Benzotriazoles and Higher Fused Systems

Treatment of benzimidazole with ozone and N02 results in a complex mixture of mono- and di-nitrated benzimidazoles and triazoles. However, nitration of 5-nitrobenzimidazole 1209 under such conditions leads to two major products, benzotriazoles 1210 and 1211. The mechanism of ring conversion from benzimidazole to benzotriazole is not clear (Equation 29) 2004CPB570 . 

3-Triazoles fused with larger aromatic systems can be also obtained this way. Thus, in an example given in Equation (30), 2i/-phenanthro[9,10-r/l-l,2,3-triazole 1221 is obtained in 84% yield from a reaction of 3-hydroxyphe-nanthro-l,2,4-triazine 1220 with NCS 2000H(53)203 . 

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