Patent GB-937620-A (GB)
Title: ªá,ªâ-di[substituted-imidazyl-(2)]-ethane sulphonic acid compounds and the preparation of ªá,ªâ-di-[substituted imidazyl-(2)]-ethylenes therefrom
IPC: C07D471/04
Filed: 1960-11-28
Abstract: The invention comprises a ,b -di[imidazyl-(2)]-ethane-sulphonic acids of the general formula: <FORM:0937620/IV(a)/1> and the salts thereof, wherein A and A1 are the same or different unsubstituted or substituted aromatic or heterocyclic rings or condensed systems of such rings in which two vicinal carbon atoms are linked to the two imidazole nitrogen atoms, and R and R1, which may be the same or different, are hydrogen atoms or alkyl, hydroxyalkyl or aralkyl radicals, and their conversion into ethylenic compounds of the general formula: <FORM:0937620/IV(a)/2> in which A, A1, R and R1 have the same meaning as above, by heating said sulphonic acid or salt thereof, preferably above 80 DEG C., in the presence of an acid-binding agent.  The latter may be an alkali metal hydroxide, either fused or in solution, an alkali metal acetate, carbonate or phosphate, or an organic base. The sulpho-compounds may be prepared by condensing 1 mol of sulphosuccinic acid, or a functional derivative such as its carboxylic acid ester, with 2 mols of the same or different aromatic or heterocyclic o-diamines in which one amino group is primary, and the other primary or secondary.  When different o-diamines are used the reaction is preferably carried out in two stages using each o-diamine separately.  The intermediate b -[imididazyl-(2)-]-sulphopropionic acid which is formed may be isolated if desired; thus, in Example 6 the preparation is described of the intermediate having the formula: <FORM:0937620/IV(a)/3> in which one of the substituents X is a sulphonic acid group, the other being a hydrogen atom.  o-Nitroamines containing a primary or secondary amino group may be used instead of o-diamines in the preparation of sulpho-compounds; after condensation with sulphosuccinic acid or a functional derivative, imidazole ring closure can be effected after the nitro group has been reduced to an amino group.  Hydrogen atoms linked to the imidazole nitrogen atoms in the a ,b -di[imidazyl-(2)]-ethanesulphonic acids can be replaced by alkyl or aralkyl groups by usual means.  The following are examples of the aromatic o-diamines which can be used for the preparation of the sulpho-compounds o-phenylenediamine, 1,2-diamino-4-isopropylbenzene, 1,2-diamino-4-chlorobenzene, 1,2-diamino-4-nitro-benzene, 3,4-diaminobenzoic acid, 3,4-diaminobenzene-sulphonamide, 1-amino-2-(b -hydroxyethylamino)-benzene, 1-amino-2-methylamino-5-methylsulphonylbenzene, 3,4,31,41-tetra-aminodiphenyl, 1,2-diamino-5-naphthol-7-sulphonic acid and 1,2-diaminoanthraquinone.  Several other examples are also given. Examples of heterocyclic o-diamines which may be used include: 2,3-diaminopyridine, 7,8-diaminoquinoline, 2,3-diamino-quinoxaline, 4,5-diaminouracil, 1,3-dimethyl-4,5-diaminouracil and 2-phenyl-5,6-diaminobenzotriazole.  Examples are given for the preparation of the following ethylenic compounds (and their related sulpho intermediates): a ,b -di-[benzimidazyl-(2)]-ethylene, a ,b -di-[6-methyl-benzimidazyl-(2)]-ethylene, N-monomethyl-a ,b -di-[benzimidazyl-(2)]-ethylene, a ,b -di-[N-methyl-benzimidazyl-(2)]-ethylene, a ,b -di-[7-methyl-benzimidazyl-(2)]-ethylene, a -[benzimidazyl-(2)]-b -[7-methylbenzimidazyl-(2)]-ethylene, a ,b -di-[21,31-naphthimidazyl-(2)]-ethylene and N-mono-(b -hydroxyethyl)-a ,b -di-[benzimidazyl-(2)]-ethylene. The ethylenic compounds are useful as optical brightening agents, and as intermediates for the manufacture of dyestuffs.