The employment of readily available photocatalysts and
green oxygen
atom sources is recognized as a promising strategy to develop sustainable
catalysis for oxidation reactions. We herein reported a sacrificial
reagent-free system consisting of riboflavin tetraacetate (RFT), an
ester of natural vitamin B2 as the photocatalyst, and Sc(OTf)3 and NaCl as the cocatalysts for alkyne oxidation under blue
light or even sunlight irradiation to produce 1,2-diketone in which
the oxygen atoms were from both water and molecular oxygen, respectively.
A major Cl–/Cl• cycle was proposed to be
involved and achieved by the excited [RFT-2Sc3+]* complex
via single electron transfer for the first time, distinguished from
the OCl– active species by a two-electron process
in previous flavin–halide photo-oxidation systems.