Synthesis click chemistry

Uliniuc A, Popa M, Hamaide T, Dobromir M (2012) New approaches in hydrogel synthesis-click chemistry a review. Cell Chem Technol 46(1-2) 1-11... 

Scheme 18 Click chemistry synthesis of 1,4-disubstituted triazoles...

By combining several click reactions, click chemistry allows for the rapid synthesis of useful new compounds of high complexity and combinatorial libraries. The 2-type reaction of the azide ion with a variety of epoxides to give azido alcohols has been exploited extensively in click chemistry. First of all, azido alcohols can be converted into amino alcohols upon reduction.70 On the other hand, aliphatic azides are quite stable toward a number of other standard organic synthesis conditions (orthogonality), but readily undergo 1,3-dipolar cycloaddition with alkynes. An example of the sequential reactions of... 

The use of click chemistry is a promising strategy as a postsynthetic ligation for nucleic acids in order to circumvent the time-consuming synthesis of phosphoramidites as DNA building blocks [31, 32]. This is particularly relevant for several fluorophores that are unstable under the acidic, oxidative, or basic conditions of automated DNA phosphoramidite chemistry and DNA workup. 

Another example of fluorescence intensity modulation in cou-marins is the 3-azido substitution that quenches the fluorescence completely. These compounds are used as starting material for the synthesis of fluorescent triazolocoumarins by click chemistry [31], Interestingly, the fluorescence of some coumarins depends strongly on the solvent. This is the case for 7-alkoxycoumarins that have been used as probes for microenvironments [32], 7-hydroxycoumarin that is pH sensitive, and 7-NR2 substituted coumarins such as coumarin 120 whose quantum yield is reduced in nonpolar solvents due to a change in the 3D structure [33],... 

This section presents selected examples of the use of zeolites and related porous materials for transformations of carbohydrates, that fall beyond the scope of the previous paragraphs. They include the use of zeolites in click chemistry and in a variety of reactions, including the synthesis of anhydro sugars, cyclization, elimination, and addition reactions to the carbonyl group. 

G. Pourceau, A. Meyer, J.-J. Vasseur, and F. Morvan, Combinatorial and automated synthesis of phosphodiester galactosyl cluster on solid support by click chemistry assisted by microwaves, J. Org. Chem., 73 (2008) 6014—6017. 

Hiki S, Kataoka K (2010) Versatile and selective synthesis of click chemistry compatible heterobifunctional poly(ethylene glycol)s possessing azide and alkyne functionalities. Bioconjug Chem 21 248-254... 

Click chemistry refers to the reaction between an azido functional group and an alkyne to form a [3 + 2] cycloaddition product, a 5-membered triazole ring. This reaction has been used for many years in organic synthesis to form heterocyclic rings. Normally, the click reaction requires high temperatures, and this was the main reason that it was not used as a bioconjugation tool. However, it was discovered that in aqueous solutions and in the presence of Cu(I), the reaction kinetics are dramatically accelerated to provide high yields even at room temperature and ambient pressures (Rostovtsev et al., 2002 Tornoe et al., 2002 Sharpless et al., 2005). 

Figure 7.7 The synthesis of dendrimer molecules using click chemistry proceeds with high yield. Each step results in the cycloaddition reaction between azide-containing molecules and alkyne molecules to form triazole linkages.

Figure 17.12 Azido derivatives of sugars can be used as monomers for glycan and carbohydrate synthesis by cells. Such modifications can be probed using click chemistry or Staudinger ligation reactions.

Sharp less et al. also reported <2001AGE2004> the synthesis of one representative of the present class of compounds. In their studies on click chemistry, the substituted cyclohexyltriazole 302 was prepared, which, upon treatment with a base at reflux temperature, underwent lactonization to yield the fused oxazinone 303 in high yield. 

Li JQ, Hu MY, Yao SQ (2009) Rapid synthesis, screening, and identification of xanthone-and xanthene-based fluorophores using click chemistry. Org Lett 11 3008-3011... 

Scheme 7.1 Click chemistry synthesis of 1,4-disubstituted-l,2,3-triazoles by a 1,3-dipolar cycloaddition reaction of organic azides with terminal acetylenes.

Finally, Lecomte and coworkers reported the synthesis of mikto-arm star-shaped aliphatic polyesters by implementing a strategy based on click chemistry (Fig. 36) [162]. Firstly, the polymerization of sCL was initiated by a diol bearing an alkyne function. The chain-ends were protected from any further undesired reaction by the esterification reaction with acetyl chloride. The alkyne was then reacted with 3-azidopropan-l-ol. The hydroxyl function located at the middle of the chain was then used to initiate the ROP of sCL and y-bromo-s-caprolactone. Finally, pendant bromides were reacted successfully with sodium azide and then with N, N-dimethylprop-2-yn-l-amine to obtain pendant amines. Under acidic conditions, pendant amines were protonated and the polymer turned out to exhibit amphiphilic properties. 

Figure 7.18 Representative in situ Click chemistry reaction analysis by HPLC-SIM-MS the triazole product is indicated by the dashed line, (a) Triazole products obtained by conventional synthesis with Cu(l) catalysis, (b)-(d) Microfuidic device reactions performed at 37 °C for 40 h (b) in the presence of CA II, (c) in the presence ofCA II and potent CA inhibitor to block the CA active site and (d) in the absence of CA II. (e) Reaction performed at 37° C for 40 h in microtitre plate. Reproduced with permission from Wang,., Sui, C., Mocharla, V.P., Lin, R.J., Phelps, M.E., Kolb, H.C. and Tseng, H.-R., Integrated microfluidics for parallel screening of an in situ click chemistry library. Angewandte Chemie International Edition 2006, 45, 5276-5281. Copyright Wiley-VCH Verlag GmbH.

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. 

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