Properties of 1,2,3,4-Thiatriazoles

The nitrogen formed was analyzed by mass spectrometry and found to contain 96.4% of 15N14N, corresponding to 98.8% loss of nitrogen from the N-2 and N-3 positions [Eq. (2)]. 

Possible participation of an intermediate, such as a three-membered ring compound (thiazirine), was briefly discussed. 

The kinetics of the decomposition of 5-alkoxythiatriazoles in dibutyl phthalate solution was studied by Jensen et al.16 The reaction was followed by manometric measurement of the nitrogen evolved and follows first-order kinetics. Rates of decomposition and activation parameters are shown in Table I. 

The activation energies for the different alkoxythiatriazoles differ very little, in agreement with the idea that the reaction proceeds via the same mechanism in all cases. The decomposition of alkoxythiatriazoles is analogous to the decomposition of 5-alkylthiatriazoles,17 in which 

The thioazide must decompose rapidly since the characteristic azide band near 2130 cm-1 was not observed in the IR spectrum of a decomposing thiatriazole. 

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While the neutral 1,2,3,4-oxatriazoles (1) still await synthesis, some of their properties have been predicted by theoretical calculations. AMI calculations combined with a principal component analysis loading data from other related heteroaromatics have been used to estimate geometric characteristics, aromaticity, energy of formation, and N chemical shifts <90JPR885>. The oxatriazoles (1) and (7) and the 1,2,3,5-thiatriazoles, which also have not been prepared, are calculated to be in the group with the lowest classical and magnetic aromaticity. 

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). 

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