3,4,6-Tri:chloro-phthalic anhydride prodn. - from tetra:chloro-cyclohexadiene-di:carboxylate, useful as intermediate for pesticides, pharmaceuticals, dyes etc.

摘要

Prodn. of 3,4,6-trichlorophthalic anhydride (I) comprises treating a 3,4,5,6-tetrachlorocyclohexadiene-1,2-dicarboxylic acid ester (II) with a base at up to 200 degrees C to give a 3,4,6-trichlorophthalate ester (III). (III) is then saponified conventionally to the diacid and this converted to (I) by heating. Esp. (II) is the dimethyl ester. (I) is an intermediate for pesticides, fungicides, pharmaceuticals, dyes and plastics processing additives. Simple process gives high yields without formation of by-prods. or isomers.