Visible Light Catalysis Assisted Site-Specific Functionalization of Amino Acid Derivatives by C-H Bond Activation without Oxidant: Cross-Coupling Hydrogen Evolution Reaction

Visible light catalysis assisted site-specific modification of alpha-amino acids by C-H bond functionalization without the use of any oxidant or base is described. Using Ru(bpy)(3)(PF6)(2) and Co(dmgH)(2)pyCl as a photosensitizer and a catalyst, respectively, a variety of glycine esters with beta-keto esters or indole derivatives can be quantitatively converted into the desired cross-coupling products and hydrogen (H-2) in good to excellent yields under visible light irradiation. A mechanistic study reveals that the cascade electron transfer processes from glycine ester to the photoexcited Ru(bpy)(3)(PF6)(2) and then to Co(dmgH)(2)pyCl catalyst, together with the capture of protons delivered by substrates, are crucial for the cross-coupling hydrogen evolution reaction of secondary amines in organic solvents.