Pyrimidopteridine-Catalyzed Hydroamination of Stilbenes with Primary Amines: A Dual Photoredox and Hydrogen Atom Transfer Catalyst

The applicability of a heteroaromatic photoredox catalyst in an additive-free photo-mediated hydroamination of stilbenes is described. Initiated by the excitation of a highly potent organic pyrimidopteridine photoredox catalyst (E*­[PrPPT*/PrPPT·–] = +2.10 V vs SCE in MeCN), the photo-mediated hydroamination of stilbenes was enabled using unprotected, primary aliphatic, allylic, benzylic amines for the synthesis of various α-phenyl phenethylamine derivatives. Notably, the stereogenic center of α-chiral amines was fully preserved. Both starting materials serve as competent quenching partners. Fluorescence- and competitive fluorescence-quenching experiments as well as electron paramagnetic resonance spectroscopic analysis and density functional theory calculations allowed a plausible reaction mechanism to be deduced.