Electrocyclic Rearrangement of Pentamethylcyclooctapyrimidine-2,4-diones: Reaction Pathway into a 9,11-Diazapentacyclo-[6.4.0.01,3.02,5.04,8]dodecane System and a 9,11-Diazapentacyclo [6.4.0.01,3.02,6.04,8]dodecane System†¶
摘要:
Photolysis of 6-chloro-1,3-dimethyluracil and mesitylene in the presence of trifluoroacetic acid (TFA) at low temperature gave 1,3,5,7,9- and 1,3,6,8,10-pentamethylcyclooctapyrimidine-2,4-diones (1b, 1c). Sequential photoreaction of the former (lb) resulted in the formation of 9,11-diazapentacyclo[6.4.0.0(1,3).0(2,5).0(4,8)]dodecane-2,4-dione (2b) by way of 9-exo-methylene derivative (7b) and cyclobutaquinazoline (8b). On the other hand, UV-irradiation of lc led to the bond shift isomer (5c) whose photolysis in the presence of TFA gave rise to the formation of the [6.4.0.0(1,3).0(2,6).0(4,8)]dodecane isomer (3c).