Oxidation of heterocyclic nitrogen yields to nitroheterocycles. [Nitrofurazans]

In the process of finding new routes to synthesize nitrofurazans the investigators compared the oxidation of a sulfilimide and a phosphine imine derived from 3-amino-4-(chlorophenyl)furazan (1). The sulfilimine, 3-(4-chlorophenyl)-4-dimethyl-sulfiliminofurazan (2), was prepared by treating 1 with dimethyl sulfide ditriflate. Oxidation of 1 with peroxytrifluoroacetic acid (ptfa) in dichloromethane gave a mixture that was chromatographed to give 3-(4-chlorophenyl)-4- nitro-furazan (5) in 11% yield and azoxy(4-chlorophenylfurazan) (6) in 32% yield. Under the same conditions, 2 gave a 96% yield of 5 with no trace of 6. Oxidation of diaminofurazan (7) with ptfa gives 3-amino-4-nitrofurazan (8), which was converted to the sulfilimine. Treatment of the sulfilimine with anhydrous ptfa in dichloromethane gave a solution that contained dimethyl sulfone according to /sup 13/C-NMR analysis, but no nitrocarbon could be detected. However, the /sup 14/N-NMR spectrum contained a very sharp singlet with a width at half-height of 19 Hz and a chemical shift almost identical to that of 5. Thus, it appears that we may have formed dinitrofurazan in solution, but we have not been able to isolate it in pure form as yet. 10 refs., 4 figs