The Use of Calcium Carbide as Acetylene Source in a Three‐Component Coupling with ω‐Chlorinated Ketones and Primary Amines.

Calcium carbide was used in a CuI‐catalysed three‐component coupling with ω‐chlorinated ketones and primary amines to generate terminal 2‐alkynyl‐N‐heterocycles. The formation of an imine and the subsequent intramolecular substitution results in an active electrophilic iminium species, which can be alkynylated by in situ formed copper acetylide. A number of aliphatic primary (functionalised) amines and aliphatic or aromatic alkynes together with different alkyl‐ or aryl‐substituted γ‐ or δ‐chloroketones could be used. Simple acid–base workup instead of column chromatography can be applied to obtain the resulting 2‐alkynylpyrrolidines and 2‐alkynylpiperidines. Three strikes: Calcium carbide can be used as an acetylene source through in situ hydrolysis. It was used in a three‐component coupling with ω‐chlorinated ketones and primary amines rendering terminal cyclic propargyl amines (see scheme). [ABSTRACT FROM AUTHOR]