Photochemical electrocyclization of 1,4,6-trisubstituted pyrimidin-2-ones to 2-oxo-1,3-diazabicyclo[2.2.0]hex-5-enes

Abstract

Photochemical reactions of 1,4,6-trisubstituted pyrimidin-2-ones have been examined. Irradiation of 1,4,6-trisubstituted pyrimidin-2-ones (1a–k) in benzene yielded the photochemical electrocyclization products, 3,4,6-trisubstituted 2-oxo-1,3-diazabicyclo[2.2.0]hex-5-enes (2a–k) in 14–85% yield as the sole product, while 1,6-dimethyl-4-dimethylaminopyrimidin-2-one (11) was photochemically inactive. The photoisomers (2a–k) were stable at room temperature.