Molecular oxygen-enabled photocatalyzed oxygenative coupling via C-H functionalization: advances and mechanistic insights.

Visible-light photoredox catalysis has emerged as a powerful platform for the activation and functionalization of inherently inert C-H bonds, enabling synthetically valuable transformations under mild, sustainable, and operationally simple conditions. Among the oxidants employed in these processes, molecular oxygen holds particular significance owing to its abundance, low cost, and dual function as both a terminal oxidant and an oxygen atom source. This perspective provides a concise yet comprehensive overview of recent advancements in oxygen-enabled photocatalytic C-H functionalization, with a focus on oxygenative C-C, C-N, C-S and C-O coupling reactions. Developments in transition metal-catalyzed and metal-free photoredox systems are critically discussed. Mechanistic insights into reactive oxygen species generation, and radical intermediacy are highlighted to elucidate the underlying principles governing these transformations. Collectively, the advances summarized herein underscore the growing impact of O2 driven photoredox catalysis in delivering efficient, atom-economic, and environmentally benign routes for the construction of diverse molecular architectures, thereby reinforcing its importance in contemporary organic synthesis.