Chemoselective transfer hydrogenation of alkynoates enabled by Cu(I)-photosensitizer catalysis

Abstract

Hydrogenation reactions are of great value in synthetic chemistry, however, it has been challenging to distinguish the reactivity of various reactive motifs. Herein, we report a novel strategy for the transfer hydrogenation of alkynes to alkanes enabled by Cu(I) photosensitizer catalysis. This photoredox protocol creatively employs Hantzsch ester/tertiary amine as the reductant and hydrogen source. More importantly, it enables the highly chemoselective functionalization of alkynoates in the presence of other reactive motifs, such as benzyl esters, pyridines, and even electron-neutral alkynes, thus establishing complementary approach to all the previous alkyne hydrogenation methodologies.