title: Electrocyclic rearrangement of pentamethylcyclooctapyrimidine-2,4-diones: reaction pathway into a 9,11-diazapentacyclo-[6.4.0.0(1,3).0(2,5).0(4,8)]dodecane system and a 9,11-diazapentacyclo [6.4.0.0(1,3).0(2,6).0(4,8)]dodecane system.
abstract: 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 (1b) 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 1c 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).
authors.affiliation: Faculty of Pharmaceutical Sciences, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido 061-0293, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Ohkura
authors.forename: K
authors.initials: K
authors.lastname: Nishijima
authors.forename: K
authors.initials: K
authors.lastname: Seki