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.