Photocyclization reaction of 5-styryl-1,3-dimethyl-uracil

Abstract The photolysis of a dilute acetonitrile solution of 5( Z )-styryl-1,3-dimethyluracil in the presence of oxygen gives the dehydrocylized product in 26.7% yield. Adding benzophenone to the 5( E )-styryl-1,3-dimethyluracil solution improved the yield of the photocyclization owing to the efficient E → Z photoisomerization due to benzophenone sensitization. Studies on the salt, sensitization and quenching effects on the photocyclization of the compound indicate that the photocyclization occurs from the lowest excited singlet ( 1 π, π * ) state of 5( Z )-styryl-1,3-dimethyluracil.