Acid-catalyzed photoreaction of 6-chloro-1,3-dimethyluracil in frozen benzene: formation of novel cycloadducts, tetrahydropentaleno[1,2-e]pyrimidine-2,4-dione derivatives

Article abstract of DOI:10.1246/cl.1997.99

Contrasting to the photoreaction of 6-chloro-1,3-dimethyluracil in benzene at ambient temperature in the presence of trifluoroacetic acid, whereby 1,3-dimethylcyclooctapyrimidine was produced as a sole cycloadduct, the similar photoreaction in frozen benzene at -15 ～ -20°C proceeded quite differently to give three novel photocycloadducts, 7-chloro-1,3-dimethyl-4b,5,7a,8-tetrahydropentaleno[1,2-e]pyrimidine-2,4-dione, 5-chloro-1,3-dimethyl-4b,7,7a,8-tetrahydropentaleno[1,2-e]pyrimidine-2,4-dione, ando-chloro-10,12-diazapentacyclo[6.4.0.0^1,3.0^2,5.0 ^4,8]-dodecane-9,11-dione.