Alkyne Oxidation by a Vitamin B2-Based Photocatalytic System with Both H<sub>2</sub>O and O<sub>2</sub> as the Oxygen Source
Duyi Shen, Fubi Zhong, Ting Ren, Linghui Li, Zihan Li, Junzhong Yin, Peiwei Gong, Fanjun Zhang, Chengwei Lv, Mianran Chao
Abstract
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-2Sc 3+ ]* 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.