Diazo-Preserving Radical Cascades for the Modular Photoinduced Synthesis of Oxindoles and Pyrazolones

High Resolution Image Download MS PowerPoint Slide We report a metal-free photocatalytic strategy for the modular synthesis of diazo-containing oxindoles and pyrazolones from readily available precursors. Diazomethyl radicals are generated either via a three-component electron donor–acceptor (EDA) complex involving acrylamides or through a photoredox cycle for the activation of hydrazides, enabling C(sp 2 )–C(sp 3 ) bond formation while preserving the diazo functionality. The method tolerates a broad range of functional groups, substitution patterns, and pharmaceutically relevant motifs. Mechanistic studies, including radical trapping, UV–vis spectroscopy, light on/off experiments, and Stern–Volmer analysis, support a radical chain propagation and distinguish the EDA-driven versus photoredox pathways. The resulting diazo heterocycles undergo downstream transformations to access new chiral centers and functional motifs.