Photocatalytic 1,2-Dicarboxylation of Unactivated Alkynes with CO₂

The carboxylation of widely available raw materials with CO₂ represents a highly desirable transformation in synthetic chemistry, enabling the streamlined synthesis of valuable carboxylic acids. While the photocatalytic carboxylation of activated unsaturated compounds with CO₂ has emerged as a powerful strategy for accessing diverse carboxylated products, the direct carboxylation of unactivated alkynes with CO₂ remains a formidable challenge due to the intrinsic inertness of both aliphatic alkynes and CO₂. Herein, we report the first visible-light photocatalytic 1,2-dicarboxylation of unactivated alkynes with CO₂, providing a versatile platform for synthesizing structurally diverse succinic acid derivatives. This method exhibits good functional group tolerance and high chemoselectivity under mild reaction conditions. Mechanistic investigations indicated that the in situ generated carbon dioxide radical anion (CO₂^•-) might initiate the first hydrocarboxylation of unactivated alkynes to deliver a key acrylate intermediate, which could undergo a second hydrocarboxylation process to selectively yield succinic acid derivatives. The synthetic utility of this protocol is further demonstrated by constructing bioactive molecules and CO₂-based polyesters.