Photocatalytic Reductive Functionalization of Aryl Alkynes via Alkyne Radical Anions

The direct reductive functionalization of alkynes under mild conditions presents a promising yet challenging avenue for accessing value-added molecules. Alkyne radical anions represent a distinct class of reactive intermediates characterized by both a charge and an unpaired electron, thus holding great potential for facilitating diverse bond formations, particularly in alkyne reductive functionalization. However, the synthetic utility of alkyne radical anions is limited, primarily due to the difficulty in their generation and the formation of highly unstable vinyl radical intermediates. In this study, we accomplished the direct generation of alkyne radical anions from aryl alkyne feedstocks via single electron transfer (SET) reduction with photogenerated CO2 radical anion (CO2 center dot-), enabling reductive hydroalkylation, arylalkenylation, and hydrocarboxylation of aryl alkynes. Our photocatalytic strategy features metal-free catalysis, mild reaction conditions, employment of a traceless reductant, good functional group compatibility, step- and atom-economy, and high regioselectivity. This study not only paves the way for leveraging the underexplored alkyne radical anions but also catalyzes the ongoing exploration of the bifunctional CO2 center dot- species in synthetic chemistry.