Herein we report the photo‐ and electrochemical characterization of pyrimidopteridine N‐oxide‐based heterocycles. The potential of their application as organic photoredox catalysts is showcased in the photomediated contra‐thermodynamic E→Z isomerization of cinnamic acid derivatives and oxidative cyclization of 2‐phenyl benzoic acid to benzocoumarin using molecular oxygen as a mild oxidant. Furthermore, unprecedented intermolecular non‐covalent n–π‐hole interactions in solid state are discussed based on crystallographic and theoretical data.

This review summarizes the utilization of heteroarene N‐oxides as oxidant in organic reactions. The specific focus lies on reactions in which pyridine N‐oxides are used as oxygen source in an oxygen atom transfer fashion. The scope comprises the hydroxylation of aliphatic and aromatic C–H bonds, epoxidation as well as oxygenations of alkenes and alkynes. The latter have been extensively reviewed elsewhere and are merely discussed in a conceptual manner.

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.

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