Copper(I)-Catalyzed Ketone, Amine, and Alkyne Coupling for the Synthesis of 2-Alkynylpyrrolidines and -piperidines.
A Cu(I)-catalyzed coupling of a ω-chloro ketone, a primary amine, and an alkyne is described. This protocol allows for the synthesis of α-quaternary carbons in 2-alkynyl-substituted N-heterocycles. The key step is the in situ generation of a cyclic ketiminium species, which has enhanced reactivity for alkynylation compared to acyclic ketiminium species.