Patent GB-800244-A (GB)
Title: Merocyanine dyes, processes for making them and photographic silver halide emulsions containing them
IPC: G03C1/22
Filed: 1956-08-29
Abstract: Substituted 2-thiohydantoins of the general formula <FORM:0800244/IV (b)/1> wherein R4 and R5 are alkyl groups of 1 to 7 carbon atoms, cycloalkyl, mononuclear aryl or aralkyl groups or pyridyl, quinolyl, substituted pyridyl or substituted quinolyl groups, at least one of R4 and R5 being pyridyl, quinolyl, substituted pyridyl or substituted quinolyl, are prepared by heating a compound of the formula R4NHCH2COOR6 (where R6 is an alkyl group o 1-4 carbon atoms) or R4NHCH2CN with a compound of the formula R5NCS or R7NH(R7 being an alkyl group of 1-4 carbon atoms).  When using compounds of the formula R4NHCH2CN, the iminothiohydantoin first obtained must be hydrolysed with mineral acid.  3 - Ethyl - 1 - (2 - pyridyl) - 2 - thiohydantoin is prepared by heating ethyl N-(2-pyridyl) glycine with ethyl isothiocyanate.  The corresponding 3-n-heptyl, 3-methyl, 3-phenyl, 3-cyclohexyl, and 3 - allyl - 1 - (2 - pyridyl) - 2 - thiohydantoins are similarly prepared using the appropriate isothiocyanate. 3-Ethyl-1-(6-methyl-2-pyridyl)-2-thiohydantoin is similarly prepared from ethyl N-(6-methyl-2-pyridyl)-glycine and ethyl isothiocyanate.  1-Phenyl-3-(2-pyridyl)-2-thiohydantoin is prepared from methyl N-(2-pyridyl)-dithiocarbamate and PhNHCH2CO2Et. 1 - (2 - Pyridyl) - 3 - (2 - pyridyl) - 2 - thiohydantoin is similarly prepared, and 1-n-heptyl-3-(2-pyridyl)-2-thiohydantoin is prepared from ethyl N-(2-pyridyl)-dithiocarbamate and ethyl N-n-heptylaminoacetate. The 3-(3-pyridyl)-, 3-(6-methyl-2-pyridyl)-, 3-(4-methyl-2-pyridyl)-, and 3 - (3 - quinolyl) - 1 - (2 - pyridyl) - 2 - thiohydantoins and 1,3-di-(6-methyl-2-pyridyl)-2-thiohydantoin are similarly prepared from N-substituted methyldithiocarbamates and N-substituted-ethyl glycines. 3-Benzyl-1-(2-pyridyl)-2-thiohydantoin is prepared from C6H5.CH2NHCS2Et and ethyl - N - (2 - pyridyl) - glycine.  1 - Ethyl - 3 - (2 - pyridyl) - 2 - thiohydantoin is prepared from EtNHCH2CN and methyl-N-(2-pyridyl)-dithiocarbamate and treating the imino compound formed with 5N-HCl.  Triethylammonium N-(2-pyridyl)-dithiocarbamate is prepared by warming 2-aminopyridine with carbon disulphide and triethylamine. Treatment of the triethylammonium salt with methyl iodide or ethyl bromide gives methyl-N-(2-pyridyl)-dithiocarbamate or ethyl-N-(2-pyridyl)-dithiocarbamate respectively. 3-Aminopyridine, 4-aminopyridine, 4-methyl-2-aminopyridine, 6-methyl-2-aminopyridine and 3-aminoquinoline are similarly warmed with CS2 and NEt3, and the products treated with methyl iodide to give N-substituted methyl dithiocarbamates. Methyl - N - (3 - pyridyl) - dithiocarbamate is heated to give 3-pyridyl isothiocyanate. Ethyl - N - (2 - pyridyl) - glycine is prepared by refluxing N - (2 - pyridyl) - aminoacetonitrile with concentrated sulphuric acid in ethanol.  Ethyl - N - (6 - methyl - 2 - pyridyl) - glycine is similarly prepared. N - (6 - Methyl - 2 - pyridyl) - aminoacetonitrile is prepared by heating sodium bisulphite, formalin and 6-methyl-2-aminopyridine, and adding aqueous sodium cyanide to the product.ALSO:Merocyanine dyes of the general formula: <FORM:0800244/IV (c)/1> wherein R is an alkyl, substituted alkyl, allyl or aralkyl group, n is 0 or 1, d is 0, 1 or 2, Z completes a 5- or 6-membered heterocyclic ring and R4 and R5 represent alkyl groups of 1-7 carbons, cycloalkyl, mononuclear aryl, aralkyl, pyridyl, substituted pyridyl, quinolyl or substituted quinolyl groups, at least one of R4 and R5 being a substituted or unsubstituted pyridyl or quinolyl group, are prepared by condensing a compound of the formula: <FORM:0800244/IV (c)/2> (for dyes wherein d = 0) or of the formula: <FORM:0800244/IV (c)/3> (for dyes wherein d = 1 or 2), with the appropriate cyclic ketomethylene compound (X represents an anion, R1 is alkyl or aryl, R2 is acyl and R3 is aryl). In the examples, R is methyl or ethyl, Z completes a thiazoline, benzthiazole, a - or b -naphthathiazole, 4,5-diphenyloxazole, benzoxazole or a - or b -naphthoxazole nucleus, R4 is 2-pyridyl, 6-methyl-2-pyridyl, ethyl, phenyl or n-heptyl, and R5 is methyl, ethyl, n-heptyl, allyl, benzyl, phenyl, 2-pyridyl, 2-pyridyl, 4-methyl-2-pyridyl, 6-methyl-2-pyridyl or 3-quinolyl, such that either R4 or R5 is always one of the specified pyridyl or quinolyl groups.