Patent GB-589965-A (GB)
Title: Improvements in cyanine dyes
IPC: C09B23/12
Filed: 1944-08-21
Abstract: Cyanine dyes are prepared by condensing one molecular proportion of a quaternary salt of a heterocyclic nitrogen compound, bearing in the a - or g -position to the nitrogen atom a symmetrical or unsymmetrical b b -di-(alkyl or aralkyl)-mercaptovinyl substituent with two molecular proportions of the same or different compounds, each being a quaternary salt of a heterocyclic nitrogen compound carrying in the a - or g -position to the nitrogen atom a reactive methyl substituent, at least one of the quaternary salts being a quaternary salt of 1 : 5-phenanthroline having one of the specified substituents in the 2-position and optionally further substituents elsewhere.  The quaternary salt with the reactive methyl substituent may be 2 : 6-dimethyl-1 : 5-phenanthroline methyl p-toluenesulphonate, 6-ethoxyquinaldine ethyl p - toluenesulphonate, 4 - a  - furyl - 3 - methyl - thiazole methyl p-toluenesulphonate, 2 : 6-dimethyl - 1 : 5-phenanthroline ethiodide, lepidine ethiodide, 2-methylbenzselenazole ethiodide, 2 : 6 - dimethyl - 1 : 5 - phenanthroline methiodide, 2 : 3 : 3-trimethylindolenine ethiodide, 2-methyl-6-phenyl-1 : 5-phenanthroline-8-carboxylate ethosulphate, lepidine benzyl chloride, or 2-methylthiazoline ethiodide.  The b  : b  - di - (alkyl or aralkyl) - mercaptovinyl quaternary salt may be 2-b  : b -dimethylmercaptovinyl - 6 - methyl - 1 : 5 - phenanthroline methyl p-toluenesulphonate, 2 - b  - methylmercapto-b -ethylmercaptovinyl-1 : 5-phenanthroline ethyl p - toluenesulphonate, 2 - b  : b  - dimethylmercaptovinyl - 6 - methylbenzthiazole ethyl methylsulphate, 2-b -methylmercapto-b -ethylmercaptovinyl-1 : 5-phenanthroline methyl p - toluenesulphonate, 2 - b  : b  - methylmercaptovinylbenzthiazole ethiodide, 2 - b  : b  - methyl - mercaptovinyl - 6 - methylbenzthiazole ethyl p - toluenesulphonate, 2 - b  : b  - methylmercapto - vinylquinoline methyl p-toluenesulphonate, or 2-b  : b -methylmercaptovinyl-1 : 5-phenanthroline ethyl p-toluenesulphonate.  The condensation may be effected in presence of an acid-binding agent such as pyridine, triethanolamine, or triethylamine.  In example 1, 1 : 6-dimethyl-2-dithiocarbomethoxymethylene-1 : 2-dihydro-1 : 5-phenanthroline is mixed with methyl p-toluenesulphonate and 2 : 6 - dimethylphenanthroline and heated, the cooled mixture is dissolved in ethanol containing triethylamine and refluxed, and aqueous potassium bromide is added.  In example 2, 1-ethyl-2-dithiocarbomethoxymethylene-1 : 2-dihydro-1 : 5-phenanthroline, 6-ethoxyquinaldine, and ethyl p-toluenesulphonate are fused together, the cooled product is dissolved in boiling pyridine containing triethylamine and refluxed, and aqueous potassium iodide is added.  In example 3, 1 : 6-dimethyl-2-dithiocarbomethoxymethylene-1 : 2-dihydrophenanthroline, 4-a -furyl-3-methylthiazole and methyl p-toluenesulphonate are fused together, the product is dissolved in warm pyridine containing triethylamine and refluxed, and aqueous potassium iodide is added. In example 4, 3-ethyl-6-methyl-2-dithiocarbomethoxymethylene - 2 : 3 - dihydrobenzthiazole and dimethylsulphate are heated together and the product is dissolved in ethanol, 2 : 6-dimethyl-1 : 5-phenanthroline ethiodide is added, triethylamine is added after raising the mixture to the boil, and the mixture is boiled under reflux.  2-b  : b -Dimethylmercaptovinyl-6-methyl-1 : 5-phenanthroline methyl p-toluenesulphonate is prepared by reacting 1 : 6-dimethyl-dithiocarbomethoxymethylene-1 : 2-dihydrophenanthroline with methyl p-toluenesulphonate.  2 - b  - Methylmercapto - b  - ethylmercaptovinyl - 1 : 5 - phenanthroline methyl p - toluenesulphonate is prepared by the action of ethyl p-toluenesulphonate on 1 - methyl - 2 - dithiocarbomethoxy - methylene - 1 : 2 - dihydro - 1 : 5 - phenanthroline.  2-b  : b -Dimethylmercaptovinyl-1 : 5-phenanthroline ethyl p-toluenesulphonate is similarly prepared from methyl p-toluenesulphonate and 1 - ethyl - 2 - dithiocarbomethoxymethylene - 1 : 2-dihydro-1 : 5-phenanthroline. 2-b  : b -Dimethylmercaptovinyl - 6 - methylbenzthiazole ethyl p - toluenesulphonate is similarly prepared.  1 : 6-Dimethyl-2-dithiocarbomethoxymethylene-1 : 2-dihydrophenantholine is prepared by heating 2 : 6-dimethyl-1 : 5-phenanthroline ethiodide with dimethyl trithiocarbonate in pyridine. 3-Ethyl-6-methyl-2-dithiocarbomethoxymethylene-2 : 3-dihydrobenzthiazole is prepared by reacting 2 : 6-dimethylbenzthiazole ethyl p-toluenesulphonate with carbon disulphide and methylating the product with dimethyl sulphate. Specifications 549,202 and 589,964 are referred to.