2-Hydroxythiazoles, synthesis

Hydroxythiazoles give 2-chIorothiazole derivatives almost quantitatively upon treatment with phosphorus oxychloride (221, 229, 428). This constitutes a convenient synthesis method for these compounds when the conversion of 2-aminothiazoles to 2-chlorothiazole derivatives fails. Esters of thiocarbamic acid or thiourethanes also react with a-halocarbonyl compounds to give the corresponding 2-alkoxythiazoles (50, 68, 209, 272). 

Suzuki, N., Sato, M., Nishikawa, K., and Goto, T. (1969). Synthesis and spectral properties of 2-(6 -hydroxybenzothiazol-2 -yl)-4-hydroxythiazol, a possible emitter species in the firefly bioluminescence. Tetrahedron Lett. 55 4683-4684. 

A novel application of the Ritter reaction to the synthesis of 2-hydroxythiazoles was reported recently by Yura,19 using acetylenic thiocyanates. 

Synthesis from nitriles and a-mercapto ketones or acids 2,4-disubstituted and 4-hydroxythiazole derivatives (Type D)... 

Hydroxythiazole, from chloroacetaldehyde and ammonium thiocaibamate, 258 4-Hydroxy-2-thiazolecarboxylic acid ethyl ester, self condensation of, 294 synthesis of, from ethylcyanoacetate and ethylthioglycolate, 294 from thioamides and a-haloacids or esters, 294... 

Synthesis. - Hantzsch s Synthesis (Type A S—C—N + C-C) From thioureas. Starting from thioureas, the following compounds have been obtained 2-amino-4-(4-benzyloxyphenyl)thiazoles, 2-(2-amino-5-hydroxythiazol-4-yl)-1 -(4-chloro-3-methylphenyl)ethanone, 2-benzylidenehydrazino-4-( 1,5 -di-... 

Thiazolin-4-one derivative 29 in hydrazino-hydrazono tautomeric equilibrium is synthesized by cyclization of l,2-diaza-l,3-butadiene 27 with aryl thioamide 28. Subsequent hydrolytic removal of the NH-Boc-hydrazo protecting group provided 5-acetyl-4-hydroxythiazole derivative 30a, which undergoes a-bromination to give a-bromomethyl ketone 30b. This bromide is used to prepare polyfunctionalized 4,5 -bithiazol-4 -ol derivatives via the Hantzsch thiazole synthesis <04SL2681>. 

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