Photoredox-catalyzed regioselective allene alkoxycarbonylations for the synthesis of α-allyl-γ-lactones

A dual photoredox/hydrogen atom transfer (HAT) strategy for the radical alkoxycarbonylation of allenes is described. Alkoxycarbonyl radicals, generated by photoredox-catalyzed decarboxylation of alkyl oxalic acids, add to the proximal carbon of allene precursors with high regioselectivity to furnish α-allyl-γ-lactone products in up to 92% yield. The intermediate vinyl radicals can be trapped by a hydrogen atom or by a heteroatom using selenium and iodine transfer reagents. The alkene and vinyl moieties are readily post-functionalized to furnish more complex molecular scaffolds, highlighting the synthetic utility offered using the combination of allenes and oxalic acids as compared to their alkene and oxalate salt counterparts.