FREMGANGSMAADE TIL FREMSTILLING AF 1,1-DICHLOR-ALKENER

A process for the preparation of a 1,1-dichloro-alkene of the formula in which R1 is hydrogen, or an optionally substituted alkyl, alkenyl, alkinyl, cycloalkyl, aralkyl, aralkenyl or aryl radical, and R2 is an optionally substituted alkyl, alkenyl, alkinyl, cycloalkyl, aralkyl, aralkenyl or aryl radical, or R1 and R2 together form an optionally branched and/or optionally benzo-fused hydrocarbon chain, comprising reacting a carbonyl compound of the formula with a trichloromethanephosphonic acid ester of the formula in which R3 each individually is an alkyl or phenyl radical, or together are alkanediyl, in the presence of at least an equimolar amount of magnesium. Advantageously, R1 is hydrogen, R2 is a C2 to C5 alkenyl radical or a radical of the formula Z is a cyano, acetal, carboxyl or C1 to C4 alkoxycarbonyl radical, or a radical of the formula COOM, and M is sodium or potassium, R3 each individually is a C1 to C4 alkyl or phenyl radical, or the two radicals R3 together are C2 to C5 alkanediyl, about 0.95 to 1.4 moles of the trichloromethanephosphonic acid ester and about 1.5 to 4 moles of magnesium are employed per mole of the carbonyl compound, and the reaction is carried out at a temperature between about 0 DEG and 150 DEG C. in a polar aprotic solvent. The products are known intermediates, especially for insecticides.