Synthesis of stable 3,6-epidioxypyrazin-2-ones and α-oxo imides by photo-oxygenation of pyrazin-2-ones with singlet oxygen

Abstract

Irradiation of the pyrazin-2-ones (1) in methanol under oxygen gave the 3,6-epidioxypyrazin-2-ones (2), the N-alkyl-N-acyl-α-oxo amides (3), and the unusual products, N-alkyl-α-acyloxy-α-methoxy amides (4). The mechanism for the formation of these photoproducts is discussed. Furthermore, thermal or photochemical treatment of the 3,6-epidioxypyrazinones (2), which could be readily obtained by the reaction of (1) and singlet oxygen, gave the N-alkyl-N-acyl-α-oxo amides (3) and this reaction would provide a useful synthetic method for the α-oxo imides (3).