Photochemistry of pyrimidin-2(1H)-ones: intermolecular hydrogen abstraction by an imino group nitrogen

Abstract

Irradiation of 1-alkyl-4,6-diarylpyrimidin-2(1H)-ones (1a–c) in the presence of hydrogen donors such as acyclic or cyclic ethers (2a–d), sulphides (2e–g), and xanthene (2h) gave the C–C bonded 1:1 adducts (3)–(16) of (1) and (2), via intermolecular hydrogen atom abstraction of the excited imino nitrogen of the starting pyrimidin-2(1H)-one (1). In contrast, irradiation of 1-aryl-4,6-dialkylpyrimidin-2(1H)-one (1d) in the presence of hydrogen donors gave, predominantly, the electrocyclization product (19) in addition to the 1:1 adducts (17)–(18).