Fused to other Nitrogen-containing Heterocycles

Isothiazoles Fused to other Nitrogen-containing Heterocycles.—In view of the ease with which, in the laboratory at least, an isothiazole ring may be fused to biological nitrogen heterocycles, it is, perhaps, surprising that no naturally occurring isothiazole has yet been found. Typical recent work includes the efficient synthesis of isothiazolo[3,4-d]pyrimidines (114 X = NHR or SMe), of isothiazolo[4,5-i l- 

Takahashi, N. Nimura, and H. Ogura, Chem. Pharm. Bull., 1979, 27, 1147 H. Okuda, Y, Tominaga, Y. Matsuda, and G. Kobayashi, Yakugaku Zasshi, 1979, 99, 989 Chem. Abstr., 1979, 92, 128 845). 

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