Patent GB-427887-A (GB)
Title: Process for sensitizing photographic silver halide emulsions
IPC: G03C1/12
Filed: 1933-09-25
Abstract: Photographic silver halide emulsions are sensitized by incorporating therein a cyanine, isocyanine, pseudocyanine, carbocyanine (including penta- and heptacarbocyanine) or styryl dye derived from a tetrahydronaphthothiazole, a tetrahydronaphthoselenazole, a tetrahydronaphthoxazole, a tetrahydronaphthindol or a tetrahydronaphthoquinoline, or from a substitution product of any of these.  The dyes are prepared according to known methods: for instance, thiopseudocyanines are prepared by condensing 2 - methyl - tetrahydronaphthothiazole quaternary salt with 2-iodoquinoline methiodide in presence of sodium ethylate; thioisocyanines are prepared by condensing this salt with quinoline ethiodide in presence of alcoholic sodium hydroxide; thiocarbocyanine dyes are derived by condensing this salt with an ester of an orthocarboxylic acid; thiopentacarbocyanine dyes are prepared by condensing this salt with b -ethoxyacrolein acetal; thioheptacarbocyanine dyes are prepared by condensing this salt with a -phenylamino-e -phenylimino - a  : g  - pentadiene hydrohalide; styryl dyes are prepared by condensing this salt with p-dimethylaminobenzaldehyde; the benzene nucleus attached to the thiazole ring may have halogen, alkyl, aryl, or alkoxy substituents.  The dyes derived from a tetrahydronaphthoselenazole, a tetrahydronaphthoxazole, a tetrahydronaphthindol or a tetrahydronaphthoquinoline are obtained in analogous manner from the corresponding bases. Examples describe the manufacture of the following dyes (1) p - dimethylaminobenzylidene - 4,5 - tetra - hydrobenzthiazole ethiodide prepared from 2 - methyl - 6 - 7 - tetramethylenebenzthiazole ethiodide and p-dimethylaminobenzaldehyde reacted in presence of piperidine and alcohol; (2) 1,1<1> - diethyl - 4,5 : 4<1>,5<1>-(bis - tetrahydrobenzo)-benzthiocarbocyanine iodide from the above salt and triethylorthoformate reacted in pyridine; (3) 1,1<1>-diethyl-4,5 : 4<1>,5<1>-(bis-tetrahydrobenzo) - benzthio - ms - methyl - carbocyanine iodide from the salt used in (1), p-toluene sulphonic acid and triethyl orthoacetate reacted in pyridine followed by precipitation with potassium iodide; (4) 1,1<1>-diethyl - 4,5 : 4<1>,5<1> - bis (tetrahydrobenzo)-benzthiopentacarbocyanine iodide prepared from the salt used in (1) and b -ethoxyacroleinacetal reacted in pyridine; (5) 1,1<1>-diethyl-4,5:4<1>,5<1> - bis (tetrahydrobenzo) - benzthioheptacarbocyanine iodide prepared from the salt used in (1) and a -phenylamino-e -phenylimino-a  : g -pentadiene hydrobromide reacted in alcohol in presence of diethylamine; (6) 1,1<1> - diethyl - 6,7 : 6<1>,7<1> - bis (tetrahydrobenzo - ) - benzthio - ms - methyl - carbocyanine iodide derived from 2 - methyl - 4,5 - tetramethylenebenzthiazole p-toluenesulphonic acid ethyl ester and triethylorthoacetate reacted in pyridine followed by precipitation with potassium iodide; (7) 1,1<1>-diethyl-6,7 : 6<1>,7<1>-bis - (tetrahydrobenzo - ) - benzthio - ms - ethyl - carbocyanine iodide prepared from the salt used in (6) and triethylorthopropionate reacted in pyridine followed by precipitation with potassium iodide; (8) 1,1<1> - diethyl - 5,5<1>-diethoxy - 6,7 : 6<1>,7<1> - bis(tetrahydrobenzo - ) - benzthiocarbocyanine iodide prepared from 2 - methyl - 4,5 - tetramethylene - 6 - ethoxybenzthiazole-p-toluenesulphonic acid ethyl ester and triethyl orthoformate reacted in pyridine.  Samples have been furnished under Sect. 2 (5) of dyes prepared as follows: (a) 1,2,3,3-tetramethyl-b -tetrahydronaphthindoleninium iodide reacted with ethyl orthoformate in pyridine followed by precipitation with sodium perchlorate; (b) tetrahydro-b -naphthoquinaldine diethyl sulphate reacted with chloroform in alcoholic sodium methylate followed by precipitation with potassium iodide; (c) 2-methyl-b ,b <1> - tetrahydronaphthoselenazole diethyl sulphate reacted with ethyl orthoformate in pyridine followed by precipitation with potassium bromide; (d) 2-methyl-b ,b <1>-tetrahydronaphthoselenazole diethylsulphate reacted with ethylorthopropionate in pyridine followed by precipitation with sodium perchlorate; (e) 2 - methyl - b ,b <1> - tetrahydronaphthoselenazole dimethylsulphate reacted with a -(o-methyl-phenylamino) - e  - (o-methylphenylimino)-a  : g -pentadiene hydrobromide reacted in alcohol in presence of diethylamine followed by precipitation with potassium iodide : f) 2-methyl-b ,b <1>-tetrahydronaphthoxazole dimethylsulphate reacted with ethyl orthoformate in pyridine followed by precipitation with potassium iodide.  Hydrogenated heterocyclic bases, the salts of which are used above, are prepared analogously to known methods; thus they may be prepared according to the method of Fries.  Accordingly, 2-methyl-4,5-tetramethylenebenzthiazole is prepared by acetylating 1-amino-5,6,7,8-tetrahydronaphthalene, converting this to the thioaceto derivative and oxidizing with potassium ferricyanide; 2-methyl-6,7-tetramethylenebenzthiazole is prepared analogously from 2-amino-5,6,7,8-tetranaphthalene and 2-methyl - 4,5 - tetramethylene - 6 - ethoxybenzthiazole from 1-acetylamino-5,6,7,8-tetrahydronaphthalene-4-naphthol ethyl ether (prepared by acetylating 1-amino-4-naphthol ethyl ether and hydrogenating this).  2-Methyl-tetrahydronaphthindol is prepared from 2-amino-5,6,7,8-tetrahydronaphthalene by way of the hydrazide according to Fischer's synthesis. 2-Methyl-b ,b <1>-tetrahydronaphthoselenazole is prepared by nitrating 2-acetylamino-5,6,7,8-tetrahydronaphthalene, saponifying, converting this according to Bauer's method to the corresponding o-diaminodiselenide and reacting this with acetic anhydride and zinc dust. 2-Methyl-b ,b <1>-tetrahydronaphthoxazole dimethylsulphate is prepared by coupling diazotised sulphanilic acid with tetrahydro-b -naphthol, reducing this with alkaline hydrosulphite, acetylating the resulting b -amino derivative and dry distilling this.