Patent GB-576234-A (GB)
Title: New yellow azo dyestuffs
IPC: C09B44/02
Filed: 1944-05-08
Abstract: Yellow azo dyestuffs are made by heating a 4 : 41 - dibenzthiazyl - (2) - azobenzene which carries as substituents two alkyl (1-4C)-mercapto or two alkyl (1-4C)- or aralkyl-mercaptomethyl groups and optionally, directly attached to itself or to the said aralkyl-mercaptomethyl groups, one or more halogen, alkyl (1-4C) or alkoxy (1-4C) radicals as nuclear substituents, with a dialkyl (1-4C) sulphate.  The products, which are apparently ternary sulphonium salts, dye cellulosic material in bright yellow shades from a dyebath containing mild alkali, such as sodium carbonate or bicarbonate.  In the examples dyes are made from dimethyl sulphate and chloro-di-(methylmercapto)-4.41-di-(6 - methylbenzthiazyl - 2) - azobenzene, di - (methylmercaptomethyl) - 4.41 - di - (benzthiazyl - 2) - azobenzene, di - (methylmercaptomethyl) - 4.41 - di - (6 - ethoxybenzthiazyl - 2) - azobenzene or di-(methyl-, ethyl-, butyl- or benzyl - mercaptomethyl) - 4.41 - di - (6 - methylbenzthiazyl-2)-azobenzene, and the dyeing of cotton yarn is described.  Reference is also made to the action of dimethyl sulphate on dimethylmercapto-4 : 41-di-(6-methylbenzthiazyl-2)-azobenzene.  A sample has been furnished under Sect. 2 (5) of the dyestuff produced by the action of dimethyl sulphate on di-(methylmercaptomethyl) - 4 : 41 - bis - (4 : 6 - dimethylbenzthiazyl-2)-2 : 21-dimethylazobenzene (obtainable by the action of sodium methyl mercaptide in the presence of b -ethoxyethanol on di-(chloromethyl)-4 : 41-bis-(4 : 6-dimethylbenzthiazyl-2)-2 : 21-dimethylazobenzene.  Chlorodi - (methylmercapto) - 4 : 41 - di - (6 - methylbenzthiazyl - 2) - azobenzene may be prepared by treating 4 : 41-di-(6-methylbenzthiazyl-2)-azobenzene with sulphur chloride-aluminium chloride by the process of Specification 573,831, reducing with sodium sulphide in caustic soda solution, and methylating with dimethyl sulphate or methyl iodide.  Di - (methylmercaptomethyl) - 4 : 41 - di - (benzthiazyl-2)-azobenzene may be prepared by chlormethylating 4 : 41-di-(benzthiazyl-2)-azobenzene (obtainable by oxidation of 2-p-aminophenylbenzthiazole) with dichlorodimethyl ether, and treating the resulting dichloromethyl derivative with methyl mercaptan in the presence of b -ethoxyethanol. Di - (methylmercaptomethyl) - 4 : 41 - di - (6 - methylbenzthiazyl-2)-azobenzene may be prepared in an analogous manner.  Di - (methylmercaptomethyl) - 4 : 41 - di - (6 - ethoxybenzthiazyl-2)-azobenzene may be similarly prepared from 4 : 41-di-(6-ethoxybenzthiazyl-2)-azobenzene (obtainable by oxidation of 2-p-aminophenyl-6-ethoxybenzthiazole which may be made by reduction of the corresponding nitro compound obtainable by condensing the zinc salt of 2-amino-5-ethoxythiophenol with p-nitrobenzoyl chloride). Di-(ethyl-, butyl- and benzyl-mercaptomethyl)-4 : 41-di-(6-methylbenzthiazyl-2)-azobenzene may be made by the action of ethyl, butyl and benzyl mercaptans on di-(chloromethyl)4 : 41-di - (6 - methylbenzthiazyl - 2) - azobenzene in the presence of b -ethoxyethanol in which a small amount of sodium has been dissolved. Dimethylmercapto-4 : 41 - di - (6 - methylbenzthiazyl-2)-azobenzene may be prepared by the action of dimethyl sulphate on the mercaptan solution obtained in the example in the Provisional Specification of Specification 549,532.