Patent GB-411876-A (GB)
Title: Process for sensitizing photographic silver halide emulsions
IPC: G03C1/18
Filed: 1932-12-15
Abstract: For sensitizing photographic emulsions are employed unsymmetrical carbocyanine dyes of the formula <FORM:0411876/IV/1> wherein Y stands for sulphur, selenium, oxygen, or .CH=CH., Z for sulphur, selenium, oxygen, .CH=CH. or =C(CH3)2, V and W for hydrogen, alkyl, alkoxy, halogen, an amino or substituted amino group, or a fused-on benzene ring, R and R<1> for hydrogen or alkyl subject to the condition that R and R<1> are not both hydrogen and that R<1> is hydrogen when Z is =C(CH3)2, r and r<1> for alkyl, and X for an acid radicle such as halide, perchlorate, p-toluene-sulphonate, alkylo-sulphate or nitrate.  The production of such dyes and of intermediates therefor is analogous to known methods, the following data being given:--the production (a) of substituted selenazole bases is illustrated in Specification 394,537, (b) of bases containing in the 2-position ethyl or higher alkyl homologues is illustrated in Specification 405,309, (c) of bases containing as substituents amino or substituted amino groups is illustrated in Specification 400,951, and by (d), 2-methyl-6-aminobenzthiazole is prepared as described in Specification 313293, [Class 2 (iii)], or (e) 2-methyl-5-aminobenzthiazole is prepared by reducing the corresponding 5-nitro compound with iron and acetic acid, or (f) 2-4.6-trimethyl-7-aminobenzthiazole is prepared by converting 2.4-dimethyl-5-aminoacetanilide into a 2-aminothiazole compound according to the process of Specification 295,295, [Class 2 (iii)], saponifying this according to Specification 306,590, [Class 2 (iii)], and heating the resulting o-aminomercaptan with acetic anhydride.  In examples (1) 2-ethylbenzthiazole ethyliodide is condensed with diphenyl-formamidine and the resulting intermediate with 2-ethylbenzselenazole ethiodide to give 1.1<1>-diethyla -a <1>-dimethyl-benzthio -benzselenocarbocyanine iodide; (2) the intermediate of (1) is condensed with 2-methylbenzoxazole ethiodide, to give 1.1<1>-diethyl - a -methylbenzthio - benzoxacarbocyanine iodide; (3) the intermediate of (1) is condensed with 2-methyl-5-diethylaminobenzthiazole ethiodide to give 1.1<1>-diethyl-a -methyl - 6<1> - diethylaminobenzthiocarbocyanine perchlorate on adding sodium perchlorate; (4) the intermediate of (1) is condensed with 2 - methyl - 4.5 - benzobenzthiazole ethiodide to give 1 - ethyl - 1<1> - methyl - a  - methyl - 6<1> . 7<1> - benzobenzthiocarbocyanine iodide; (5) 2 - ethylbenzselenazole ethiodide is condensed with diphenylformamidine and the resulting intermediate with 2 - methyl - 6 - diethylaminobenzthiazole ethiodide to give 1.1<1> - diethyl - a  - methyl - 5<1> - diethylaminobenzseleno - benzthiocarbocyanine; (6) the intermediate product of (5) is condensed with 1.2.3.3.6. - pentamethylindole iodide to give 1 - ethyl - 1<1> - methyl - a  - methylbenzseleno - 3<1>.3<1>.6<1> - trimethylindocarbocyanine perchlorate on adding sodium perchlorate; (7) 1.1<1> - diethyl - a  - ethyl - 4<1>.5<1> - benzobenzthiocarbocyanine iodide is prepared by condensing the intermediate from 2 - n - propylbenzthiazole ethiodide and diphenylformamidine with 2 - methyl - 6.7 - benzobenzthiazole ethiodide.  The Specification as open to inspection under Sect. 91 relates to the use of unsymmetrical carbocyanine dyes containing two different heterocyclic residues linked together by a trimethenyl chain containing a substituent attached to at least one of its lateral carbon atoms (a .a <1>-positions), and describes the preparation of 1 - methyl - 1<1> - ethyl - a  - phenyl - benzoxa - benzthio - carbocyanine perchlorate by condensing the intermediate from 2 - methylbenzthiazole ethiodide and diphenylformamidine with 2 - benzylozazole dimethylsulphate and adding sodium chlorate.  This subject-matter does not appear in the Specification as accepted.