Visible-light-mediated aerobic oxidation of toluene via V2O5@CN boosting benzylic C(sp3)[sbnd]H bond activation

Abstract

Incorporating photocatalysis into benzylic C(sp3)H oxidation represents a recent advance of organic synthesis in a sustainable manner. Although photoinduced charge carriers enable the C(sp3)H bond to be activated under mild conditions, the reaction scale and activity remain hindered by the photoactivation efficiency. Herein, we present that the 1.0% V2O5@CN photocatalyst, a visible-light-active C3N4-based material, is striking active for the aerobic oxidation of benzylic C(sp3)H bonds, affording a conversion rate 11.6 times higher than that of independent CN. The enhanced activity and C(sp3)H bond photoactivation, as well as the induction period shortening and active period acceleration, are rationalized by the low-EVB hole injection from V2O5 into CN and the boosted charge separation. The durability and utility are affirmed in multiple catalytic cycles, scalable long-term reactions, and available substrate scopes. Reactive intermediate studies by EPR demonstrate the involvement of CH2Ph, O2−, and OH radicals in photoredox catalysis. The mechanism that causes the change of main product species is attributed to the formation of OH in the later reaction stage. This work indicates a unique photoactive V2O5@CN catalysis mode, opening up the efficient use of CN in scalable photocatalytic toluene oxidation.