New dyes based on 3-aryl-benzo- and -naphtho-1,4-thiazines
Abstract
3-Aryl-2H-1,4-benzothiazines have been converted into cyanine dyes by condensing their hydroperchlorates with aldehydes, and into azo-compounds by coupling with reactive diazonium salts. The azo-compounds were also obtained by condensing arylglyoxal hydrazonyl bromides with o-aminothiophenol; they exist predominantly in their tautomeric hydrazone forms. 2-Amino-3-mercapto-1,4-naphthoquinone condenses with ω-bromoaceto-phenones to form 3-aryl-3,4-dihydro-3-hydroxy-2H-naphtho[2,3-b]-1,4-thiazine-5,10-quinones. Attempts to dehydrate these carbinolamines gave a variety of products. Oxidation of the phenyl analogue with iodosobenzene diacetate led to acetyoxylation at C-2 by an indirect Pummerer oxidation.
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