Thiadiazole-2-thiones

4-Thiadiazole-2-thiones (Anhydro-2-mercapto-l,3,4-thiadiazol-ium Hydroxides) (251) 

Although these substances have been known since the early investigations by Busch,2b,9b recent interest has been stimulated by their 

It has been shown that the transformation 254 - 251 + 253 proceeds with first-order kinetics and that increase in solvent polarity is associated with an increase in the rate. It is proposed that the reaction involves a novel unimolecular heterolytic scission of the sulfur-sulfur bond in the symmetrical disulfide (254).1 The kinetics of the alkaline hydrolysis of anhydro-2-mercapto-4,5-diphenyl-l,3,4-thiadiazolium 

The thermal isomerization 251 - 256 has been shown to occur in cases where R1 = Me.164 

The valence tautomerism 251 257 has been proposed22,137 to account for the formation of JV-methylthiobenzamide by irradiation (2537 A) in methyl cyanide solution. The valence tautomer 257, R1 = 

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An original method has recently been developed starting either from 1.3-dithiolane (10) or from 1.3.4-thiadiazole-2-thione derivatives (11) (Scheme 4) (3). This method does not work when Ri is an aryl group. 

The UV-Vis spectra of the noncoordinated 5-amino-37/-l,3,4-thiadiazole-2-thione 26 and its organotin(iv) complex exhibit two absorption bands at 256 and 318 nm assigned to the 7t-7t and n-jt transitions of the C=N chromophore, respectively <2006SAA148>. These bands undergo a hyperchromic shift upon complexation supporting the participation of the C=N group in the coordination. 

The thiadiazole thione 112 was treated with an alkyl halide in sodium hydroxide to afford the thiadiazole derivatives 113 in 35-92% yields (Equation 35, Table 3) < 1999JME1161 >. This reaction results in the aromatization of the reduced thiadiazoline ring (see Section 5.10.9.5.1). The 2-(methylsulfanyl)-l,3,4-thiadiazoles can be S-demeth-ylated to afford 1,3,4-thiadiazole-2-thiones <1994JHC1439>. 

The allylation of thiadiazole-2-thione 114 with ally 1 bromide gave as the main product the N-allyl derivative 115 with trace amounts of the corresponding S-derivative 116 (Equation 36) <2003CHE228>. Furthermore, it was shown that refluxing the thiadiazole 116 in DMF (3h) gave thiadiazole-2-thione 115 via a thio-Claisen rearrangement. 

The reaction of 5-amino-37/-l,3,4-thiadiazole-2-thione 452 with 2,3-dichloro-l,4-naphthoquinone 453 in DMF, at room temperature (rt) for 48 h, gave the complex naphthoquinoimidazolothiadiazole 454 (Equation 104) <1996PS(116)261>. 

The disodium salt (82) prepared from the dichloride (81) reacted with thiophosgene to afford 1,3-dithiolo[4,5-c][l,2,5]thiadiazole-2-thione in 37% yield (Scheme 19) <93H(35)69>. 

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