Photoinduced C(sp³)-H functionalization via the photocatalyst-free hydrogen atom transfer pathway

The direct functionalization of aliphatic C-H bonds represents a significant advancement in chemical synthesis, offering an efficient and sustainable strategy for the rapid assembly and late-stage modification of complex molecules. Recently, photocatalyst-free, light-promoted C(sp³)-H functionalization, which eliminates the need for expensive transition metals and photosensitizers, has been recognized as a more environmentally benign and cost-efficient approach. This mini-review highlights recent scientific advancements in the functionalization of C(sp³)-H bonds through the photocatalyst-free hydrogen atom transfer (HAT) pathway. We categorize these methodologies based on their specific photoactivation pathways, and provide a detailed discussion on the reaction conditions, substrate scope, and underlying mechanisms.