Palladium-Catalyzed Intermolecular [5+2] Cycloaddition: Highly Regioselective Synthesis of Allene-Containing 2-Benzoxepines

Abstract

Palladium-catalyzed intermolecular [5+2] cycloaddition of propargylic carbonates with benzyl allenyl ethers has been developed for the synthesis of allene-containing 2-benzoxepines. The reaction proceeds by a pathway involving decarboxylative allenylpalladium formation, regioselective intermolecular insertion, and intramolecular nucleophilic attack. In this way, the sequential formation of C−C and C−O bonds results in the generation of a 2-benzoxepine skeleton in a one-pot process.