Patent GB-432969-A (GB)
Title: Process for sensitising photographic silver halide emulsions and manufacture of sensitising dyes therefor
IPC: G03C1/12
Filed: 1934-02-07
Abstract: Photographic silver halide emulsions are sensitized by incorporating therein a dye of the cyanine, pseudocyanine, isocyanine, carbocyanine, or styryl series containing an unsubstituted or substituted b -b <1>-naphthoxazole nucleus. The dyes are derived from a quaternary ammonium salt of 2-methyl-b .b <1>-naphthoxazole or a substitution product thereof, reference being made to alkyl, aryl, unsubstituted and substituted amino and halogen as suitable substituents; thus pseudocyanine and cyanine dyes are prepared by condensing such a salt with a quaternary ammonium salt of a 2-iodo derivative of a quinoline base or with a derivative of a quinoline or other heterocyclic base having in the 2-position a bivalent polyatomic grouping of which the atom linked to the 2-position is different from carbon, such as the group = <FORM:0432969/IV/1> (cf. Specification 423,792); isocyanine dyes are prepared by condensing such a salt with a quaternary ammonium salt of quinoline or of a substitution product thereof in presence of an alkali alcoholate; styryl dyes are prepared by condensing such a salt with a p-dialkylaminobenzaldehyde or a substitution product thereof; carbocyanine dyes are prepared by condensing such a salt with a trialkyl ester of an orthocarboxylic acid or with an alkyl ester of a thioimidic acid (in this latter case unsymmetrical carbocyanines can also be obtained by reacting the specified salt with the thioimidic acid ester and with a quaternary ammonium salt of another hetero-cyclic base having a reactive methyl group according to the process of Specification 412,309).  The following preparations are described in examples: (1) 2-methyl-b -b <1>-naphthoxazole dimethylsulphate is condensed with triethyl orthoformate, triethylorthoacetate, triethylorthopropionate in pyridine, in each case the dyes being precipitated as the bromides by adding potassium bromide; (2) 2-methyl-b -b <1>-naphthoxazole dimethylsulphate is condensed with N-ethyltoluthioquinolone ethiodide in pyridine in presence of piperidine to give 1.6<1> - dimethyl - 1<1> - ethyl - b .b <1> - naphthoxo-pseudocyanine iodide; (3) 2-methyl-b .b <1>-naphthoxazole dimethylsulphate is condensed with p-toluquinoline ethiodide in alcohol containing sodium alcoholate to give 1.6<1>-dimethyl-1<1>-ethyl - b .b <1> - naphthoxoisocyanine iodide; (4) 2-methyl-b .b <1>-naphthoxazole dimethylsulphate is condensed with p-dimethylaminobenzaldehyde in pyridine and in presence of piperidine.  Samples have been furnished under Sect. 2 (5) of dyes prepared as follows: (a) 2-methyl-b .b <1>-naphthoxazole dimethylsulphate is condensed with ethylisothioacetanilide and the dye precipitated out by adding potassium iodide; (b) 2-methyl-b .b <1>-naphthoxazole dimethylsulphate is condensed with N - methylthiothiazolone ethiodide in pyridine and in presence of piperidine.  2-Methyl-b -b -naphthoxazoles are prepared by splitting off water from 2 - acetylamino - 3 - naphthol and substitution products thereof.  The quaternary ammonium salts thereof are formed in the usual manner.  In an example, 2-methyl-b .b -naphthoxazole is prepared by heating 2-acetylamino-3-naphthol to about 180 DEG  C.