Patent GB-410481-A (GB)
Title: Process for sensitising photographic silver halide emulsions
IPC: G03C1/18
Filed: 1932-09-09
Abstract: Carbocyanine dyes are prepared by condensing a quaternary salt of a 2-methylbenzselenazole containing a substituent in the benzene nucleus with an ester of an alkyl, aryl, or aralkyl orthocarboxylic acid.  The dyes so obtained correspond to the formula <FORM:0410481/IV/1> wherein V stands for a substituent such as alkyl, halogen, alkoxy, or substituted amino group, B stands for alkyl, aryl, aralkyl, r for alkyl and X for an anion.  In examples (1) 5-methoxy-2-methylbenzselenazole methylsulphate is condensed with triethyl orthobenzoate in pyridine and the dye precipitated by adding potassium bromide; using instead of the orthobenzoate triethylorthophenylacetate the corresponding meso-benzyl dye is obtained; (2) 2 - methyl - 6 - acetylaminobenzselenazole diethylsulphate is condensed with triethyl orthoacetate in pyridine and the dye precipitated by adding potassium bromide; (3) 2 - methyl - 5 - methoxybenzselenazole diethyl - sulphate is condensed with triethylorthopropionate in pyridine and the dye precipitated by adding sodium perchlorate; (4) 2-methyl-6-propionylaminobenzselenazole dimethyl sulphate is condensed with triethyl orthopropionate in pyridine and the dye precipitated by adding potassium bromide; (5) 2-methyl-5-allyloxybenzselenazole ethiodide is condensed with triethyl orthoacetate and triethyl orthopropionate in pyridine, the dyes being precipitated by adding potassium iodide and sodium perchlorate respectively; (6) 2-methyl-5-phenylbenzselenazole diethyl sulphate is condensed with triethylorthoacetate and triethyl orthopropionate in pyridine, the dyes being precipitated by adding potassium iodide; (7) 2-methyl-5-acetyloxybenzselenazole is condensed with p-toluenesulphonic acid ethyl ester and the resulting salt condensed with triethyl orthopropionate in pyridine, the dye being then precipitated by adding potassium iodide.  Reference to the following dyes is also made :--1 . 1<1> - dimethyl - 6 . 6<1> - dihydroxybenzseleno - mesoethyl-carbocyanine iodide, 1.1<1>-diethyl-6 . 6<1> - dihydroxybenzseleno - mesomethyl - carbocyanine iodide and 1 . 1<1> - diethyl - 6 . 6<1> - bis-benzoyloxybenzseleno - meso - methyl - carbocyanine iodide.  2 - Methylbenzselenazoles substituted in the benzene nucleus are prepared by treating the correspondingly substituted o - aminoselenophenol in the form of its zinc salt with acetic anhydride, or by boiling the corresponding o - o<1> - diaminodiphenyldiselenide with acetic acid with addition of zinc dust; thus 5 - ethoxy2 - methylbenzselenazole may be prepared from 1 - amino - 2 - nitro - 4 - ethoxybenzene by conversion to the o . o<1> - diaminodiselenide body.  2 - methyl - 5 - allyloxybenzselenazole is prepared by saponifying a 5 - allyloxy - 2 - methylbenzselenazole by means of hydrobromic acid in a sealed tube and etherifying the 5-oxy derivative by means of allyl bromide in presence of potassium carbonate. p  The Specification as open to inspection under Sect. 91 also claims the manufacture of benzselenocarbocyanine dyes by condensing a quaternary salt of a 2-methylbenzselenazole which may or may not contain a substituent in the benzene nucleus, with an ester of an orthocarboxylic acid other than orthoformic acid, but this subject-matter does not appear in the Specification as accepted.