NOVEL THERMOLYTIC TRANSFORMATION OF N-BENZOYL 2-AZA 3-OXA BICYCLO(2.2.1)HEPT-5-ENE AND N-BENZOYL 2-AZA 3-OXA BICYCLO(2.2.1)-HEPTANE

Article abstract of DOI:10.1016/S0040-4020(01)92441-X

Novel thermolytic pathways were encountered in careful studies with N-benzoyl 2-aza 3-oxa bicyclo(2.2.1)heptene (1) and N-benzoyl 2-aza 3-oxa bicyclo(2.2.1)heptane (2).Compound 1 thermally fragments by four pathways, namely, (3,3)-sigmatropic shift, (4+2)-cycloreversion, N-O rupture and C-N homolysis.The (3,3)-sigmatropic shift provides a novel route to unusual, bicyclic heterocycles.Electron withdrawing aryl groupings tend to promote the (3,3)-sigmatropic shift pathway over others.The (4+2)-cycloreversion of 1 leads to nitroso carbonyl benzene and cyclopentadiene.The weak ? bonds of PhCONO undergo ready homolysis.The intermediate arising from N-O rupture leads to a cyclopentenone radical similar to that involved in the PG endoperoxide -> PGE change.This radical either combines with benzoyl radical leading to 4-dibenzoylamino cyclopentenone or is transformed to an enamide by loss of hydrogen.The N-O rupture leads to the formation of benzanilide.Nitrosocarbonyl benzene is a powerful electrophile.With cyclohexene it forms a hydroximic ester, initiated by nucleophile acceptance at the CO oxygen.In contrast, it reacts with P(OMe)3 leading to diphenylurea via nucleophile acceptance at N=O oxygen.Thermolysis of 2 proceeds largely by N-O rupture, similar to that normally observed in the PG endoperoxide -> PGE change.