details Preparation of cyclopropane esters Preparation of cyclopropane esters

1997-01-31

1998-03-03

Shippen, Michael L.

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic acid esters

C07C 6974

Patent

active

057236496

DESCRIPTION:

BRIEF SUMMARY
This invention relates a novel process for making certain cyclopropane esters useful in the synthesis of valuable pesticides.
Esters of 3-(2-chloro-3,3,3-trifluoroprop-1-en-1-yl)-2,2-dimethylcyclopropane carboxylic acid with for example 3-phenoxybenzyl alcohol, .alpha.-cyano-3-phenoxybenzyl alcohol and 2-methyl-3-phenylbenzyl alcohol are important insecticidal and acaricidal products, and the simple alkyl esters of this acid are important intermediates in the manufacture of such products. It is desirable to establish novel processes for the manufacture of such intermediates in order to increase the manufacturer's flexibility to respond to fluctuations in price and availability of raw materials.
In our UK patent application no.9410362.9 we disclosed a novel process which can be used in to obtain the above-mentioned acid and its esters. That process which was for preparing a lower alkyl ester of 3-(2-chloro-3,3,3-trifluoroprop-1-en-1-yl)-2,2-dimethylcyclopropane carboxylic acid, comprised the steps of
(a) reacting a compound of formula (I) with a tri-lower-alkyl orthoacetate containing up to four carbon atoms in each alkyl group in the presence of at least a catalytic amount of a acid to obtain a compound of formula (III) where R is alkyl of up to four carbon atoms, and
(b) treating said compound of formula (III) with at least one molar equivalent of a base to obtain a lower alkyl ester of 3-(2-chloro-3,3,3-trifluoroprop-1-en-1-yl)-2,2-dimethylcyclopropane carboxylic acid.
If desired the carboxylic acid itself may be obtained by the further step of subjecting said lower alkyl ester to hydrolysis.
In that process the tri-lower-alkyl orthoacetate is preferably selected from trimethyl orthoacetate and triethyl orthoacetate, and the acid used in step (a) is preferably a simple carboxylic acid such as a propionic acid or butyric acid, e.g. isobutyric acid or an alkane or arene sulphonic acid e.g. p-toluene sulphonic acid. Alternatively the reaction can be conducted in the presence of an active clay, such as a montmorillonite. Montmorillonite KSF is a particularly suitable catalyst for this process. The process is carried out at an elevated temperature preferably the reflux temperature, under conditions where alcohol generated by the process can be removed from the reaction zone. The reactants are heated for a sufficient period to obtain the desired product of formula (III).
In that process the base used in step (b) is preferably a alkali metal alkoxide, and the process may be carried out in a suitable solvent or diluent such as for example a polar aprotic solvent such as dimethylformamide or an excess of the alcohol corresponding to the alkali metal alkoxide. Sodium or potassium t-butoxide are preferred bases and the reaction is preferably carried out in dimethylformamide. Other bases such as alkali metal amides, eg sodamide, or alkali metal disilylazides, eg sodium disilylazide, nay also be used, preferably in the presence of a catalytic quantity of an alkanol such as t-butanol.
In step (a) of the that process the reaction of the compound of formula (I) with the trialkyl orthoacetate is believed to lead initially to a compound of formula (IV) where X is chloro or bromo and R is alkyl of up to four carbon atoms. It is possible to isolate the compounds of formula (IV) by heating the reactants for a sufficient time to obtain the compounds of formula (IV) but for less than a sufficient time to obtain the compounds of formula (III). The compounds of formula (IV) are believed not to have been previously described and in particular the following specific compounds are believed to be novel: and
Under the process conditions the compounds of formula (IV) undergo a rearrangement leading to the compounds of formula (III). The compounds of formula (III) are also believed not to have been described previously and in particular the following specific compounds are believed to be novel:
In a further aspect of the invention disclosed in our UK Patent application no 9410362.9 there was provided a process as defined above wherein

REFERENCES:
patent: 4113968 (1978-09-01), Mori

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