Alkyne-azide cycloaddition

Besides short ELPS, longer ELPs have also been conjugated to synthetic polymers. In one approach, Cu(I)-catalyzed azide-alkyne cycloaddition click chemistry was applied. For this purpose, ELPs were functionalized with azides or alkynes via incorporation of azidohomoalanine and homopropargyl glycine, respectively, using residue-specific replacement of methionine in ELP via bacterial expression [133]. More recently, an alternative way to site-selectively introduce azides into ELPs was developed. Here, an aqueous diazotransfer reaction was performed directly onto ELP[V5L2G3-90] using imidazole-1-sulfonyl azide [134]. 

Gramlich PME, Wirges CT, Manetto A, Carell T (2008) Postsynthetic DNA modification through the copper-catalyzed azide-alkyne cycloaddition reaction. Angew Chem Int Ed... 

A variety of triazole-based monophosphines (ClickPhos) 141 have been prepared via efficient 1,3-dipolar cycloaddition of readily available azides and acetylenes and their palladium complexes provided excellent yields in the amination reactions and Suzuki-Miyaura coupling reactions of unactivated aryl chlorides <06JOC3928>. A novel P,N-type ligand family (ClickPhine) is easily accessible using the Cu(I)-catalyzed azide-alkyne cycloaddition reaction and was tested in palladium-catalyzed allylic alkylation reactions <06OL3227>. Novel chiral ligands, (S)-(+)-l-substituted aryl-4-(l-phenyl) ethylformamido-5-amino-1,2,3-triazoles 142,... 

M. Meldal and C. W. Tomqe, Cu-catalyzed azide-alkyne cycloaddition, Chem. Rev., 108 (2008) 2952-3015. 

Agard, N.J., Prcschcr, J.A., and Bertozzi, C.R. (2004) A strain-promoted [3+2] azide-alkyne cycloaddition for covalent modification of biomolecules in living systems. /. Am. Chem. Soc. 126, 15046-15047. 

Sun, X.-L., Stabler, C.L., Cazalis, C.S., and Chaikof, E.L. (2006) Carbohydrate and protein immobilization onto solid surfaces by sequential diels-alder and azide-alkyne cycloadditions. Bioconjugate Chem. 17, 52-57. 

CuO nanostructures of variable shapes CuO nanospheres (5-10 run), CuO nanorods (WXL = 24-27 nmxl24-140 run) and CuO nanowires (WXL= 8-10 nmx230-270 nm) have been synthesised to study the effect of shape of the catalyst on the Cu(I)-catalyzed click azide-alkyne cycloaddition. Cu(I) species were generated in situ by the reduction of CuO nanostructures in the presence of sodium... 

Keywords Azide-alkyne cycloaddition, triazoles, CuO-nanowires, CuO-nanorods, CuO-nanospheres Reference ... 

Fused triazoles were synthesized in a similar manner through the Huisgen azide-alkyne cycloaddition, which was carried out by simple heating the Ugi adducts at 100°C. Five different fused triazole scaffolds 160-164 were obtained by placing the additional functions in different components or changing the distance between them and the Ugi-reacting group [131]. 

Another approach for the synthesis of networks relies on the polycondensation of multifunctionalized polyesters with the appropriate multifunctionalized agent, provided that one of the partner is at least tri-functionalized. Toward this end, several reaction have been reported, such as the Michael addition of amines onto acrylates [184], the coupling of ketones and oxyamines [185], the click copper(II)-catalyzed azide-alkyne cycloaddition [186], and esterification reactions [25, 159, 187]. Interestingly, if esterification reactions are used, the crosslinks are then degradable. 

The reaction chosen to connect the tethers in situ was the Huisgen azide-alkyne cycloaddition (Scheme 10.5). The Huisgen cycloaddition forms 1,2,3-triazoles as a nearly 1 1 mixture of regioisomers (10.28 and 10.29). The reaction is slow at room temperature. However, if the azide and alkyne are positioned ideally, such as when bound in close proximity by AChE, then the reaction occurs at room temperature. 

Diaz, D.D., Punna, S., Holzer, P., Mcpherson, A.K., Sharpless, K.B., Fokin, V.V. and Finn, M.G. (2004) Click chemistry in materials synthesis. 1. Adhesive polymers from copper-catalyzed azide-alkyne cycloaddition. J. Polym. Sci. Polym. Chem., 42, 4392. 

Copper(I)-catalyzed azide-alkyne cycloaddition as a selective bioconjugation technique... 

Beatty KE, Fisk JD, Smart BP et al (2010) Live-cell imaging of cellular proteins by a strain-promoted azide-alkyne cycloaddition. Chembiochem 11 2092-2095... 

A copper catalysed click (azide-alkyne cycloaddition) reaction has been used to prepare a fluorous-tagged TEMPO catalyst (Figure 7.20). TEMPO is a stable organic free radical that can be used in a range of processes. In this case, its use in metal-free catalytic oxidation of primary alcohols to aldehydes using bleach as the terminal oxidant was demonstrated. The modified TEMPO can be sequestered at the end of the reaction on silica gel 60 and then released using ethyl acetate for reuse in further reactions in this way the TEMPO was used four times with no loss in activity. 

Rodionov VO, Fokin VV, Finn MG. Mechanism of the ligand-free Cu-I-catalyzed azide-alkyne cycloaddition reaction. Angew. Chem. Int. Ed. 2005 44 2210-2215. 

Key words Liposome, Azide-alkyne cycloaddition, Bioconjugation chemistry. Click chemistry. 

CavalK S, Tipton AR, Overhand M, Kros A (2006) The chemical modification of Hpo-some smfaces via a copper-mediated [3-t2] azide-alkyne cycloaddition monitored by a colorimetric assay. Chem Commim (Camb) 3 0 3193-3195... 

Lewis WG, Magallon EG, Eokin W, Finn MG (2004) Discovery and characterization of catalysts for azide-alkyne cycloaddition by fluorescence quenching. J Am Chem Soc 126 9152-9153... 

Catalytic azide-alkyne cycloaddition reactivity and applications , Wu, P. and Fokin, V. V., Aldrichimica Acta, 2007, 40, 7. 

Solid-phase Cu(l) catalyzed azide-alkyne cycloadditions have also proven to be a rehable and highly robust procedure [6,25-27]. Both the azide and the alkyne functions have been incorporated into different resins. These functionaUzed supports have been appUed to the synthesis of triazole- and non-triazole-containing products by using, in the latter case, the triazole functionaUty as a hnker. The cycloadditions proceed easily on the solid phase showing more sensitivity to steric factors than in solution phase and little sensitivity to reaction conditions, resin type, or subsequent transformations. The Cu(II) reduction protocol, as well as the use of Cu(I) salts, work with equal efficiency in various organic solvents (THF, DMF, acetonitrile, DMSO). 

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