Transition metal-catalyzed bond-forming reactions at the C-H bond of heteroaromatic compounds

Abstract

Recent progress in the C-H coupling reactions of heteroaromatic compounds in our group is summarized. Coupling of thiophene derivatives occurs in the presence of a nickel or palladium catalyst with a base as an additive. Lithium /-butoxide and several magnesium amides are effective for the coupling reaction of aryl chlorides, bromides, and iodides. Coupling at the C-H bond of thiophene with thienyl halides also occurs smoothly forming a thiophene-thiophene bond. The reaction is successfully applied to the polymerization of 2-halo-3-substituted thiophenes leading to highly regioregular head-to-tail-type poly(3-substituted thiophene). The reaction of thiazole at the C-H bond (2-position) with several secondary amines induces C-H, N-H coupling with a copper catalyst.