Process of preparing beta-substituted polymethine dyestuffs

2-(2 - Methylmercapto - 3 - p - dimethylaminobenzalpropenyl)-benzthiazole ethiodide is prepared by boiling together 2-(2-methylmercaptopropenyl)-benzthiazole ethyl methosulphate, p-dimethylaminobenzaldehyde and acetic anhydride, and treating the product with aqueous potassium iodide solution. 1 - Phenyl - 3 - methyl - 4 - (31 - ethyldihydrobenzthiazolylidene - g - methylmercaptobutenylidene)-5-pyrazolone is prepared by reacting together 2 - (2 - methylmercaptopropenyl) - benzthiazole ethyl methosulphate, 4-anilidomethylene - 1 - phenyl - 3 - methyl - 5 - pyrazolone, acetic anhydride, and sodium acetate. 2 - (2 - Phenylmercaptopropenyl) - benzthiazole ethochloride is prepared by reacting 2-(2-chloropropenyl) - benzthiazole ethochloride with sodium thiophenolate. 2 - (2 - Methoxypropenyl) - benzthiazole ethiodide is prepared by reacting 2-acetylmethylene-N-ethylbenzthiazoline with methyl iodide. Samples have been furnished under Sect. 2 (5) of five dyes, the preparation of the intermediates for which is as follows. 2-(b -ethoxy: b - methylvinyl) - benzoelenazole methyl ethyl sulphate is prepared by refluxing 2-acetylmethylene - N - methyldihydrobenzselenazole with diethyl sulphate and benzene, 2-(b -ethoxy: b -methylvinyl)-6-methylbenzthiazole methyl ethyl sulphate, 2-(b -ethoxy: b -methylvinyl)-benzthiazole benzyl ethylsulphate, and 2-(b -methoxy: b -methylvinyl) - 3 : 4 - (a - methyltrimethylene) - benzthiazole dimethylsulphate are similarly prepared. N - Acetyl - 2 - methyl - 1 : 2 : 3 : 4 - tetrahydroquinoline is prepared by boiling 2-methyl-1 : 2 : 3 : 4-tetrahydroquinoline with acetic acid and acetic anhydride. N-Thioacetyl-2-methyl-1 : 2 : 3 : 4-tetrahydroquinoline is prepared by refluxing the N-acetyl compound with P2S5 in toluene. 2 - Methyl - 3 : 4 - a - methyltrimethylenebenzthiazole bromide is prepared by reacting the N-thioacetyl compound with bromine in chloroform. 2 - Acetyl - methylene - 3 : 4 - a - methyltrimethylenedihydrobenzthiazole is prepared by reacting 2-methyl-3 : 4-a -methyltrimethylenebenzthiazole bromide in pyridine with acetaldehyde. 2-(b -Chloro-b -methylvinyl)-benzthiazole ethochloride is prepared by reacting 2-acetylmethylene - N - ethyl - 2 : 3 - dihydrobenzthiazole in benzene with POCl3. 2-(b -Benzthiazolylmercapto: b - methylvinyl) - benzthiazole ethochloride is prepared by adding the b -chloro compound to a warm solution of the potassium salt of 2-mercaptobenzthiazole in pyridine. Specification 623,990 is referred to.ALSO: