Visible-light-initiated Catalyst-free Oxidative Cleavage of Triaryl-Substituted Alkenes C=C Bonds under Ambient Conditions

The catalyst-free oxidative cleavage of (Z)-triaryl-substituted alkenes bearing pyridyl motif with ambient air under irradiation of blue LED at room temperature has been developed. The reaction was facile and scalable, proceeding with good functional group tolerance and thus affording pharmaceutically useful 2-acyl pyridines. The electron paramagnetic resonance (EPR) studies, together with the control experiments showed that the singlet oxygen (1O2) and superoxide anion (O2•−) are the reactive oxidants. The 1O2 generation mechanism correlated well with the photophysical properties of the substrate (Z)-triaryl-substituted alkenes, the excited state of which proved to be served as the triplet senstizer for generation of the 1O2.