Patent GB-438484-A (GB)
Title: Manufacture of hexamethine dyestuffs
IPC: C09B23/08
Filed: 1934-05-18
Abstract: Hexamethine dyes useful as intermediates for the production of unsymmetrical heptacarbocyanine dyes (cf. Specification 438,449) are preferred by condensing a quaternary ammonium salt of a heterocyclic base of the thiazole, selenazole or quinoline series containing a reactive methyl group with an equimolar proportion of a pentamethine compound of the formula <FORM:0438484/IV/1> (wherein R1 stands for an aryl residue, R2 for hydrogen, alkyl or aralkyl residue and X for an acid residue, such as chlorine or bromine, and wherein one or more hydrogen atoms of the pentamethine chain may be replaced by an alkyl group or groups), in presence of an alkaline condensing agent. Suitable alkaline condensing agents are primary, secondary or tertiary amines, or sodium ethylate and they are preferably used in amounts not exceeding the equivalent to the quantity of heterocyclic base, although in some cases the condensing agent may serve simultaneously as a solvent.  The dyes are assigned the general formula <FORM:0438484/IV/2> wherein R1 and R2 are as above, R3 and R4 stands sor hydrogen, alkyl or aryl, or, if desired, in combination stand for unsubstituted or substituted phenylene, naphthylene or other polynuclear arylene group (alkyl, aryl, alkoxy, thioalkyl, amino or substituted amino groups are mentioned as substituent radicles) and X for an acid radicle; one or more hydrogen atoms of the hexamethine chain may be replaced by alkyl groups; further when Y stands for --CH = CH-- the hexamethine chain may be attached to the heterocyclic ring in p-position to the nitrogen atom.  In examples: (1) 2-methylbenzthiazole ethiodide and 2-methylbenzselenazole ethiodide are condensed with a -phenylamido-e -phenylimido-a  : g -pentadiene hydrobromide in alcoholic piperidine; (2) 2-methylbenzselenazole ethiodide, 2-methyl-5-methoxybenzselenazole ethiodide and 2.5.6-trimethylbenzthiazole ethiodide are condensed with a -N-methylphenylamido-e  - N - methylphenylimido - a  : g  - pentadiene hydrobromide in alcohol containing triethanolamine; (3) 2-methylbenzthiazole ethiodide is condensed with a -phenylamido-e -phenylimido-g -methyl-a  : g -pentadiene hydrobromide (prepared by König's process from aniline, g -picoline and cyanogen bromide) in alcoholic piperidine. Specification 355,693 also is referred to.  The Specification as open to inspection under Sect. 91 relates to the use of quaternary ammonium salts of heterocyclic bases generally which contain a reactive methyl group and contains 3 additional examples: (4) p-toluquinaldine ethiodide is condensed with a -N-methylphenylamido-e -N-methylphenylimido-a  : p  g -pentadiene hydrobromide in presence of acetic anhydride and sodium acetate; (5) 2.5-diethyl-5-ethoxybenzthiazole ethiodide is condensed with a -N-methylphenylamido - e  - N - methylphenylimido - a  : g  - pentadiene hydrobromide in alcoholic sodium ethylate; (6) 2-methylbenzthiazole ethiodide is condensed with a -N-methylphenylamido - e  - N - methylphenylimido-a  : g -pentadiene hydrobromide in alcohol containing monomethylamine.  This subject-matter does not appear in the Specification as accepted.