2- Azido-3-methylquinoxaline 1,4-dioxide

Azido-3-methylquinoxaline 1,4-dioxide (293) underwent thermolytic ring contraction with loss of N2 to give a separable mixture of 2-methyl-3//-benzimidazole-2-carbonitrile 1,3-dioxide (294) and its rearrangement product, 3-methyl-3//-2,l,4-benzoxadiazine-3-carbonitrile 4-oxide (295) (PhH, reflux, 10 min 46% and 41%, respectively) the latter product (295) was also obtained from the benzimidazole (294) (PhH, reflux, 30 min 76%) or from the quinoxaline (293) (PhMe, 90°C, 30 min 94%). ... 

The ring contraction of 2-azido-3-methylquinoxaline 1,4-dioxide (1) to 2 is believed to proceed by an assisted non-nitrene reaction because it proceeds in solution below 100 °C. If the reaction is conducted in toluene at 90 C, however, only compound 3 is formed in 94% yield. ... 

The thermal decomposition of 2-azido-3-methylquinoxaline 1,4-dioxide appears to be the only route so far to the 2,1,4-benzoxadiazine system (see Section 6.15.7). 

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