Copper‐Catalyzed Three‐Component Synthesis of 2‐Iminodihydrocoumarins and 2‐Iminocoumarins

An efficient synthesis of N ‐sulfonyl‐substituted 2‐imino‐3,4‐dihydrocoumarins and 2‐iminocoumarins via a copper‐catalyzed multicomponent reaction of sulfonyl azides with terminal alkynes and β‐( ortho ‐hydroxyphenyl)‐α,β‐unsaturated ketones or ortho ‐hydroxyphenylpropiolates has been developed. The cascade process involves trapping the keteimine by a nucleophilic addition and an intramolecular Michael addition. This methodology could well be extended to the concise synthesis of the polysubstituted piperidine scaffold.