SYNTHESIS, STRUCTURE, AND REDUCTIVE REARRANGEMENT OF A NOVEL TRICYCLIC ISOXAZOLIDINE

Article abstract of DOI:10.1016/S0040-4020(01)82047-0

N-oxidation of 2-methyl-3β-phenyl-2,3α,3aβ,6aβ-tetrahydrothieno<2,3-d>isoxazole-4,4-dioxide (1) gave a nitrone (2) which underwent an intramolecular 1,3-dipolar cycloaddition yielding a tricyclic isoxazolidine (4).A single-crystal X-ray analysis unequivocally established the structure of 4 as 9β-phenyl-2-oxa-6-thia-1-azatricyclo<3.3.1.O^3,7>nonan-4α-ol-6,6-dioxide.LiAlH4 and LiAlD4 reduced 4 exhaustively and rearranged it profoundly to isotopomers 5 and 6, respectively; a novel Grob fragmentation may have mediated the rearrangement.Inter alia, measurements of 13C-13C coupling constants and of m/z ratios of fragment ions yielded the complete structures of 5 and 6.They are 5β-phenyl-8-thia-6-azabicyclo<3.3.1>octan-2α-ol and its 3α-deuterio analog, respectively.