6-Methylimidazo [2, 1-b]-1, 3, 4-thiadiazoles (III
1, 2) were prepared in a good yield by treatment of 2-amino-1, 3, 4-thiadiazoles (I
1, 2) with bromoacetone in H
2O for 1 hr at 95-100°. Six kinds of 6-phenylimidazo [2, 1-b]-1, 3, 4-thiadiazoles (VI
1-6) were obtained in a good yield by treatment of 2-imino-3-phenacyl-△
4-1, 3, 4-thiadiazoles (V
1-6) with polyphosphoric acid (PPA) for 2 hr at 135-140°. Thiocyanation of III
1, 2 and VI
1-6 was carried out by the bromine method and the urea method, and the corresponding 5-thiocyanato derivatives (VII
1-8) were obtained in a good yield. The preparation of 5-methylthiazolo [3, 2-b]-s-triazoles (XII
1, 2) was effected in a good yield by treatment of 3-(2-propynylthio)-1, 2, 4-triazole hydrobromides (X
1, 2) with two equivalents of sodium ethoxide in ethanol, and XII
2 was also obtained by treatment of 3-acetonylthio-5-methyl-1, 2, 4-triazole (XII
2') with PPA for 2 hr at 140-145°. Six kinds of 5-phenylthiazolo [3, 2-b]-s-triazoles (XIV
1-6) were prepared in a good yield by treatment of 3-phenacylthio-1, 2, 4-triazoles (XIII
1-6) with PPA for 2 hr at 150-160°. Thiocyanation of XII and XIV did not proceed, whereas the corresponding 6-bromo derivatives (XV
1-8) were obtained in a good yield by bromination of XII
1, 8 and XIV
1-6.
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