Catalytic Asymmetric Oxidative γ-Coupling of α, β-Unsaturated Aldehydes with Air as the Terminal Oxidant

A novel concept for catalytic asymmetric coupling reactions is presented. Merging organocatalysis with single-electron oxidation by using a catalytic amount of a copper(II) salt and air as the terminal oxidant, we have developed a highly stereoselective carbon-carbon oxidative coupling reaction of alpha, beta-unsaturated aldehydes. The concept relies on the generation of a dienamine intermediate, which is oxidized to an open-shell activated species that undergoes highly selective gamma-homo- and gamma-heterocoupling reactions. In the majority of examples presented, only a single stereoisomer was formed.