, Volume 28, Issue 1, pp 58-63

Heterocyclic diazo compounds. 5. Reaction of benzimidazole-2-diazonium salts with naphthols and their ethers

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The principal pathways for the reaction of benzimidazole-2-diazonium ion salts with naphthols and their methyl ethers in a mixture of phosphoric acid annd acetic acid have been elucidated. In concentrated acidic media, in addition to substitution at the 4-position in naphthol and its ether, azo coupling at the 8-positin is also possible. It has been found that a 2-methoxy group in naphtylazobenzimidazole exhibits anomalously high reactivity with respect to hydrolytic cleavage, which explains the observed ease of dealkylation of the azo compound during the course of the azo coupling sequence.