Cationic palladium-catalyzed [5 + 2] annulation of 2-acylmethoxyarylboronic acids and allenoates: synthesis of 1-benzoxepine derivatives.

The 1-benzoxepine derivatives were synthesized conveniently by cationic palladium-catalyzed [5 + 2] annulation reaction of 2-acylmethoxyarylboronic acids with allenoates in high yields. This annulation involves the intramolecular nucleophilic addition to ketones without the formation of π-allylpalladium species.