Patent GB-814249-A (GB)
Title: Manufacture of di-imidazole derivatives
Filed: 1955-08-26
Abstract: The invention comprises (1) di-imidazoles of the formula <FORM:0814249/IV (b)/1> or the tautomeric form <FORM:0814249/IV (b)/2> where A is an aromatic nucleus (which may be substituted, especially by sulphonic acid groups) attached by two vicinal carbon atoms, and R and R1 are H, alkyl, hydroxyalkyl or benzyl; also salts of these; and (2) the preparation of di-imidazoles of the formula <FORM:0814249/IV (b)/3> (or tautomeric form thereof) where X is H or OH and the other symbols are as above, by dehydrating a compound of the formula <FORM:0814249/IV (b)/4> (or salt thereof), and if desired treating the product with a sulphonating, alkylating, oxyalkylating or benzylating agent. The dehydration may be effected by heating the compound to 150-220 DEG  C., preferably in the presence of a high-boiling organic solvent and/or a dehydrating agent.  If concentrated sulphuric acid or oleum is used for this purpose (no heating then being required) sulphonation occurs at the same time. The starting materials (cf. Specification 813,771) can be prepared in situ by heating an o-diamine with malic or tartaric acid (or functional derivative of such acid, e.g. lower alkyl ester), if desired in the presence of a catalyst or a high-boiling organic solvent, and then further heating at a higher temperature to effect dehydration.  Alternatively an o-nitroamine can be acylated with malic or tartaric acid, the nitro group reduced and the di-imidazole formed by ring closure.  The groups R and R1 (if not already present) can be introduced by treatment with an alkyl halide, dialkyl sulphate, alkylene chlorhydrin or benzyl chloride.  The products are optical brightening agents.  In examples: (1) o-phenylene diamine is condensed with malic acid and sulphuric acid to give the sulphate of 1 : 2 - di - (21 - benzimidazyl) - ethanol, which is treated with oleum in the cold to form 1 : 2 - di - (x - sulpho - benzimidazyl - 21) - ethylene; (2) the intermediate of (1) is heated in tetrahydro-naphthalene to produce the sulphate of 1 : 2 - di - (21 - benzimidazyl) - ethylene; (3) the reaction of (1) is carried out in the absence of sulphuric acid; the hydrochloride of the product is mentioned; (4) the intermediate of (1) is dehydrated with alcoholic sodium hydroxide or by dry heating, and the product converted into its N : N1-dibenzyl, N-hydroxyethyl and N : N1-dimethyl derivatives with benzyl chloride, ethylene chlorhydrin and dimethyl sulphate respectively; (5) the intermediate of (3) is heated with zinc chloride; (6) the sulphate of 1 : 2 - di - (21 - benzimidazyl) - ethane - 1 : 2 - diol is heated alone. Substituted compounds that may be similarly dehydrated and/or sulphonated are the 6-methyl, 6-methoxy, 6-chloro, N-methyl, N-hydroxyethyl and N-benzyl derivatives.  1 : 2-Naphthylene diamine may also be used as ultimate starting material.  The products form salts with, e.g., sulphuric, hydrochloric, nitric, formic and acetic acids.ALSO:Azo dyes are made from diazonium compounds and coupling components of the formula <FORM:0814249/IV (c)/1> or their tautomeric forms <FORM:0814249/IV (c)/2> where A is an aromatic nucleus (which may be substituted, especially by sulphonic acid groups) attached by vicinal carbon atoms, and R and R1 are H, alkyl, hydroxyalkyl or benzyl. The compound 1 : 2-di-(21-benzimidazyl)-ethanone is specified as coupling in alkaline solution.  Specification 813,771, [Group IV (b)], is referred to.