Visible-Light-Mediated S-H Bond Insertion Reactions of Diazoalkanes with Cysteine Residues in Batch and Flow

We describe the application of S-H bond insertion reactions of aryl diazoacetates with cysteine residues that enabled metal-free, S-H functionalization under visible-light conditions. Moreover, this process could be intensified by a continuous-flow photomicroreactor on the acceleration of the reaction (6.5 min residence time). The batch and flow protocols described were applied to obtain a wide range of functionalized cysteine derivatives and cysteine-containing dipeptides, thus providing a straightforward and general platform for their functionalizations in mild conditions.