Process of preparation of alkyl esters of dl cis chrysanthemic acid
AssigneeRoussel Uclaf
InventorsMichel Franck-Neumann, Christiane Dietrich-Buchecker, Michel Miesch
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Abstract
A process for the production of an alkyl ester of dl cis chrysanthemic acid having the formula ##STR1## wherein R is an alkyl having from 1 to 6 carbon atoms, involving preparing a lithiated derivative of 2-methyl-pent-2-en-4-yne, reacting the same with an alkyl chloroformate, optionally reducing the acetylenic bond to an ethylenic bond, reacting the alkyl ester with diazo-2-propane, irradiating or heating the resultant pyrazole carboxylate and, if not previously reduced, subjecting the resultant cyclopropane carboxylate to the action of a reducing agent.
Claims10
A process for the preparation of alkyl esters of 2,2-dimethyl-3RS-(2'-methyl-1'-propenyl)-cyclopropane-1SR-carboxylic acid, or alkyl esters of dl cis chrysanthemic acid having the formula ##STR22## wherein R is an alkyl having from 1 to 6 carbon atoms consisting essentially of the steps of
- (A) reacting methyl lithium with 2-methyl-pent-2-en-4-yne in an inert organic solvent,
- (B) reacting the lithiated derivative obtained with a C.sub.1 -C.sub.6 alkyl chloroformate at a temperature below 0.degree. C. in an inert organic solvent,
- (C) recovering an alkyl ester of an unsaturated acid having the formula ##STR23## wherein R has the above assigned values and A represents a carbon to carbon bond selected from the group consisting of
- an ethylenic bond and an acetylenic bond,
- (D) reacting said alkyl ester of an unsaturated acid with diazo-2-propane at a temperature below 0.degree. C. in an inert organic solvent, to obtain when A is an acetylenic bond a mixture of compounds having the formula selected from the group consisting of ##STR24## which can be separated, and when A is an ethylenic bond, a mixture of compounds having the formula selected from the group consisting of ##STR25## which are separated, (E) subjecting the alkyl ester of formula 1,2, or mixtures thereof to irradiation and of formula 3 to irradiation and heating, and
- (F) recovering said alkyl esters of dl cis chrysanthemic acid.
Dependencies are inferred from the claim text.