Photoenzymatic Redox-Neutral Radical Hydrosulfonylation Initiated by FMN

The photoinduced unnatural reactions catalyzed by flavin-dependent enzymes usually proceed through reduction pathways, which required the use of electron-sacrificial reagents. Herein, we developed a photoenzymatic redox-neutral radical hydrosulfonylation induced by oxidated flavin (FMN) with sulfinates or sulfonyl hydrazines as radical precursors. The reaction involved the excited FMN acquiring an electron from the substrate, and the resulting sulfuryl radical was captured by an alkene. It is then stereoselectively quenched by flavin semiquinone (FMNsq) through hydrogen atom transfer. This study circumvents the need for NADPH recycling systems and expands the potential reaction patterns in photobiocatalysis.