Palladium‐Catalyzed [6+2] Double Allene Annulation for Benzazocines Synthesis

Abstract

An efficient double allene protocol for the formation of benzazocines has been developed. The reaction constitutes a highly regioselective palladium‐catalyzed formal [6+2] annulation of allenyl benzoxazinanones with terminal allenes forming the challenging 8‐membered cycles. Decent yields and excellent regioselectivity have been observed under mild conditions with a remarkable Z‐stereoselectivity for the exo‐cyclic C=C bonds. The synthetic potentials of benzazocine products have been demonstrated.