γ-Butyrolactone Synthesis from Allylic Alcohols Using the CO2 Radical Anion.

γ-Butyrolactone structures are commonly found in various natural products and serve as crucial building blocks in organic synthesis. Consequently, the development of methods for synthesizing γ-butyrolactones has garnered significant interest within the organic synthesis community. In this study, we present a direct and highly efficient approach for the synthesis of γ-butyrolactones from allylic alcohols. Notably, this study represents the first instance of γ-butyrolactone synthesis initiated by radical hydrocarboxylation using CO2 •-, generated from metal formates, followed by cyclization. This two-step process is achieved through the synergistic interaction of photoredox and hydrogen atom transfer (HAT) catalysis, resulting in the production of γ-butyrolactones with exceptional efficiency. Additionally, when employing α,α-diaryl allylic alcohol derivatives as substrates, the reaction involves 1,2-aryl migration, which occurs concomitantly with CO2 •- addition, leading to the formation of 4,5-substituted lactones in a good yield. The artificial force induced reaction (AFIR) method identified the preferred 1,2-aryl migration pathway along with potential byproduct pathways, in which the targeted 1,2-migration was found to be the most plausible pathway.