Lewis/Brønsted acid-mediated cyclization/amidation of 1,6-enynes with nitriles: access to 3-enamide substituted dihydrobenzofurans.

A novel Lewis- and Brønsted-acid mediated electrophilic addition cyclization/amidation reaction of 1,6-enynes with nitriles to synthesize 3-enamide-substituted dihydrobenzofurans has been developed. The transformation involves the addition of a Brønsted acid as the electrophilic reagent to enynes, followed by intramolecular cyclization to form cationic intermediates, and the termination of the reaction by a nitrile as a nucleophile. The main features of the reaction include high atom economy and chemoselectivity, as well as the construction of C-C/C-N bonds in one step.