A visible light-induced deoxygenative amidation protocol for the synthesis of dipeptides and amides†

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