Photochemical rearomatization and dearomatization of tricarbonyl(η5-cyclohexadienyl)manganese complexes

Photoirradiation of the tricarbonyl(eta(5)-cyclohexadienyl)manganese complexes 2 in dichloromethane or cyclohexane leads to the formation of the rearomatization products 3 in high yield, while photoirradiation of 2 in acetonitrile or dimethylformamide results in 3 and deaxomatization products 5 and 6 with the ratio 1(5 + 6) of ca. 1:1. In the presence of acetic acid the photochemical reaction of 2 both in dichloromethane and in acetonitrile exclusively yields 5 and 6. The photochemical reaction of 2 might be of significant utility in the synthesis of functionalized arenes and substituted cyclohexadienes.