Diazo compounds of the heterocyclic series. 4. Some peculiarities of the diazo coupling of benzimidazole-2-diazonium salts with phenols and their ethers

The corresponding hydroxy (methoxy)-substituted azobenzimidazoles were obtained by diazo coupling of benzimidazole-2-diazonium salts with phenols and their complete and incomplete ethers in strongly acidic media; in the case of phenol ethers the process is complicated by dealkylation of the methoxy group in the ortho position relative to the azo bridge.See [1] for Communication 3.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 637–642, May, 1990.     

Reaction of 2-arylazobenzimidazolium quaternary salts with amines

Different behaviors of aromatic and nonaromatic amines with respect to a change in the structure of the salt and variations in the reaction conditions were revealed in a study of the reaction of 2-arylazobenzimidazolium quaternary salts with amines. Aliphatic and secondary cyclic amines react at comparable rates via pathways involving cleavage of the azo group and replacement of the hydrogen in the para position relative to the azo group. The reaction with aromatic amines proceeds primarily via the amination pathway, and a methyl group in the meta position relative to the azo group facilitates replacement of the hydrogen atom significantly.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 817–824, June, 1982.