1.3.4- Thiadiazole, base-catalyzed exchange

Thiadiazole is a planar, thermally stable, and weakly basic aromatic ring system. Aromatic forms of the 1,2,5-thiadiazole nucleus are generally stable to concentrated mineral acids and are only slightly sensitive to base. Base-catalyzed deuterium exchange of the ring protons can be effected... 

Addition of nucleophiles to the cyano group of cyanothiadiazole under basic conditions takes place with unusual ease <88AG(E)434,94ACS372). Hydrolysis to the amide, for example, can be effected at 0°C in the presence of a catalytic amount of sodium hydroxide or basic ion-exchange resin. At reflux temperature, hydrazine and monosubstituted hydrazines convert 3,4-dicyano-l,2,5-thia-diazole into the l,2,5-thiadiazole[3,4-. The base-catalyzed addition of acetone to cyanothiadiazole forms an enamino ketone, used as a key intermediate for the synthesis of a number of heterocyclic ring systems, e.g. isothiazole, isoxazole, pyrazole, pyrimidine, and thiazole <77H(6)1985>. 

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