Copper-Catalyzed Synthesis of Azaspirocyclohexadienones from α-Azido-N-arylamides under an Oxygen Atmosphere

A copper-catalyzed reaction of alpha-azido-N-arylamides was found to proceed under an oxygen atmosphere to afford azaspirocyclohexadienones. The present transformation is carried out by a sequence of denitrogenative formation of iminyl copper species from alpha-azido-N-arylamides and their imino-cupration with an intramolecular benzene ring on the amido nitrogen followed by consecutive formation of C=O bonds. The preliminary investigation revealed that molecular oxygen is a prerequisite for achieving the present catalytic cyclization and that one of the oxygen atoms of O(2) was found to be incorporated into the cyclohexadienone moiety.