Visible-light-induced C2-selective trifluoromethylation of indoles catalyzed by copper-containing covalent organic frameworks

Abstract

A copper-containing covalent organic framework (Cu(II)@TPA-COF) was designed and synthesized through the condensation of tris(4-aminophenyl)amine (TAPA) and tris(4-formylphenyl)amine, and its structure and optical properties were characterized. Cu(II)@TPA-COF was used as a catalyst to develop a visible-light-induced C2-selective trifluoromethylation strategy for indole derivatives, and a series of 2-trifluoromethyl indoles were synthesized under mild and green conditions. This strategy was successfully applied to optimize the synthesis of an EP2 receptor antagonist. The experimental results indicated that Cu(II)@TPA-COF exhibits good dual-functionality in photocatalysis and transition metal catalysis. Based on the control experiments and literature, a possible reaction mechanism for visible-light-induced directed C–H activation was proposed. This strategy provides a new solution for the C–H trifluoromethylation of the C2-position of indoles.