Naoko Nakajima

The photochemical [4+4] cyclodimerization of 2-pyrazinone in the solid state

Abstract Irradiation of 1-methyl-5,6-diphenyl-2-pyrazinone (Ia) in the solid state gave the [4+4] anti dimer (II) in 100% yield, while (Ia) in a solution phase was inert upon irradiation.

Photooxygenation of pyrazin-2(1h)-ones

Abstract 1-Alkyl-5,6-diphenylpyra2in-2(1H)-ones (1a-b) reacted with singlet oxygen in dichloromethane to afford the stable endoperoxide (1a-b), while in methanol to afford the 1:1-adduct (3a-b) of the endoperoxide (2a-b) and methanol.

Photochemical reactions of pyrazin-2(1H)-ones

Irradiation of 1-alkyl-5,6-diarylpyrazin-2(1H)-ones (1a–c) in alcohol under oxygen gave N-alkyl-acetamide derivatives (2a–e) in 21–69% yield. The formation of acetamide derivatives (2) arises via the endoperoxide intermediates (3), initially produced by the reaction of the pyrazin-2(1H)-ones (1), which act as their own sensitizer, with singlet oxygen followed by O–O bond fission, alcohol addition, and rearrangement accompanied by the elimination of the corresponding nitrile derivative. The pyrazin-2(1 H)-ones (1a–d) rapidly reacted with singlet oxygen to afford the stable endoperoxides (3a–d). On the other hand, the pyrazin-2(1H)-ones (1a–d) were inert to the photolysis in benzene or methanol under argon.