Vinyl azides 1,2,3-triazole derivatives

An intramolecular counterpart of this reaction is the cyclization (Scheme 17) of anions derived from vinyl azides the neutral azides fail to cyclize, presumably because the cyclic tautomer (the triazole) is not aromatic, whereas the anion is. 

Otherwise, 4//-triazole derivatives apparently exist in their open-chain tautomeric forms, as vinyl azides (see Scheme 40). It remains to be shown whether vinyl azides and the isomeric 4/f-triazoles can have independent existence attempts to cyclize vinyl azides have not been successful. ... 

Vinyl sulfones can function as acetylene equivalents through the elimination of sulfinic acid. Reck and coworkers prepared a series of vinyl sulfones for cycloaddition reactions with azides to prepare 1,2,3-triazole derivatives to be incorporated into new oxazolidinone antibacterial agents. Included in the series was the cycloaddition of l-fluoro-l-(phenylsulfonyl)ethylene with the oxizolidinone 156 to give, after elimination of phenylsulfonic acid, a 28% yield of a 1 7 mixture of the regioisomeric 4-and 5-fluorotriazoles (157 and 158) (Fig. 3.91). 

A one-pot sequential and cascade sequence involving the formation of allylic azides, from aryl/heteroaryl/vinyl halides, allene and sodium azide, by palladium catalyzed anion capture, and cyclization-anion capture, followed by 1,3-dipolar cycloaddition provided a variety of 1,2,3-triazoles in good yields <01T7729>. Reaction of a,P-acetylenic aldehydes 107 with sodium azide in dimethylsulfoxide followed by hydrolysis afforded 5-substituted-4-carbaldehyde-1,2,3-triazole derivatives 108 <01TL9117>. 

Scheme 5.34 1,2,3-Triazole derivatives from ring closure of vinyl azides, their anions, or...

The addition of HN3 to nonactivated alkenes with formation of the saturated azides requires drastic conditions and a catalyst. Olefinic double bonds activated by conjugated, electron-withdrawing groups like -CN, -NO2, or -C(0)R react easily [8, 9]. The photolysis [10] and the pyrolysis [7] of HN3 with alkenes yields nitriles, N2, and decomposition products. The reaction of HN3 with alkines usually leads to 1,2,3-triazoles. Single or double addition with formation of vinyl azides or saturated diazides are rare [8, 9]. Arenes and HN3 form aniline derivatives directly and efficiently in the presence of trifluoroacetic acid and the strongly acidic trifluoromethanesulfonic acid [11]. The yield is frequently low in the presence ofH2S04[1]. 

Very few 2/f-triazole syntheses involve azides, apart from those (such as 2-acetyl derivatives) which involve prior formation and rearrangement of IjEf-triazoles. Some vinyl diazides react with triphenyl-phosphine in mild conditions to give iminophosphoranes of 2-amino-triazoles (Scheme 36). ... 

One of the first PEO chemical gels cmistructed through triazole cross-linking was disclosed by HUbom (Scheme 8) [47]. Poly(vinyl alcohol) derivatives with acetylene 25 and azide side chains 26 were prepared and cross-Unked to produce a hydiogelating network 27. For comparative study, a similar type of hydrogelator 29... 

---