6-Amino-thiazolo4,5-cisothiazole derivatives4are obtained by addition of hydrogen sulfide to the 4-Amino-thiazoline-5-carbonitrile2followed by cyclooxidation of the intermediate thioamides3. In the presence of sodium sulfite the hydrolysis of the4-amino-2-methylthio-thiazolium salts5derived from the title compounds1yields the4-amino-thiazolin-2-ones6. By their further hydrolysis the 2,4-dioxo-thiazolidin-5-carboxamides8are formed. The 2-oxo-and 2-thioxo-thiazolo 4,5-dpyrimidin-7-ones and -thiones available from1undergo ring opening by hydrolysis to give the substituted 4-amino-6-oxo- and 4-amino-6-thioxo-pyrimidine-5-thiols15a–hand13i–e. They have been isolated as their disulfides14or 5-alkyl derivativesi.e.the substituted 4-amino-5-alkylthiopyrimidin-6-ones and -thiones16. In analogy, the intermediate 6-amino-7-oxo-thiazolo4,5-d pyrimidin-2-thione18and the 7-amino-thiazolo4,5-d-pyrimidin-2-thione24derived from1react by ring cleveage to yield the 1,4-and 4,6-diamino-pyrimidin-5-thiole derivatives22and27, respectively, isolated as their disulfides or alkylthio-derivatives. From the pyrimidine16bthe pyrimido5,4-b1,4-thiazine derivative18can be obtai
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