Efficient Palladium-Catalyzed Aerobic Arylative Carbocyclization of Enallenynes

Abstract

Herein, we communicate a selective and efficient protocol for oxidative arylating carbocyclization of enallenynes using O₂ as the oxidant. The key to success for this aerobic transformation is the application of a specific electron transfer mediator (ETM), a bifunctional catalyst consisting of a metal-macrocycle and quinone moieties. This catalyst significantly facilitates the reoxidation of Pd⁰ to Pd^II under atmospheric pressure of O₂ . Diverse functionalized enallenynes react with aryl boronic acids to afford the corresponding cyclic tetraenes in moderate to good yields.

Keywords: aerobic oxidation; carbocyclization; electron transfer mediator; enallenyne; palladium.