Acid-catalyzed photoreaction of 6-chloro-1,3-dimethyluracil and mesitylene: formation of photocycloadducts and their characterization.

In contrast to the previously reported short time required (1 h) for photolysis of 6-chloro-1,3-dimethyluracil (6-CIDMU) and mesitylene, in the presence of TFA, resulting in two major products: 1,3,6,8,10-pentamethylcyclooctapyrimidine derivative (1d), and diazapentacyclo[6.4.0.0(1,3).0(2,5).0(4,8)]dodecane (2c), prolonged irradiation (18h) of this same mixture yields novel pentalenopyrimidine derivatives, including diazapentacyclo[6.4.0.0(1,3).0(2,6).0(4,8)]dodecane (3c).