Other Fused Isothiazoles

Naphtho[l,2-c]isothiazole (52) and its [2,1-c] isomer (53) can be prepared from the corresponding methylnaphthaleneamines by a reaction similar to that described above the linear isomer (54) is not obtainable in this way.65 

Reaction of the aminouracil (55) with thionyl chloride in dimethyl-formamide produced the isothiazolo[3,4- /]pyrimidine (56).66 

---

Thiete structures have been suggested as fragmentation products in the mass spectra of a thietane fused to a 3-lactam, an ortho disulfide of a thiolbenzoate ester, -propanethiol, thiirane carboxylic acid esters, isothiazoles, thiazoles, 1,3-dithiole 2-thiones, 1,3-dithiolene-2-ones, S-ethyl thio-benzoate, and thianaphthene sulfones. Tetramethylthiete may have been formed on thermolysis of the p-toluenesulfonyl-hydrazone of 2,2,4,4-tetramethyl-3-thietanone. " Thiete 2-thione may be an intermediate in the decomposition of 1,2-ditholium salts by the action of bases. " 2,2-Diphenyl-2H-thiete is suggested as an intermediate in the reaction of diphenyldiazomethane with 1,2,3-benzo-thiadiazole which yields 9-phenylthioxanthene and three other products. ... 

Included among other isothiazoles are compounds closely related to benzisothiazoles naphthoisothiazoles and systems with two or more isothiazole rings fused to a single benzene ring. Compounds which have a thiophene or pyridine ring, etc., fused to an isothiazole are omitted. 

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-... 

---