To a stirred and cooled (5-10 degrees C) mixture of 15.2 parts of 4-amino-2,6-dichloro-α-(4-chlorophenyl)-benzeneacetonitrile (intermediate 2), 14.4 parts of concentrate hydrochloric acid and 125 parts of acetic acid is added dropwise, during a 30 minutes period, a solution of 3.5 parts of sodium nitrite in 15 parts of water at about 10 degrees C. Upon completion, the whole is stirred for 30 minutes and then 10 parts of sodium acetate and 7.8 parts of ethyl(2-cyanoacetyl)carbamate are added, during a period of 2 hours, at room temperature. The reaction mixture is poured into 500 parts of water. The product is filtered off, washed with water and dissolved in dichloromethane. The organic layer is dried, filtered and evaporated. The residue is purified by column chromatography over silica gel using a mixture of trichloromethane and methanol (95:5 by volume) as eluent. The pure fractions are collected and the eluent is evaporated in vacuo. The residue is stirred in 2-propanol. The product is filtered off, washed with 2,2'-oxybispropane and dried, yielding ethyl[2-[[3,5-dichloro-4-[(4-chlorophenyl)cyanomethyl]phenyl]hydrazono]-2-cyanoacetyl]carbamate (intermediate 3).
