Homocoupling of a Grignard Reagent toward the Synthesis of 2,2′-Bis(trifluoromethyl)-4,4′-diaminobiphenyl

A new process for the synthesis of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB) comprising three steps has been industrially developed. The first step is the homocoupling of the Grignard reagent derived from 1-chloro-2-(trifluoromethyl)benzene with iron chloride(III) in the presence of an oxidizing agent to afford 2,2'-bis(trifluoromethyl)biphenyl. The second step is the nitration of this biphenyl to 2,2'-bis(trifluoromethyl)-4,4'-dinitrobiphenyl, and the third step is the reduction of this dinitrobiphenyl using hydrogen over Pd/C to afford TFMB. This process has been demonstrated on an industrial scale.