Synthesis and structure elucidation of 2-[2-aza-(1-(3-hyroxyphenyl)vinyl)]-5,6-dimethylbenzothiazole, 2-[2-amino-(1-(3-hyroxyphenyl)methylen]-5,6-dimethylbenzothiazole and 3-{[N-(5,6-dimethylbenzothiazole-2-yl)2-chloroacetylamino]methyl}phenyl-2-chloroacetate