1,2,3,5-Thiatriazole S-oxides

The A -l,2,3,5-thiatriazoline A-oxides (20) are stable at room temperature but are easily hydrolyzed <85TL6155>. Sulfinylamines are known to react with carbonyl compounds and so with R = CHjCOPh, R = Me, an intramolecular trapping of the carbonyl group leading to a 6-membered pyrazine might have been expected. However, even in this case, the 1,2,3,5-thiatriazole S-oxide was formed due to preferential reaction with the highly nucleophilic nitrogen over cycloaddition <86H(24)1193>. 

Ring closures with amidrazones 1,2,3,5-Thiatriazole S-oxides... 

This general approach to the 1,2,3,5-thiatriazole ring was also used to prepare l,2,3,5-thiatriazolidine-4-one-l-oxides 36 (X = 0) and 1,2,3,5-thiatriazolidinc l-thione-l-oxides 36 (X = S) by the reaction of semicarbazides 35 (X = O) and thiosemicarbazides 35 (X = S), respectively, with thionyl chloride in methylene chloride solution (Equation 10) <1979JHC895>. 

Generally, the structures of the 1,2,3,5-thiatriazoles (114) and (113 X = S) are inferred from the mode of synthesis. The structure of l,2,3,5-thiatriazoIo[5,4-a]pyridine 3-oxide (117) has been discussed in more detail. 2-Hydrazinopyridine is formed upon hydrolysis and the IR spectrum exhibits an NH stretching vibration at 3280 cm-1. This suggests the interesting possibility of tautomeric and zwitterionic structures (Scheme 8). Methylation with diazomethane gives the 1-methyl derivative which apparently is best formulated as the zwitterionic A4-thiatriazoline (118). UV spectroscopic properties of (117) (Amax 235, 290 and 342) and (118) (Amax 235, 290 and 345 nm) reveal a close structural similarity (63CB2519). A comparative NMR spectroscopic study of (117) and the A3-l,2,3,5-thiatriazo-line (119 R1 = H, R2 = Me) supports the description of (117) as a pyridinium salt (Scheme 9) (70CB1918). 

Zur Umsetzung von 2-Methylaminocarbonyl-l-oxo-2,3-dihydro-lH-indazol mit Thionylchlo-rid zu 3,5-Dioxo-2-methyl-2,3-dihydro-5H-(mdazolo[1,2-b]-1,2,3,5-thiatriazol -1 -oxid (72%) s. Lit.500... 

CN3S s N N N — 5-Phenyl-l,2,3,4-thiatriazole 5-amino-l,2,3,4-thiatriazole 5-phenyl-1,2,3,4-thiatriazole 3-oxide... 

The 1,2,3,5-oxatriazoles are known as oxatriazolines (112,113 X = O) and the thiatriazoles as thiatriazolines (114,113 X = S) and thiatriazolidines (115) often as 5-oxides. Recently the so-called non-classical heteropentalenes containing the 1,2,3,5-thia- and -selena-triazole ring system (116) have been prepared. 

A series of MO calculations has been performed on the structure, formation and nucleophilic reactivity of 1,2,3,4-thiatriazoles (1) <76AHC(20)145). However, these calculations have been criticized (see Section 4.28.2.2.3 for a detailed discussion). MO calculations have been carried out for the hypothetical ring closure of thioformyl azide 5-oxide (8 H substituted for Ph) to thiatriazole S-oxide. It is suggested that the variable chemical behavior of thioacyl azides and their S-oxides is due to disruption of the aromatic character of the thiatriazole S-oxide (77T2231). 

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