Visible-Light-Catalyzed Regioselective Arylcarboxylation of Allenes with CO₂

A visible-light-catalyzed arylcarboxylation of allenes with CO(2 )was developed using [Ir(ppy)(2)(dtbbpy)]PF6 (ppy = 2-phenylpyridine;dtbbpy = 4,4 '-di-tert-butyl-2,2 '-bipyridine) as a photocatalyst to synthesis beta-aryl beta,gamma-unsaturated carboxylic acids. This multicomponent protocol proceeds in an atom-economical way with exclusive regioselectivity. Preliminary mechanistic experiments suggested that allylic carbanion species are the key intermediates.