Derivatives of 1,2,3-Triazole

Triazolopyrimidines and their derivatives are relatively stable toward alkaline and acid hydrolysis. However, the action of aqueous sodium hydroxide, ammonia, or hydrazine under pressure converts them to derivatives of 1,2,3-triazole. ... 

In NMR speetra of trialkyltin derivatives of 1,2,3-triazoles, C(4) and C(5) atoms show one eommon signal at the lowest attained temperature of solution, -50°C [77JOM(132)69]. This observation was explained by the symmetrie strueture 42c of the eompounds (R = COOMe) [77JOM(127)273]. However, rapid annular tautomerism explains this observation equally well and eannot be ruled out. 

The first 1,2,4-triazoles were prepd in 1885 by J.A. Bladin (Ber 18), who did considerable work in the investigation of this class of compd H. vonPechmann published a paper in 1888 in which he described the prepn of some derivatives of 1,2,3-triazoles and proposed naming them Osotriazones because they were prepd from osazone . This name, was changed in 1891 by vonPechmann to osotriazole . A. Andreocci also investigated triazoles, and in 1889 and 1894 published papers in which he called some of them Pyrrodiazoles . All of these compds are now called triazoles ... 

As the number of nitrogen heteroatoms increases, the stability of lithium azoles decreases the 5-lithio derivatives of 1,2,3-triazoles 778 ring-open spontaneously. l-Methyltetrazol-5-yllithium decomposes to nitrogen and lithium methyl-cyanamide above 50 G, although it gives the expected Grignard-like reactions with bromocyanogen, esters, ketones, and sulfur at lower temperatures. 

Hoover and Day. In this, the triazole is stirred with liquid ammonia while small pieces of sodium are added until a faint blue color persists. This color is discharged with a little ammonium chloride, and the solvent is allowed to evaporate overnight. After the toluene formed in the reaction has been removed under vacuum, the remaining white sodium salt is dissolved in a little ice water. The highly alkaline solution is acidified with hydrochloric acid and the product filtered. In this way, these authors debenzylated the 4-amino-3-benzyl derivatives of 1,2,3-triazole (37%), and its 5-carboxamide (66%), 5-carboxyhydrazide (50%), and 5-nitrile (86% yields) (56JA5832). 

The course and orientation of 1,3-cycloadditions will be illustrated by listing examples of actual reactions. Most dipolarophiles have carbon-carbon unsaturated bonds, and give derivatives of 1,2,3-triazole, pyrazole, isoxazole and pyrrole according to the following reactions (unless otherwise indicated, reference is made to monosubstituted dipolarophiles olefins and acetylenes usually, but not always, behave similarly) ... 

To conclude this section just a quick word about triazolium cation derivatives of 1,2,3-triazoles [87]. They have also been investigated and show application for functional ionic liquids and precursors of mesoionic carbenes for catalytic purposes, or as units of supramolecular assemblies and molecular machines. 

The direct incorporation of a fluorine atom in the ring essentially affects versatile physicochemical and chemical characteristics of the heterocyclic system, in particular, its tautomerism, dipole moment, and the acid-base properties. For instance, tautomeric equilibria involving NH-unsubstituted fluoro derivatives of 1,2,3-triazoles [22, 23], 1,2,4-triazoles [24], and tetrazoles [25-28] were explored in a series of theoretical studies. The acid-base properties of these heterocycles (in particular, the CH-acidity of some among them) were also studied [28-30]. These investigations showed that the fluorine atom attached to the heterocyclic system changed significantly the character of the electron density distribution and consequently the polarity of the heterocycle, strongly increased its acidity and decreased its basicity. 

Dipolar cycloaddition of flnoroalkyl azides to acetylenes in the version of the click-chemistry involving the above mentioned catalytic system (CUSO4 5H2O -sodium ascorbate) essentially extended the set of the known flnoroalkyl derivatives of 1,2,3-triazole some 1,2,3-triazole derivatives pievionsly regarded as exotic became relatively accessible. Read et al. recently reported on the results of research of the effect on the m-xylene surface tension of the additives of exotic surfactants based on flnoroalkyl derivatives of 1,2,3-triazoles, e.g., compound 50 [50]. The synthesis of fluoroalkyl-l,2,3-triazoles using the above mentioned procedure was also described in the earlier publication of the same team [51]. 

Read et al. synthesized surface-active derivatives of 1,2,3-triazole 49,50 containing at the nitrogen atom perfluoroalkyl (lipophilic) substituents, and at the carbon atom perfluoroalkoxy or alkoxy (hydrophilic) groups. It is significant that the surfactant properties of these compounds can be purposefully regulated varying the length of the fluoroalkyl chain [49, 50],... 

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