Azidoquinoxalines ring contraction

Habib and co-workers observed the rearrangement of 2-quin-oxalinone 4-oxides (219) on treatment with acetic anhydride to 1,3-diacetyl- or l-acetyl-3-acyl-2-benzimidazolones (220).219 Recently, the ring contraction of 2-azidoquinoxaline 1-oxide to 2-cyano-l-hydroxy-benzimidazole has been reported.220... 

Azidoquinoxaline undergoes ring contraction to l-hydroxybenzimidazole-2-carbonitrile." On photolysis in methanol, 2,3-disubstituted quinoxaline 1,4-oxides undergo rearrangement to 1,3-disubstituted benzimidazolones. -" ... 

The ring contractions of 2-azidopyridine N-oxides (328) to 1-hydroxy-pyrroles,371 and of 2-azidoquinoxaline 1,4-dioxides (329)372 (Scheme 67) are also believed to be assisted nonnitrene reactions, as symbolized in formula 328, because they generally take place in solution below 100°C. 

Eighth example A further case of ring contraction has been reported on the thermolysis of 2-azidoquinoxaline 1-oxide 32 when 2-cyano-l-hydroxybenzimidazole 33 is formed (Scheme 6.12) (Abramovitch and Cue 1973). 

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