Divergent C-H Insertion–Cyclization Cascades of N-Allyl Ynamides

Gold carbene reactivity patterns were accessed by ynamide insertion into a C(sp³)[BOND]H bond. A substantial increase in molecular complexity occurred through the cascade polycyclization of N-allyl ynamides to form fused nitrogen-heterocycle scaffolds. Exquisite selectivity was observed despite several competing pathways in an efficient gold-catalyzed synthesis of densely functionalized C(sp³)-rich polycycles and a copper-catalyzed synthesis of fused pyridine derivatives. The respective gold–keteniminium and ketenimine activation pathways have been explored through a structure–reactivity study, and isotopic labeling identified turnover-limiting C[BOND]H bond-cleavage in both processes.