The study of the photochemical behavior of 5-aryl-2,3-dihydropyrazine 1,4-dioxides.

For the first time, the photochemical behavior of aryl-substituted 2,3-dihydropyrazine 1,4-dioxides was investigated. A common feature of all observed photoprocesses is the conversion of nitrone moieties into an oxaziridine ring to give substituted bi- or polycyclic systems. It was shown that the direction of the reaction depends on the irradiation wavelength and the employed solvent. For instance, the use of 365 nm UV light leads to the cyclization of both nitrone moieties. In contrast, visible-light irradiation (450 nm) allows one to regiospecifically utilize an aldonitrone unit to form 7-oxa-1,4-diazabicyclo[4.1.0]hept-4-ene 4-oxide derivatives. Generally, the oxaziridine ring possesses high reactivity and can be transformed in situ by various reagents. The molecular and crystal structures of the representatives of both bicyclic systems were solved for the first time with X-ray diffraction analysis.