Oxidative 2-methylbenzothiazole

Numerous cationic azo dyes are prepared by the action of /V-hydroxymcthyl-chloroacetamide on azo dyes in sulfuric acid medium, followed by displacement of the reactive chloro substituent by pyridine or trialkylamine. Of special significance for dyeing paper are dyes that are prepared by coupling of diazotized 2-(4 -aminophenyl)-5-methylbenzothiazole to acetoacetaiylides, pyrazolones, naphthols [143], or barbituric acid derivatives [144], followed by reaction with N-hydroxymethylchloro-acetamide and pyridine. The azo dye obtained by oxidative dimerization of 2-(4 -aminophenyl)-5-methylbenzothiazole may also be subjected to this conversion [145], Dye 51 colors paper yellow. 

Indeed, benzoxazoles and benzothiazoles react smoothly with secondary and primary aliphatic amines in acetonitrile in the presence of benzoic acid and silver carbonate, thus giving rise to the corresponding 2-amino derivatives (Scheme 40) [94]. Also the reaction of 6-methylbenzothiazole with morpholine has been carried out in the presence of Zn(OAc)2 as the Lewis acid (catalyst) and Ag20 as oxidant. 

A stoidiiometric amount of trifluoroacetic acid added to an ice-cooled soln. ot trans-stilh ne oxide and 3-methylbenzothiazole-2-selone in methylene diloride tra 5-stilbene. Y 97% similarly from traw -stilbene sulfide in refluxing methylene diloride, Y 95%. F. e. s. V. Calo et al.. Synthesis 1976, 200 from oxido compds. with inversion of configuration (cf. Synth. Meth. 27, 942) by dimethyl-phenylsilyllithium cf. M. T. Reetz and M. Plachky, ibid. 1976, 199. 

In view of the versatility of 3-methylbenzothiazol-2-one hydrazone as a starting material for producing heterocyclic azo-compounds by oxidative coupling, the isomeric 2-methyl-l,2-benzisothiazol-3-one hydrazone has been synthesized (from the corresponding 3-chloro-derivative), and its coupling with dimethylaniline and l-hydroxy-2-naphthoic acid anilide has been examined, ... 

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