Abstract
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[3.3.1.0 3,7]nonan-4α-o1-6,6-dioxide. LiA1H 4 and LiA1D 4, 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-o1 and its 3α-deuterio analog, respectively.
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