Process for preparing high cis 3-(2,2,2-trichloroethyl)-2,2-dimethylcyclopropane-1-carboxylates

Claim 1

A process for preparing a cis rich compound of the formula Z ##STR7## wherein R is lower alkyl or a group R 1 which is allethrolonyl, tetraphthalimidomethyl, or is represented by the formula ##STR8## wherein R 2 is hydrogen, lower alkyl, lower alkynyl, trihalomethyl, or cyano, R 3 and R 4 are independently hydrogen, lower alkyl, lower alkenyl, benzyl, phenylthio or are joined to form a methylenedioxy group attached to two adjacent ring carbon atoms of a benzene ring, and R 5 is divalent oxygen or sulfur or vinylene, which comprises contacting a compound of the formula B ##STR9## wherein R is as defined above with 1 to 3 moles per mole of B of an alkali metal tertiary alkoxide of 4 to 6 carbon atoms at a temperature of about -80° C. to about 30° C. in the presence of a solvent system comprising (a) a solvent selected from (1) an aliphatic hydrocarbon of 5 to 8 carbon atoms, (2) an aromatic hydrocarbon having 6 ring carbon atoms, optionally substituted with 1 to 3 substituents selected from alkyl of 1 or 2 carbon atoms and chlorine, (3) A tertiary alcohol of 4 to 6 carbon atoms, (4) an ether selected from diethyl ether, 1,2-dimethoxyethane, 2-methoxyethyl ether, tetrahydrofuran, and dioxane, and (5) a mixture of any of the above solvents, and (b) a dipolar aprotic cosolvent selected from (1) hexamethylphosphoramide, (2) dimethylformamide, (3) dimethylacetamide, (4) dimethylsulfoxide, and (5) N-methylpyrrolidone, the ratio of solvent to cosolvent being in the range of 20:1 to 2:1 by volume.