Copper-Catalyzed Tandem Amide N-Arylation and Regioselective Cyclization of 2-Alkynylbenzamides

A new approach to form iminoisocoumarins from readily available and stable 2-alkynylbenzamides was developed by using a tandem copper-catalyzed N-arylation and regioselective 6-endo-dig cyclization in the presence of diaryliodonium salts, a copper catalyst, and 2,6-di-tert-butylpyridine. The arylation occurred at the nitrogen atom rather than the oxygen atom of the amide group, the alkynyl carbon, or the benzene ring of the benzamide. Cyclization occurred through a preferential nucleophilic attack by the oxygen rather than the nitrogen atom of the amide group to produce iminoisocoumarin derivatives in good to moderate yields.