Hydroxyl-Diazomethylation of Alkenes via Photoredox Catalysis

α-Diazoesters belong to significantly important carbenoid precursors in synthetic chemistry, diazomethylation-based difunctionalization of alkenes is highly valuable but remain nontrivial. Herein, we reported a general and modular approach for the direct 1,2-hydroxyl-diazomethylation of alkenes through visible-light photoredox catalysis. This process exploits photocatalyzed strategy to convert alkenes to γ-hydroxyl-α-diazoesters using α-diazo iodonium salts as carbyne precursors, featuring wide substrate tolerance and broad late-stage diversifications. Mechanistic studies suggest that the formation of γ-carbocation-tethered α-diazoesters plays a crucial role in trapping H2O to allow for this transformation.