Palladium-catalyzed formal [6+2] annulation of allenyl benzoxazinanones with allenyl ethers and amides.

An efficient and regioselective coupling-cyclization reaction between allenyl benzoxazinanones and allenyl ethers or allenyl amides has been developed, enabling the synthesis of challenging eight-membered cycles in decent yields under mild conditions. In contrast to our prior work, the regioselectivity is reversed: the reaction takes place at the non-terminal CC bond of allenyl ethers and allenyl amides. A plausible mechanism involving intramolecular nucleophilic addition has been proposed.