EFFICIENT CIS-TO-TRANS ISOMERIZATION OF 1,4- DIHALOBUTENE-2

摘要

This invention relates to an efficient cis-to-trans isomerization of 1,4-dihalobutene-2 by means of a thiol or hydroyen bromide or hydrogen chloride catalyzed reaction. Said isomerization provides a high trans content greater than 90% which in turn is eminently suitable for condensation with malonic esters to provide excellent yields of dimethyl 2vinylcyclopropane-1, 1-dicarboxylate with greater than 95% purity and with substantial elimination of 3,4-dichloro-butene-1.