1-Aryl-and l-Alkyl-2-phthalimido-diazene-l-oxides, Diacylated Examples of TrisubstitutedTriazene-1-oxides: Formation, Properties, Stereoisomerizalion and Fragmentation')
SummaryOxidatively generated phthalimido-nitrene (1) reacts with nitrosobenzene @a), p-nitrosotoluene (Sb), o-nitrosotoluene (Sc), p-dimethylamino-nitrosobenzene (Sd), p-methoxycarbonyl-nitrosobenzene (Se), I, 1-dimethyl-1 -nitrosoethane (Sf) and nitrosocyclohexane (8g) to give the respective 1-substituted (2)-2-phthalimidodiazene-I-oxides 14a-g.The constitution of the 2-imidodiazene-1-oxides 14 is deduced from their spectroscopic properties. The UV. spectra of 14a-e are similar with those of the corresponding nitrobenzenes 18, thus supporting the concept of comparibility of the phthalimido-N group with an 0-atom and indicating that the phthalimido group is not in conjugation with the diazene-oxide function. This is in contrast to the situation in the non-acylated trisubstituted triazene-1-oxides 12, where conjugation is extended over the chain of all three N-atoms as exhibited by the UV. spectra of (2)-I13,3-triphenyl-, (2)-3,3-dimethyl-1-phenyl-, (Z)-3-methyl-1,3-diphenyl-, (2)-l-(l,l-dimethylethyl)-3,3-diphenyl-, and (Z)-1-(l,l-dimethylethyl)-3,3-dimethyltriazene-1-oxide (12a-e). These triazene-1-oxides are formed by the reaction of 1,l-disubstituted hydrazines 11 with three mol-equiv. of nitroso compounds 8 or from equimolar amounts of 11 and 8 in the presence of mercury oxide. Over 90% of 1,2-diphenyIdiazeneoxide (19, R = C6H5) are isolated by the reaction 11+3 8a. Possible mechanisms of the reaction of 11 with 8, and of the formation of 12 via triazanols D and of 19 (R=C6HS) via N-phenylhydroxylamine (20, R=C6H5) are given in Scheme 6 (in the latter case with experimental evidence). An independent synthesis of 12c confirms the constitutional assignment for 12.
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