Patent GB-600696-A (GB)
Title: Manufacture of imidazole compounds
Filed: 1945-11-09
Abstract: a  : b -Di-(benzimidazyl-2)-ethylenes are manufactured by the action of a dehydrogenating agent at a raised temperature on a  : b -di-(benzimidazyl-2)-ethane or its substitution products (e.g. those which are alkylated or aralkylated in the benzene nucleus or on the imino nitrogen atom or which are substituted in the benzene nucleus by halogen atoms or nitro, methoxy or sulpho groups, including asymmetrically substituted derivatives), or on a salt of any of these compounds.  As dehydrogenating agents may be employed mild oxidizing agents such as compounds of divalent mercury (e.g. mercuric acetate or mercuric oxide), potassium permanganate, pyrolusite, copper oxide or sulphate, hydrogen peroxide, selenium dioxide, platinum oxide, ferric salts (e.g. ferric sulphate, ferrichloride or potassium ferricyanide) or organic compounds having oxidizing action, such as nitro-compounds (e.g. nitrobenzene), also elementary selenium and sulphur, and dehydrogenation catalysts (e.g. finely-divided nickel, copper, platinum or palladium), as such or supported on a carrier. The process may be carried out at 80-300 DEG  C., preferably in  the presence of a solvent.  The products may be used for optical bleaching, especially of cellulose fibres.  In examples: (1) a  : b -di-(benzimidazyl-2)-ethane is heated with mercuric acetate in glacial acetic acid; the following are similarly treated: (2) a  : b - di - (N - benzyl - benzimidazyl-2)-ethane; (3) a  : b -di-(6-nitro-and 6 - methoxy - benzimidazyl - 2) - ethane; (4) a  : b - di - (6 - chlorobenzimidazyl - 2) - ethane and a -(benzimidazyl-2)-b -(6-chlorobenzimidazyl-2)-ethane, and (5) a  : b - di - (6 - isopropylbenzimidazyl - 2) - ethane dihydrochloride; (6) a  : b -di-(benzimidazyl-2)-ethane sulphate is heated in an autoclave with an aqueous solution of ferric chloride and sulphuric acid; the following are similarly treated: (7) a  : b  - di - (6 - methyl - benzimidazyl-2)-ethane and N : N1-dimethyl-a  : b  - di - (benzimidazyl - 2) - ethane, and (8) a  : b -di-(6-nitrobenzimidazyl-2)-ethane; (9) a  : b -di-(benzimidazyl-2)-ethane is dissolved in a melt of 2-methylbenzimidazole and heated with a nickel catalyst with exclusion of air; (10) a  : b -di-(benzimidazyl-2)-ethane is sulphonated and the resulting disulphonic acid is treated with excess of caustic soda solution and heated with potassium ferricyanide; (11) a  : b -di-(benzimidazyl-2)-ethane sulphate or a  : b -di-(6-methylbenzimidazyl-2)-ethane is heated in an autoclave with an aqueous solution of ferric sulphate and sulphuric acid.  a  : b -Di-(benzimidazyl-2)-ethanes (other than those which are asymmetrically substituted) are obtainable in the form of their salts by heating an o-phenylene diamine, in which one amino group is primary and the other primary or secondary, with succinic acid or a functional derivative (e.g. the anhydride or an ester) thereof in the presence of an acqueous mineral acid (e.g. 40-50 per cent sulphuric acid, or hydrochloric acid of 20 per cent strength or stronger), if necessary under pressure, until the content of dibenzimidazyl compound no longer increases, and, if desired, alkylating or aralkylating the product, e.g. by means of an alkyl or aralkyl halide, advantageously with the addition of an acid-binding agent, or a dialkyl sulphate.  Examples are given of the treatment of o-phenylenediamine and of 1-nitro-3 : 4-diaminobenzene with succinic acid and aqueous sulphuric acid to yield a  : b -di-(benzimidazyl-2)-ethane and its 6 : 61-dinitro derivative, and of 1-methyl-3 : 4-diaminobenzene with succinic acid and aqueous hydrochloric acid to yield a  : b -di-(6-methylbenzimidazyl-2)-ethane, and of the methylation of a  : b -di-(benzimidazyl-2)-ethane with dimethyl sulphate. Reference is also made to the preparation of a  : b -di-(6-methoxy-, 6-chloro- and 6-isopropyl-benzimidazyl-2)-ethane in an analogous manner to that of the 6-methyl compounds, and to the benzylation of a  : b -di-(benzimidazyl-2)-ethane with benzyl chloride.  a -(Benzimidazyl-2)-b -(6-chlorobenzimidazyl-2)-ethane is obtainable by refluxing b -(benzimidazyl-2)-propionic acid with 1-chloro-3 : 4-diaminobenzene in 15 per cent hydrochloric acid.ALSO:a  : b -Di-(benzimidazyl-2)-ethylenes, which may be alkylated or aralkylated in the benzene nucleus or on the imino nitrogen atom or substituted in the benzene nucleus, e.g. by halogen atoms or nitro, methoxy or sulpho groups, including asymmetrically substituted derivatives, may be used for optical bleaching, especially of cellulose fibres.