Rhodium(II)-Catalyzed Alkynyl Carbene Insertion into N–H Bonds

The first insertion of an alkynyl carbene into N–H bonds under Rh-catalysis is developed. Alkynyl hydrazone carboxylates are used as donor–acceptor carbene precursors and are exquisitely inserted into the N–H bonds of various amines, amides, and 1,2-diamines. A wide variety of 3-alkynyl 3,4-dihydroquinoxalin-2(1H)-ones and densely functionalized α-alkynyl α-amino esters are obtained in good to excellent yields. Further, chemoselective N–H insertion reactions, mechanistic studies, and various synthetic transformations for obtaining valuable heterocycles are demonstrated.