Immobilized copper

After the optimization of these conditions, by adding an azide to the input stream it was possible to synthesize a range of substituted triazoles in a heterogeneously catalysed three-component reaction (Scheme 18). After the CFC, the stream was passed through a column containing a resin-immobilized copper-based catalyst, which was used in a previous work by the same authors to successfully catalyze the formation of triazoles from alkynes and azides [44]. An immobilized thiourea-containing cartridge was subsequently used to remove any leached Cu catalyst. In a similar way as for the alkynes production, the series of resins was used to purify the product. 

The electrochemical properties of immobilized copper, zinc superoxide dismutase, and their interaction with super oxide radicals were investigated [474]. 

In another example employing multiple supported catalysts and reagents, Smith et al. (2007a) presented a modular flow reactor in which 14 1,4-disubstituted-l,2,3-triazoles were synthesized. Coupling an immobilized copper(I) iodide species 148 with two scavenger modules (immobilized thiourea 149 and phosphane resin 150), the authors reported the [3 + 2] cycloaddition of an array of azides and terminal acetylene (30 pi min x) to afford the desired 1,4-disubstituted 1,2,3-triazoles (Scheme 40) in moderate to excellent yield (70-93%). 

Zawistowski, J., Weselake, R.J., Blank, G., and Murray, E.D., Fractionation of Jerusalem artichoke phenolase by immobilized copper affinity chromatography, Phytochemistry, 26, 2905-2907, 1987b. 

Krebs JF, Borovik AS (1995) Metallo-network polymers Reversible CO binding to an immobilized copper(I) complex. J Am Chem Soc 117 10593... 

Immobilized copper-zeolite Y (Cu-HY) bis(oxazolines) were employed as heterogeneous catalysts in carbonyl-ene and imino-ene reactions, allowing the synthesis of a-hydroxy and a-amino carbonyl compounds 163 from 161 and 162 in satisfactory yields and high enantioselection <04AG(E)1685>. The use of a new, insoluble polystyrene-bound Box ligand (IPB-BOX) was also described with good activity (85-95% ee) <04TA3233>. 

It is observed that the polymer-immobilized aluminium salts (AITPApva-peg and AITSApva-peg) display higher TON values than the copper ones (CuTPApva-peg and CuTSApva-peg)- The higher TON values of polymer-immobilized aluminium salts could be due to the fact that they have higher acid strength than the corresponding immobilized copper salts. It must be also taken into account... 

It has been shown that organofunctionalized silica surfaces further modified with in situ synthesized copper complexes can be used to produce new stationary phases for HPLC [4]. The immobilized copper complexes provide new sites in the stationary phase that can interact strongly with basic organic compounds. A test mixture of compounds such as benzene, toluene, naphthalene, anthracene, pyrene, and nitrobenzene shows that the presence of copper ion complexes on the modified surface strongly affects the retention factor (fe) of the stationary phases. 

Patwardhan A.V., Goud G.N., Koepsel R.R. and Ataai M.M. 1997. Selection of optimum affinity tags from a phage-displayed peptide library application to immobilized copper (II) affinity chromatography, J. Chromatogr. A, 787, 91. 

SCHEME 337 1,4-Substituted 1,2,3-triazoles synthesis using a silica-immobilized copper-based catalyst. 

The following section deals with comparison study between the three immobilized copper catalysts, cross-linked polymeric material and ionic liquid-supported copper (Cu-CPSIL), imidazolium-loaded Merrifield resin-supported copper (Cu-PSIL), and silica-dispersed CuO (Cu0/Si02) and their application in the one-pot synthesis of l,4-disubstituted-l,2,3-triazoles by the reaction of alkyl halides with sodium azide and terminal alkynes in water at room temperature [36]. 

Silica modified with different functionalities such as -NH2, -SH, diamines, and amino acids is reported to be a good support for various metals like Pd, Cu, Sc, Ru, Pt, and V for different organic transformations [52]. Recently, Likhar et al. [52] reported the A-arylation of N(H)-heterocycles and benzylamines with aryl halides and arylboronic acids using silica immobilized copper complexes (Scheme 12). 

Wang Lei et al. [81] reported the Ar-N coupling of arylboronic acids with imidazoles by using 3-(2-aminoethylamino)propyl functionalized silica gel immobilized copper(II) catalyst (10 mol%) in methanol without any additives and bases. The reactions generated the corresponding cross-coupling products in good yields. Furthermore, silica-supported copper can be recovered and recycled by a simple filtration procedure and used for five consecutive trials without decrease in activity. 

The various types of immobilized copper complexes described in this work aim to eliminate the problems encountered in homogeneous amination of aryl halides. The catalysts displayed good activity and recyclability depending upon the nature of the support. 

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