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

A CuBr2-catalyzed cascade reaction of amidines with exocyclic α,β-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.