Dimroth rearrangements, benzotriazole

Azide 367 is prepared from 4-r -butyl-2-nitroaniline in 76% yield by its diazotization followed by treatment with sodium azide. In a 1,3-dipolar cycloaddition with cyanoacetamide, azide 367 is converted to triazole 368 that without separation is directly subjected to Dimroth rearrangement to give derivative 369 in 46% yield. Reduction of the nitro group provides ortfc-phenylenediamine 371 in 91% yield <2000EJM715>. Cyclocondensation of diamine 371 with phosgene furnishes benzimidazol-2-one 370 in 39% yield, whereas its reaction with sodium nitrite in 18% HC1 leads to benzotriazole derivative 372, which is isolated in 66% yield (Scheme 59). Products 370 and 372 exhibit potassium channel activating ability <2001FA841>. 

Ring-chain equilibria of 1,2,3-triazoles and benzotriazoles with the isomeric a-diazo imines result in the well-known Dimroth rearrangement (see Section 4.01.4.1.1). 

In this section, the reactivity of the major types of aromatic 1,2,3-triazoles and benzotriazoles is considered and compared with that which would be expected on the basis of electronic theory and spectroscopic data presented in Section 4.11.3. Tautomeric equilibria and ring-chain tautomerisms are discussed in Section 4.11.4.1.2(i), Dimroth rearrangements in Section 4.11.4.1.2(iii) and acid-base considerations are discussed in the section immediately following. 

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