Diazole-4-thiones

3-Diazole-4-thiones (Anhydro-4-mercapto-l,3-diazolium Hydroxides) (103) 

Meso-ionic l,3-diazole-4-thiones (103, R1 = Ph) have been prepared by 1,3-dipolar cycloaddition of phenylisothiocyanate to meso-ionic 1,3-oxazol-5-ones (66)62 and l,3-thiazol-5-ones (105).63 Another route to l,3-diazole-4-thiones is exemplified by the formation of the derivative (103, R1 = R3 = Me, R2 = R4 = Ph) from the methiodide (104) and methylamine.59 

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The constitution (110, Ar = p-Br. CjH4) was firmly established by X-ray crystallography. The corresponding derivative (110, Ar = p-OjN. CjHJ yields a methiodide which gives meso-ionic l,3-diazole-4-thiones (103) with primary aliphatic amines. " The meso-ionic 1,3-thiazole-5-thiones (109) give the salts (113) with methyl iodide. ... 

Similarly, the reaction of cyclic nitrones 187 with methyl isothiocyanate gives tetrahydroimidazo[l,5- ][l,2,4]oxa-diazol-2(l//)-thiones 129 (Equation 81) <2003PS(178)881, 2004MI7>. 

Thieno[2,3-r 1-l,2,3-thiadiazoles 40a-f heated with CS2 in a double compartment autoclave produced thieno[2,3-rfl-l,3-dithiol-2-thiones 41a-f <2001MOL145>. In addition to the thermolysis product 41e, thieno[2,3- / -l,2,3-thia-diazoles 40e also produced bisthieno[2,3-/ 2, 3 -< ][l,4]dithiine 42 in 36% yield (Equation 3). 

Upon heating in boiling toluene in the presence of excess triphenylphosphine, l,3-dithiolo[4,5-c] [l,2,5]thiadiazole-5-thione underwent desulfurization to afford 5-[l,3]dithiolo[4,5-c][l,2,5]thia-diazol-5-ylidine (13) (Equation (6)). When trialkylphosphines were used instead of triphenylphosphine a complex mixture of products resulted <93H(35)69>. 

Azothiadiazoles have been prepared by oxidation of aminothia-diazoles with calcium hypochlorite. More recently, Petri and Glemser obtained a new azothiadiazole, 2,2 -azo-l,3,4-thiadia-zoline-5(4)-thione (76), by oxidation of hydrazinium dithiocarbazate... 

As will be discussed later (Section V,C), mercapto-1,3,4-thia-diazoles have been shown to exist mainly as the tautomeric thiones. They can be prepared in different ways ... 

The 1,3,4-thiadiazole ring is rather susceptible to attack by strong nucleophiles. Thus, the parent compound is stable to acids but is readily cleaved by bases. 2-Amino- and 2-hydrazino-l,3,4-thia-diazoles can be rearranged to l,2,4-triazoline-3(2)-thiones. Goerdeler and Galinke showed that 2-amino- and 2-methylamino-1,3,4-thiadiazole (128, R = H and CH3) are rearranged by methylamine in methanol at 150° to the isomeric triazolinethiones (129). The 5-methyl... 

Janniah and Guha18S>189 reported that 2-amino-l-thia-3,4-diazol-5-thione (158) exists in two forms the sterically-unaceeptable bridged structure 159 was postulated for one of these forms. Bambas190 suggests instead that the two forms may be the individual tautomers 160 and 161. The second explanation is hardly more probable than the first, and the whole problem needs reinvestigation. Certain related compounds with a substituted-amino group have been shown by ultraviolet spectral comparisons to exist in the thione form.190 ... 

Reaction of thio- and alkylthio derivatives of A -aminoazoles with aryl isothiocyanates leads to annelation of a 1,3,4-thiadiazole or a 1,2,4-triazole ring. Thus, 4-amino-3-methyl-l,2,4-triazoline-5-thione, on reaction with aryl isothiocyanates under mild conditions, gives products of addition (388), which on heating are transformed to 2-arylaminotriazolo[3,4-/>]thia-diazoles (389) (83S411 87JHC1173). 

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