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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.

Tetrafold Sonogashira reactions of tetrachloropyrazine were investigated to provide a one-step synthesis of various tetraalkynylpyrazines. The reaction conditions were thoroughly optimized using modern catalysts and ligands, and products were generally isolated in good to excellent yields. Furthermore, photophysical and electrochemical properties of selected compounds were studied and compared with those of previously reported tetraalkynylpyridines and benzenes. As a matter of fact, tetraalkynylpyrazines proved to show very promising fluorescence properties due to very high quantum yields reaching up to 0.85.