Metal-Free Photocatalytic Generation and Alkynylation of Carbamoyl
Radicals: a Facile Synthesis of Alkynyl Amides
Abstract
A metal-free photocatalytic alkynylation of carbamoyl radical for facile
synthesis of alkynyl amides was described. This reaction utilized
4-carbamoyl 1,4-dihydropyridines as carbamoyl radical precursors, under
visible light irradiation, reacted with hypervalent iodine(III) reagents
through radical addition process. This protocol features well functional
group tolerance, and broad substrate scope, for direct synthesis of
alkynyl amide derivatives in good to excellent yields under mild and
redox-neutral reaction conditions. The synthetic application is further
demonstrated by the late-stage installation of alkynyl amides into the
natural product and active pharmaceutical relevant molecules. The
mechanistic studies indicated that simultaneous existance between
photoredox catalytic and direct photoexcited processes.