Mono- and dicarboxylation of alkenes with oxalate catalyzed by a spiro-NHC-Ir(III) photocatalyst system

The photocatalytic mono- and dicarboxylation of alkenes using oxalate as the carboxylation agent, yielding substituted succinic acid and adipic acid, holds significant potential industrial value. Herein, we report the design and development of a novel pincer CCC-Ir(III) photocatalyst integrating a spiro-N-heterocyclic carbene (NHC) and a 1,4-diaza ligand, which can be effectively excited under blue light illumination (λabs = 488 nm). This catalyst enables highly regioselective mono- and dicarboxylation of alkenes under visible-light photocatalytic conditions. Various substituted succinic acids and adipic acids were obtained in high yields with high regioselectivities (up to 97% yield and >20:1 regioselectivity ratio). Mechanistic investigations reveal that the well-matched redox potential of the pincer CCC-Ir(III) photocatalyst (PC1) (Ep/2(IrIII*/IrII) = 0.59 V vs. SCE and Ep/2(IrIII/IrII) = −1.60 V vs. SCE) with the reaction system, along with its stable structure, are likely the critical factors contributing to the high reaction efficiency.