Merging decatungstate photocatalysis and copper‐catalyzed azide‐alkyne cycloaddition reaction for the formation of 1,2,3‐triazoles in water†

Abstract

Merging photoredox and catalysis by transition metals, coined as metallaphotoredox catalysis, proved to be an excellent new platform for the development of new synthetic strategies for the formation of carbon–carbon and carbon‐heteroatom bonds. Herein, we report a dual catalytic system that has been successfully developed for the azide‐alkyne ligation process to yield 1,4‐disubstituted‐1,2,3‐triazoles. It consists of merging the decatungstate anion [W10O32]4−‐photocatalyzed hydrogen atom transfer from ethanol as a source of hydrogen atom abstraction to produce the one‐electron‐reduced form H+[W10O32]5−, which reduces Cu(II) precursor into Cu(I) starting then the copper‐catalyzed azide‐alkyne cycloaddition reaction (CuAAC). The resulting bifunctional H+[W10O32]5−/Cu catalytic system operates efficiently in an environmentally benign water–ethanol solvent mixture as reaction medium, resulting in the regioselective formation of 1,4‐disubstituted‐1,2,3‐triazole derivatives, with high yields up to 99% and large substrate application scope under mild conditions. This dual catalytic approach has proven to function under sunlight exposition too with recovery and reuse of the catalytic system for several times.