Visible Light-Mediated Copper(I)-Catalysed Aerobic Oxidation of Ynamides/Ynamines at Room Temperature: A Sustainable Approach to the Synthesis of α-Ketoimides/α-Ketoamides

A novel visible light-mediated, copper-catalysed aerobic oxidation of the C≡C bond in ynamides/ynamines at room temperature by using molecular oxygen as an oxidant is described. Overall, 23 examples were demonstrated with substrates having a wide range of functional groups. The current protocol can be readily scaled up to a preparative (1–2 g) scale with high yields (78–92%), high atom efficiency, and reaction mass efficiency. The mechanistic study shows that in-situ formation of a copper(I)-coordinated π-complex (λmax=460 nm) is most probably the key light absorbing species responsible for the visible light-induced oxidation of ynamides and ynamines. This sustainable oxidation approach allows the direct synthesis of potentially important novel α-ketoimide/α-ketoamide skeletons without the need of external oxidants (organic/inorganic oxidants) and generation of stoichiometric amounts of wastes.