Aminonitrene

A -Amino- and A-substituted amino-pyrroles readily undergo Diels-Alder additions and add to activated alkynes at room temperature. The resulting azanorbornadienes extrude A-aminonitrenes and this forms the basis of an unusual synthesis of benzene derivatives (81S753,81TL3347). It has been found that ethyl/3-phenylsulfonylpropiolate (135) is a superior dienophile to DMAD (Scheme 50). 

Aminonitrene (isodiazene) (145) is the least stable of all isomers of the elemental composition N2H2 and was isolated in an argon matrix for the first time in 1984.195 Theoreticians also gave much attention to aminonitrene (145).196 This molecule is exceptional in so far, that it is one of the few nitrenes with a singlet electronic ground state and is best described by the dipolar structure 145. ... 

Diimide has three isomers cis- and fraws-diimide as well as 1,1-diimide (aminonitrene) (Figure l)77-80. Although fraws-diimide is the only isolated and characterized diimide, cw-diimide must be formed as a reactive intermediate in the reduction system72,77. 

Schultz, Dervan, and co-workers " subsequently reported the synthesis and characterization of the five-membered ring analogue 65. As before, the oxidation of the appropriate hydrazine at 78 °C gave a clear, colored solution of the aminonitrene. This 1,1-diazene absorbs at 497 nm (in CH2CI2) and 487 nm (in 2-propanol). The IR spectrum shows a strong absorption at 1638 cm that disappears on warming to 25 °C. The isotopomer has a vibration at 1612 cm a shift of 26 cm. ... 

Both aminonitrenes 64 and 65 were also smdied by low-temperature proton nuclear magnetic resonance ( H NMR) spectroscopy. " The spectrum of the... 

Oxygen substituted nitrenes have received much less study than aminonitrenes, but there have been some noteworthy recent developments. Toscano and co-workers " studied the photochemistry of diazenium diolates. The quantum yield of photodegradation was 0.10. 

R = acyl groups. As discussed on p. 202, singlet nitrenes add stereospecifically while triplet nitrenes do not. Diphenyl sulfimide Ph2SNH converts Michael-type substrates to the corresponding aziridines.813 Aminonitrenes R2NN have been shown to add to triple bonds to... 

N- Aminopyrroles undergo Diels-Alder addition with alkynes bearing electron-withdrawing groups. Loss of N- aminonitrene from the resulting adducts yields benzenoid derivatives (Scheme 68) (81TL1767) (see also Section 3.02.2.10). 

A-Amino- and N-substituted aminopyrroles readily undergo DielsAlder reactions and add to activated alkynes at room temperature. Loss of. V-aminonitrene from the resulting adducts yields benzene derivatives (Scheme 113). 

The oxidation of 1,1-disubstituted hydrazines can be achieved by a wide range of oxidants. The oxidative removal of hydrogen formally leads to the production of aminonitrene, or 1,1-diazene, intermediates and many products of such reactions have been interpreted as being derived from aminonitrene intermediates. Indeed, several of these species, derived from sterically hindered hydrazines by oxidation with nickel peroxide or r-butyl hypochlorite, have been detected and characterized in solution at low temperature. Examples include the diazenes (14) and (15). The diazene (16) is stable enough to persist in solution at room temperature for several days. ... 

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