Alkyl- or Aryl-Trisubstituted 1,2,3-Triazoles

Comparatively few 1,2,3-triazoles bearing three carbon substituents have been prepared, and the general methods found in Chapters 1 and 2 have been applied as in the direct addition of azides to acetylenes. Some questions, such as the effect of an oitho-substituent in an aryl azide, which can greatly alter the product yield, deserve more attention (Eq. 1). Compound 

1-1 also represents a successful approach to controling mono- or diaddition to alkadiynes. 

Many azides have been added to diphenylacetylene, but the report of 95% yield with benzyl azide offers what may well be optimal conditions. High yields have also been obtained from l,4-but-2-ynediol (3.1-2) and the exciting bisacetal (3.1-3) with a variety of azides (Eqs. 2,3). A recent note describing the preparation of fluorinated acetylenes included an example of 

The addition of heteroaromatics takes place in somewhat better, although still only fair, yield (Eq. 6). A radically different approach to the synthesis of similar compounds deserves greater elaboration (Eq. 1) The fact that yields for only the second step are given make the attractiveness of this method hard to evaluate. 

The formation of relatively unstable amino-1,2,3-triazolines (3.1 7) from enamines is another traditional route employed for trisubstituted 1,2,3-triazole synthesis. Munk and Kim demonstrated the great regiospecificity of such reactions (Eq. 8). Pocar and his collaborators have extended the use of enamines, including the following examples (Eqs. 9,10). - An especially interesting example involves an acid-catalyzed rearrangement (Eq. 11).  

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