Aerobic CuBr2-Catalyzed Oxidative Coupling Reaction of Amidines with Exocyclic alpha,beta-Unsaturated Cycloketones for the Synthesis of Spiroimidazolines

A CuBr2-catalyzed cascade reaction of amidines with exocyclic alpha,beta-unsaturated cycloketones was developed, affording a large variety of spiroimidazolines in moderate to excellent yields. The reaction process involved the Michael addition and copper(II)catalyzed aerobic oxidative coupling, in which O2 from air acted as the oxidant and H2O was the sole byproduct.