Cycloaddition reactions ruthenium-catalyzed azide-alkyne

The Ruthenium-Catalyzed Azide-Alkyne Cycloaddition (RuAAC) complements the well-established CuAAC reaction, as the formation of 1,5-substituted triazoles (instead of 1,4-substituted 1,2,3-triazoles) can be achieved with high regioselectivity. In contrast to the CuAAC reaction, triazoles that are synthesized via RuAAC reaction can be formed from terminal as well as internal alkynes. This offers the possibility of the formation of fully-substituted triazoles. 

Ruthenium-Catalyzed Azide-Alkyne Cycloaddition (RuAAC) Click Reactions... 

The regioselective formation of 1,4- and 1,5-disubstituted 1,2,3-triazoles can be accomplished by CuAAC reactions and ruthenium-catalyzed azide-alkyne [3+2] cycloaddition (RuAAC) reactions, respectively [69, 70]. Fokin and coworkers demonstrated that ruthenium complexes such as Cp RuCl(PPh3)2... 

Other metal-mediated reactions of azide reagents to terminal alkynes have also been reported. Indium(ll) triflate catalyzed tandem azidation/l,3-dipolar cycloaddition of various (o,(o-dialkoxyalkynes 134 with trimethylsilyl azide yielded fused 1,2,3-triazoles 135 <05TL8639>. A new ruthenium-catalyzed process for the regioselective synthesis of 1,5-disubstituted-1,2,3-triazoles has been developed <05JA15998>. 

The ruthenium-catalyzed cycloaddition of azides to alkynes to form 1,5-disubstituted triazoles is complimentary to the copper catalyzed route. The Cu(I)-catalyzed reaction is limited to terminal alkynes, and the Ru(II)-catalyzed reaction is active with internal alkynes. 

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