FORMATION OF TETRACYCLIC OXAZOLIDINONES FROM CYCLOADDUCTS OF BENZYLIDENE KETONES WITH 4-PHENYL-4,5-DIHYDRO-3H-1,2,4-TRIAZOLE-3,5-DIONE (PTAD) BY BASE-PROMOTED BACKBONE PARTICIPATION AND REARRANGEMENT

Alcoholysis and aminolysis of urazoles 4a-j prepared by the reactions of benzylidene ketones with 4-phenyl -4,5-dihydro-3H-1,2,4-triazole-3, 5-dione (PTAD) afforded tricyclic oxazolidinone derivatives 5a-o in mo derate yields (16-77%). The structure of compound 5b was confirmed by a single-crystal X-ray analysis. The reaction proceeded via opening of the urazole ring by initial Michael addition of nucleophiles (solvent s) to the enone substructure, followed by participation of the carbony l group and final skeletal rearrangements.