Diamino- 1,2,4-thiadiazoles properties

Diamino-1,2,4-thiadiazoles of type (361) have been patented for use in the treatment of hypertension <82EUP44266), while 5-amino-1,2,4-thiadiazoles such as (362) are claimed to be useful for treating autoimmune diseases and in the prevention of graft rejection. Compounds of type (362) also have antirheumatic properties and are, in particular, useful in the treatment of rheumatoid arthritis and immune diseases such as systemic lupus <91EUP455356). 

Azole approach. 3,4-Diamino-l,2,5-thiadiazole reacts with 1,2-dicarbonyl compounds to form pyrazines (747) (76JHC13). From the reaction of 1,2,5-thiadiazole 1,1-oxides such as (748) with o-phenylenediamine, the l,3-dihydro[l,2,5]thiadiazolo[3,4-Z>]quinoxaline 2,2-dioxide (749) is formed. To understand this reaction it is pointed out that the 1,2,5-thiadiazole 1,1-dioxide ring is to be regarded as alicyclic rather than aromatic and is strongly 7r-electron deficient. Substituents with leaving properties in the 3,4-positions are therefore readily displaced as in the reaction of (748) (75JOC2743). 

Diamino-l,2,4-thiadiazole possesses radioprotective activity3, a correlation has been established466 between this property and a depressive effect on thymidine uptake on myelocytes, and on the rate of DNA synthesis in bone marrow and intestinal epithilium. The radioprotective activity of 5-amino-3-methylthio-l,2,4-thiadiazole has also been reported.467... 

Pure (192) is a white crystalline solid resembling naphthalene in its physical properties. Its high degree of symmetry is reflected in the simplicity of its i.r. spectrum. Hydrolysis yields successively 3,4-diamino-l,2,5-thiadiazole, oxamide, and sulphur. ... 

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