Potassium tert-Butoxide-Catalyzed Synthesis of Benzofuroazepines via Cyclization of (2-Alkynylbenzyl)oxy Nitriles

Herein, we report that potassium tert-butoxide-catalyzed intramolecular anionic cyclization of (2-alkynylbenzyl)­oxy nitriles has been developed for the preparation of substituted benzofuroazepines. The effects of solvent, base, temperature, reaction time, and amount of base on the efficiency of cyclization reaction was investigated. The results led us to conclude that the reactions can be carried out simply by the addition of a catalytic amount of potassium tert-butoxide (20 mol %) to a solution of (2-alkynylbenzyl)­oxy nitriles in tetrahydrofuran at room temperature in a short reaction time. The reaction proceeded selectively through a sequential intramolecular 5-exo-dig mode followed by a 7-endo-dig mode to give the benzofuroazepines via formation of two new carbon–carbon bonds in a one-pot procedure.