Recent advances in cooperative N-heterocyclic carbenes and photocatalysis

Radical chemistry has played an important role in organic synthetic chemistry in the past decades. Additionally, the combination of N-heterocyclic carbene (NHC) catalysis and photocatalysis involving radical processes has emerged as a powerful strategy for the synthesis of useful molecules. Thus, it has received significant attention and underwent significant development in recent years. In this review, we summarized the recent advances in this rapidly growing area of research from the perspective of reaction mechanisms through NHC-bound ketyl radicals generated via single-electron oxidation with an excited-state photocatalyst, single-electron reduction with a reduced-state photocatalyst or energy transfer (EnT) with an excited-state photocatalyst, followed by the SET process. In addition, the catalytic mechanisms, design and application of these reaction modes are discussed in detail.