1.2.3- Triazoles transition metal-catalyzed reactions

There are three common approaches to the displacement of amine substituents from purines. First, diazotization and dediazoniation have been used to replace amine substituents, primarily with hydrogen or hydroxyl, carboxyl, and halide functionalities. Second, the S Ar reactions of quaternary ammonium substituents have provided useful synthetic adjuncts to the displacement reactions of halopurines. Finally, of increasing importance has been the conversion of aminopurines (or oxopurines) to N-linked 1,2,4-triazoles (and other azoles), which function as pseudohalogens and can be displaced by nucleophiles or take part in transition metal-catalyzed reactions. 

Apart from the applications in synthesizing drug molecules with a triazole linkage, azide-alkyne cycloaddition reactions have also been used for various biological applications such as site-specific protein/viruses modifications and functionalization of cell surfaces. Use of transition-metal-catalyzed reactions for... 

In 2010, a methodology for the synthesis of 1,2,3-triazole-fused iso-indolines and dihydroisoquinolines was reported. Starting from easily available terminal allgmes and (2-haloaryl)allq7lazides, the desired products were formed in good to exeellent yields. This method is based on a cycloaddition reaction, via Click chemistry, followed by a transition-metal-catalyzed functionalization of a C-H bond. Later on, a one-pot procedure was reported as well. °... 

To date, copper ions still remain the choice of metal catalyst for the azide-alkyne cycloaddition reaction, which generates 1,4-disubstituted 1,2,3-triazoles as the final product. Chemists have also studied the feasibility of other metals in catalyzing the azide-alkyne cycloaddition. For example, Hein and Fokin surveyed the complexes of all of the first-row transition elements, as well as complexes of Pd(0/II), Pt(II), Au(I/III), and Hg(II) ions, among others. However, none of these metal ions were found to produce triazoles in synthetically useful yields, and the effects of these... 

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