A highly efficient and selective aerobic cross-dehydrogenative-coupling reaction photocatalyzed by a platinum(II) terpyridyl complex

Abstract

Thanks to the superior redox potential of platinum(II) complex compared with that of Ru(bpy)3(2+) in the excited state, an efficient and selective visible-light-induced CDC reaction has been developed by using a catalytic amount (0.25 %) of 1. With the aid of FeSO4 (2 equiv), the corresponding amide could not be detected under visible-light irradiation (λ=450 nm), but the desired cross-coupling product was exclusively obtained under ambient air conditions. A spectroscopic study and product analysis revealed that the CDC reaction is initiated by photoinduced electron-transfer from N-phenyltetrahydroisoquinoline to the complex. An EPR (electron paramagnetic resonance) experiment provides direct evidence on the generation of superoxide radical anion (O2(-·)) rather than singlet oxygen ((1)O2) under irradiation of the reaction system, in contrast to that reported in the literature. Combined, the photoinduced electron-transfer and subsequent formation of superoxide radical anion (O2(-·)) results in a clean and facile transformation.