Preparation of lower alkyl esters of 3-(2-chloro-3,3,3-trifluoroprop-1-en-1-yl)-2,2-dimethyl cyclopropanecarboxylic acid

摘要

A process for the preparation of a lower alkyl ester of 3-(2-chloro-3, 3, 3-trifluoropropl-en-l- yl)-2,2-dimethylcyclopropane carboxylic acid where lower alkyl means alkyl of up to four carbon atoms which comprises the steps of: (a) reacting a compound of the formula CF3CHXCl (II) wherein X is chloro or bromo, with 3-methylbut-2-en-l-al in the presence of a strong base and an inert solvent to prepare a compound of formula CF3-CXCl-CH(OH)-CH=C(CH3)2(I) wherein x is chloro or bromo; (b) reacting a compound of formula (I) wherein X is chloro or bromo, 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 an active clay at an elevated temperature for a sufficient time to obtain a compound of formula CF3-CXCl-CH=CH-C(CH3)2-CH2CO2R(III) wherein R is an alkyl group containing up to four carbon atoms, and (c) treating said compound of formula (III) with at least one molar equivalent of a base to obtain said alkyl ester of 3-(2-chloro-3, 3, 3-trifluoroprop-1-en-l-yl)-2, 2-dimethyl- cyclopropane carboxylic acid. 398 י" ג בתמוז התש" ס - July 16, 2000