Mechanistic study of the direct oxidative photocatalytic aerobic C[sbnd]H/C[sbnd]H coupling of azines with heteroarenes

Abstract

Experimental facts on the mechanism of the direct oxidative photocatalytic CH/CH coupling of azines with (hetero)aromatic nucleophiles, proceeding in the presence of TiO2 as a photocatalyst, have been obtained by using EPR spectroscopy and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), N-(1-hydroxy-2,2,6,6-tetramethylpiperidin-4-yl)-2-methylpropanamide (TMT-H), as spin trap reagent and spin probe, respectively. The formation of the superoxide radical anion (O2−) and N-centered radicals has been detected for the first time for the SNH transformations.