Thiazolo-l,3,4-thiadiazoles

Thiazolo[2,3-h]-l,3,4-thiadiazoles [C2N2S-C3ISS]. The reaction between l,3,4-thiadiazole-2(3//)-thiones and phenacyl bromide gives sulphides, e.g. (122 R = NHAc), which may be cyclized to the thiazolo[2,3-/ ]-1,3,4-thiadiazolium salts (123 R = NHAc), whilst with PhCHBrCOCl the anhydro-5-hydroxy-2-methyl-6-phenylthiazolo[2,3-6]-l,3,4-thiadiazolium hydroxide (124 X = N) is readily obtained.  

Thiazolo-[2,3-b]- and -[5,4-d]-thiazoles [C3NS-C3NS]. By means of a method similar to that of the previous reaction, thiazole-2(3//)-thione may be readily converted into anhydro-3 -hydroxy-2 -phenylthiazolo[2,3 -6 Jthiazolium hydroxide (124 X = CH). 2-Acetylamino-5-amino-4-thiocyanatothiazole cyclizes, on heating in methyl benzoate, to give the thiazolo[5,4-c/]thiazole derivative (125).  

Imidazo[2,l-h]thiazoles [C3NS-C3N2]. Further examples of the reaction between 2-amino-thiazoles (or -thiazolines) and a-bromo-ketones to give imi-dazo[2,l-6]thiazoles (126) have been reported this ring system has also been obtained from imidazolidine-2-thione and a-bromo-ketones, or pro-pargyl bromide, and from l-(2-methoxyethyl)-4-phenylimidazolidin-2-one 

Abignente, F. Arena, M. Carola, P. DeCaprariis. A. P. Caputi, F. Rossi, L. Giordano, C. Vacca, E. 

Nielek andT. Lesiak, Collect. Lect. Int. Symp. Furan Chem., 3rd, 1979, 224 (Chem. Abstr., 1980, 

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