PHOTOCHEMISTRY OF 9,10-DIHYDRO-1,3,5,7-TETRAMETHYL-9-METHYLENECYLOOCTAPYRIMIDINE-2,4-DIONE:SYNTHESIS OR NOVEL RING SYSTEMS THROUGH ELECTROCYCLIC REACTIONS~1

摘要

Photolysis of 1,3,5,7,9-pentamethylcyclooctapyrimidine-2,4-dione (1a) preparec by the photoreaction of 6-chloro-1,3-dimethyluracil with mesitylene in the presence of TFA at low temperature resulted in the formation of the 9-exo-methylene derivative (2),which was further converted into a novel cyclopropa-pentalenopyrimidine (5) and a cyclobutaquinazoline (3) through [4+2]and [2+2] electrocyclic reacitions, respectively. The latter (3) was ultimately transformed into the 9,11-diazapentacyclo[6.4.0.0~(1,3).0~(2,5).0~(4,8)]dodecane-2,4-dione derivative (4).