Patent GB-441624-A (GB)
Title: Manufacture and application of polymethine dyestuffs and intermediate products
IPC: C09B23/08
Filed: 1934-07-23
Abstract: Intermediate polymethine dyes are prepared by acylating with an acid chloride or anhydride a polymethine compound containing hydroxyl in the polymethine chain and resulting from the reaction of a primary or secondary amine with furfurol or with a vinylene homologue thereof. Such intermediates are assigned the general formula <FORM:0441624/IV/1> wherein <FORM:0441624/IV/2> represent residues of primary or secondary amines or of secondary cycloamines, R5 represents acyl, X stands for halogen or an acid residue and n stands for 0, 1 or 2.  Polymethine dyes which are used for sensitizing photographic silver halide emulsions to the infra-red region of the spectrum are prepared by reacting the above intermediates with cycloammonium salts containing a reactive methyl group, or with the corresponding methylene base in the presence of a condensing agent. The resulting dyes are assigned the formul  <FORM:0441624/IV/3> or <FORM:0441624/IV/4> wherein Y and Z stand for sulphur, selenium, oxygen, or a group -CH--CH- or <FORM:0441624/IV/5> (Y and Z may be the same or different), R1, R2, R3, R4 stand for hydrogen, alkyl, aryl, carboxyl or alkylcarboxyl, acyl or in some cases R1 and R2 together and R3 and R4 together stand for an unsubstituted or substituted phenylene, naphthylene or other polynuclear arylene group (suitable substituents being alkyl, aryl, alkoxy, thioalkyl, substituted or unsubstituted amino groups, free or esterified carboxylic or sulphonic acid groups), R5 stands for acyl, aracyl, alkyl or aryl-sulphonyl, R6 and R7 stand for alkyl or aryl, X for an acid residue and n for 0, 1 or 2.  Suitable condensing agents in the manufacture of the dyes are pyridine bases, aliphatic bases such as triethanolamine, alcohol and piperidine, alcohol and sodium acetate, acetic anhydride alone or together with sodium or potassium acetate. In examples: (1) the dye obtained from two molar proportions of monomethylaniline, one molar proportion of furfurol and one molar proportion of perchloric acid (cf. J. für prakt. Chemie 72, 559) is acetylated with acetic anhydride, or in the form of the chloride with acetylchloride in pyridine (it dyes tannin-mordanted cotton reddish-yellow); the resulting pentamethine compound is condensed with 2.3-dimethyl-6-phenylbenzthiazole - methylsulphate (prepared from p-aminodiphenyl by means of sulphur chloride according to the Herz method) and with 2 . 3 - dimethyl - 4 - chloro - 6 - phenyl benzthiazole methylsulphate (which is a byeproduct in the manufacture of the foregoing salt) to give heptamethine dyes containing an acyloxy substituent in the heptamethine chain; (2) the condensation product from furfuracrolein, 2 mols of monomethylaniline and 1 mol. of hydrogen chloride is acetylated in pyridine (it dyes tannin-mordanted cotton violet); the the resulting heptamethine compound is condensed with 2.3-dimethyl-6-phenylbenzthiazolemethylsulphate, and the corresponding heptamethine perchlorate is condensed with 2.5-dimethylbenzselenazole methylbromide (prepared from 4-methyl-2-nitraniline by conversion to 4-methyl-2-nitrophenylselenocyanide and this to the 4.4<1>-dimethyl-2.2<1>-diaminodiphenyldiselenide which is finally transformed to the selenazole by heating with acetic anhydride and zinc dust); nonamethine dyes containing an acyloxy substituent in the chain are obtained; (3) the dye obtained by reacting furfuracrolein, tetrahydroquinoline and hydrochloric acid is treated with benzoyl chloride in pyridine (it dyes tannin mordanted cotton blue); the resulting heptamethine compound is condensed with 2.3-dimethyl-6-phenylbenzthiazole methylsulphate to give a nonamethine dye having a benzoyloxy substituent in the chain; (4) the dye obtained by condensing one molar proportion of streptodivinylenefurol, 2 molar proportions or tetrahydroquinoline and one molar proportion of perchloric acid is treated with acetic anhydride in pyridine; the resulting nonamethine compound is condensed with 2.3-dimethyl-6-phenylbenzthiazole methylsulphate to give an undecamethine dye containing an acyloxy substituent in the chain; condensation with 2 - methyl - 5 . 6 - diethoxybenzthiazole diethylsulphate and quinaldine dimethylsulphate can also be effected but in these cases the reaction can proceed in two stages, first an intermediate from equimolar proportions of nonamethine compound and cyclammonium salt being formed which can then react with a further proportion of cyclammonium salt to give undecamethine dyes; (5) the dye obtained by reacting tetrahydroquinoline, furfuracrolein and hydrochloric acid is acetylated and the resulting heptamethine dye condensed with 1.2.3.3-tetramethylindolenium iodide to give a nonamethine dye containing an acyloxy substituent in the chain; the corresponding heptamethine perchlorate (prepared as above using perchloric acid in place of hydrochloric acid) is condensed with 2-methyl-5 . 6 - dimethoxybenzthiazole diethylsulphate, lepidine dimethylsulphate; and also with 2-methyl-a -naphthothiazole diethyl sulphate to give a further intermediate octamethine dye which is further condensed with a molar proportion of 2-methyl-6-ethoxybenzthiazole diethylsulphate to give an asymmetric nonamethine dye; (6) the dye from the reaction of furfural acrolein, perchloric acid and tetrahydroquinoline is acylated with butyric anhydride and the resulting heptamethine dye is condensed with 2-methylbenzthiazole. For sensitizing silver halide emulsions the dyes are incorporated in amounts of 0,5--1,5 milligrams per kilo emulsion and may be added as alcoholic solutions prior to the emulsion being cast, or the finished photographic material may be bathed in a dilute alcoholic solution of the dye.  Sensitizing data for the products of the examples is given.  The Specification as open to inspection under Sect. 91 comprises also the manufacture of dye intermediates of the formula given above wherein r5 stands for alkyl by alkylating the corresponding free hydroxy bodies and the manufacture of dyes derived therefrom by the process specified above; the use of such polymethine dyes containing an alkoxy substituent in the polymethine chain in sensitizing photographic silver halide emulsions is also claimed.  This subject-matter does not appear in the Specification as accepted.