| abstract |
A process for the preparation of a 3-(2,2-dichlorovinyl)-2,2-dimethyl-cyclopropane-1-carboxylic acid or derivative of the formula ##STR1## in which R is hydrogen, alkali metal, ammonium, an equivalent of an alkaline earth metal, alkyl, or a radical customary in the alcohol part of pyrethroids, n comprising reacting a 3-formyl-2,2-dimethyl-cyclopropane-1-carboxylic acid derivative of the formula ##STR2## with a dichloromethane derivative of the formula ##STR3## in which R 1 and R 2 each independently is alkyl, phenyl, alkoxy or phenoxy, or together are alkanediyl or alkanedioxy, n in the presence of a base at a temperature between about -50° and +50° C. The products are intermediates for the preparation of esters of pyrethroid-like insecticidal activity. |