Huisgen cycloaddition reaction

The NHCs have been used as ligands of different metal catalysts (i.e. copper, nickel, gold, cobalt, palladium, rhodium) in a wide range of cycloaddition reactions such as [4-1-2] (see Section 5.6), [3h-2], [2h-2h-2] and others. These NHC-metal catalysts have allowed reactions to occur at lower temperature and pressure. Furthermore, some NHC-TM catalysts even promote previously unknown reactions. One of the most popular reactions to generate 1,2,3-triazoles is the 1,3-dipolar Huisgen cycloaddition (reaction between azides and alkynes) [8]. Lately, this [3h-2] cycloaddition reaction has been aided by different [Cu(NHC)JX complexes [9]. The reactions between electron-rich, electron-poor and/or hindered alkynes 16 and azides 17 in the presence of low NHC-copper 18-20 loadings (in some cases even ppm amounts were used) afforded the 1,2,3-triazoles 21 regioselectively (Scheme 5.5 Table 5.2). 

Ramachary, D.B. Barbas, C.R III (2004) Towards Organo-Click Chemistry Development of Organocatalytic Multicomponent Reactions Through Combinations of Aldol, Wittig, Knoevenagel, Michael, Diels-Alder and Huisgen Cycloaddition Reactions. Chemistry A European Journal, 10, 5323-5331. 

H. Isobe, K. Cho, N. Solin, D. B. Werz, P. H. Seeberger, and E. Nakamura, Synthesis of fullerene glycoconjugates via a copper-catalyzed Huisgen cycloaddition reaction, Org. Lett., 9 (2007) 4611-4614. 

Like the 1,3-dipolar Huisgen cycloaddition reaction between azides and acetylenes, thiol-ene chemistry is more than a century old, with the first thiol-alkene addition reaction having been reported by Posner in 1905 [19]. The first thiol-ene... 

Azide end-functionalized polymers have become a major building block in polymer chemistry due to their use in the Huisgen cycloaddition reaction. This reaction involves the reaction of an alkyne with an azide in the presence of a Cu catalyst to form the corresponding 1,3-cydoaddition product. The reaction is considered a dick reaction due to its high efSdency and rdativdy short reaction time. The Huisgen cydoaddition reaction has been used to prepare a variety of end-functionalized polymers starting from the azide end-functionalized polymer. Lutz et was the first to... 

Scheme 27 Huisgen cycloaddition reaction of azide-functionalized polymer prepared with ATRP with various alkynes.

A number of unimolecular alkoxyamines containing alkyne or azide functional groups have also been reported and used in postpolymerization Huisgen cycloaddition reactions. Gungor et reported an alkyne-functionalized... 

R.L. Thompson, K. Damodaran, D. Luebke, H. Nulwala, Aprotic heterocychc anion triazolide ionic liquids—a new class of ionic liquid anion accessed by the Huisgen cycloaddition reaction, Synlett 24 (9) (2013) 1093-1096. 

The reaction between organo-azides and alkynes, called the Huisgen cycloaddition reaction, was reported many years ago [84]. However, intense attention has been given to this reaction only recently. In 2001, the groups of Fokin and Sharpless [85] and Meldal [86] independently discovered that a catalytic amount of Cu(l) drastically increased the reactivity and regioselectivity of the reaction. This discovery sparked intensive efforts on the integration of CuAAC in interdisciplinary research. 

Clark M, Kiser P (2009) In situ crosslinked hydrogels formed using Cu(I)-free Huisgen cycloaddition reaction. Polym Int 58 1190-1195... 

The Huisgen cycloaddition reaction of azides with alkynes to produce triazoles was used to produce HA hydrogels and to encapsulate yeast cells during crosslinking. In this method, azide and alkyne functional groups were installed on HA using EDC chemistry. The hydrogel... 

Cheap, stable, and recyclable heterogeneous CuO nanoparticles and sphereshaped CuO hollow nanoparticles show an excellent catalytic activity in the Huisgen cycloaddition reaction of azides and acetylenes, being compatible with a wide range of functional groups and reaction conditions involving air [48,49]. 

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