Process of preparing dihalovinyl compounds

A process for the preparation of a compound of the formula I ##STR25## wherein R.sup.1 represents a 2-(2,2-dimethoxyethyl)-3,3-dimethylcyclopropyl group, or a 2,2-dimethyl-3-alkoxycarbonylcyclopropyl) group in which the alkoxy group has fewer than five carbon atoms, R.sup.2 a hydrogen atom and each Hal stands for a chlorine atom, which comprises contacting a trihalomethyl compound of the formula II ##STR26## wherein R.sup.1, R.sup.2 and Hal have the same meaning as in formula I and X represents a group --PQ.sub.2, ##STR27## wherein Q represents a halogen atom and R.sup.3 and R.sup.4 both represent an alkyl group with fewer than ten carbon atoms with zinc and an alkanoic acid with fewer than 5 carbon atoms per molecule.