Efficient synthesis and spectroscopic analysis of 8-nitro spiro C-3-annulated 2-benzazepines and their N-oxides

Nitroderivatives 9a-g have been prepared with great C-8 regioselectivity by allowing the corresponding 1,2,4,5-tetrahydrospiro[H-3-2-benzazepine-3,1'- cycloalkanes] 8a-g to react with potassium nitrate and concentrated H2SO4. The oxidative reaction of a nitrogen-carbon bond in spirobenzazepines 8 and 9 was performed with H2O2 and catalytic amounts of sodium tungstate at roo m temperature affording nitrones 10a-d in moderate to high yields. Stereoch emical assignments for all the 2-benzazepine derivatives obtained were deri ved from a full analysis of the H-1 NMR spectroscopic data and an X-ray cry stallographic analysis of 1,5-dimethyl-8-nitro-1,2,4,5-tetrahydrospiro[H-3- 2-benzazepine-3,1'-cyclohexane] 9c. These data indicate that the 2-benzazep ines 8-11 in solution present the azepine ring preferably in the chair conf ormation, with the methyl substituent at C-5 disposed equatorially.