NEW MATERIAL: An aryl 4-cyano-2,2,4-trichlorobutyrate represented by formula I [wherein Ar is a (substituted) aryl or a (substituted) haloaryl].

EXAMPLE: Phenyl 4-cyano-2,2,4-trichlorobutyrate.

USE: A novel starting material useful for the preparation of 3,4,6- trichloropyraidin-2-ol represented by formula II and a salt thereof to be used as an intermediate for preparing a herbicide, a fungicide and an insecticide in high purity and in high yield advantageously on an economic and industrial scale.

PREPARATION: An aryl trichloroacetate of formula III and acrylonitrile are reacted in a polar aprotic solvent such as sulfolane in the presence of a catalytic amount of a metal selected from a main transition metal series metal, a subgroup IB or IIB metal, salt thereof or an oxide thereof such as Cu2Cl2 at 80-180°C to obtain the objective compound of formula I.