Sulfonylnitrenes

In contrast to the acyl- and sulfonylnitrenes described in this section, arylnitrenes produced thermally or photolytically from aryl azides, including those bearing strongly electron-withdrawing substituents (e.g., CN, N02, CF3), fail to promote ring expansion of arenes to 1H-azepines, although intermolecular substitution of electron-rich substrates, e.g. mesitylene and A.TV-dimethylaniline, have been noted.167... 

Sulfonyl nitrenes react with benzene to produce appreciable yields of aromatic substitution products. The nitrene thermally generated in benzene from 229 gives a monosubstitution product. When the reaction is carried out in mesitylene as a solvent, the two sulfonylnitrenes react with mesitylene to afford 230 (equation 140)135. 

Similar results were reported independently by Shingaki and coworkers for the S, S-dimethyl-Af-ethoxycarbonyl sulfimide analogs. The photolysis of the higher valent sulfoximide derivatives, ArS02N=S(0)Me2, had earlier been reported by Abramovitch and Takaya ° not to yield the expected sulfonylnitrene but instead to give products arising... 

Sulfonylnitrenes are formed by thermal decomposition of sulfonyl azides. Insertion reactions occur with saturated hydrocarbons.255 With aromatic compounds the main products are formally insertion products, but they are believed to be formed through addition intermediates. 

For arylnitrenes only qualitative treatments have been carried out by Reiser et al. 30>. It was concluded that the ground state of arylnitrenes is also a triplet as expected from the experimental results. No quantum mechanical calculations have been reported for sulfonylnitrenes, but ESR-evidence indicates a triplet ground state also for these intermediates 47> (see below). 

With sulfonylnitrenes, additions to double bonds are very rare. The reason is that addition of the sulfonylazide to the double bond normally is much faster than azide decomposition. Another explanation is double-bond participation in the nitrogen elimination where no free nitrene is involved. 

Sulfonylnitrenes also undergo intramolecular C—insertion to give six-membered sultams. In the series of sulfonyl azides (16 n = 0, 1), the sultams were formed in low yield no five-membered sultams were observed. 

The thermolysis of o-azidosulfonyl-f-anilines resulted in nitrene formation and trapping of the nitrene by the adjacent amino nitrogen to give a zwitterionic thiadiazole dioxide 108 from the dimethyl- or 6-membered heterocyclic ring precursor. The ring-opened/dealkylated derivative 109 was formed from other dialkyl or ring systems (Scheme 36) [74 JCS(P1)2451]. The pyrrolidino azide was unique in giving no thiadiazole, but rather products derived from a sulfonylnitrene precursor, perhaps in... 

Abramovitch and co-workers,122 investigating the chemistry of aryl-nitrenes and sulfonylnitrenes, thermolyzed biarylsulfonyl azides (136) which at 120°C produced 6H-dibenzo[c,e] [ 1,2]thiazine 5,5-dioxide (138) (80%) via the proposed intermediate 137 (Eq. 34). N-Alkylation of 138 with... 

Sulfonylnitrene addition to amine nitrogen (Eq. 133)463 and insertion into aromatic C—H bonds have also been observed (Eqs. 134 and 135)465... 

Further possible applications of the rigidity of sulfonylnitrenes to the synthesis of strange compounds are illustrated by the preparation of the bridged ferrocene 408 (Eq. 140).471 This compound, which may be regarded as a heterocyclic molecule, is formed by photolysis in benzene, whereas thermolysis in the same solvent gives intermolecular insertion products... 

More general reviews on sulfonylnitrenes, including intermolec-ular reactions, are available. ... 

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