Visible Light-Induced Deoxygenative Amidation Protocol for Synthesis of Dipeptide and Amide

A green and sustainable visible light-mediated deoxygenative amidation protocol to generate acyl radicals from commercially available carboxylic acids was described. The cheap, commercially available and user friendly organic photoredox catalyst, rhodamine B, could be employed in the dipeptide and amide coupling reactions under metal-free conditions by visible light irradiation. This method showed excellent functional selectivity for the formation of peptide bond or amide bond without affecting other functional groups such as alcohols, amides, halogens and heterocycles. This reaction was applicable to challenging amide coupling reactions of hindered carboxylic acids with low nucleophilic amines. The operationally straightforward method enriches the efficient synthesis of various dipeptides and amides in moderate to good yields (55-89%).