Polymer-supported copper catalyst

Islam, S. M., Mondal, S., Mondal, R, Roy, A. S., Tuhina, K., Salam, N., and Mobarak, M. 2012. A rensable polymer supported copper catalyst for the C-N and C—O bond cross-couphng reaction of aryl halides as well as arylboronic acids. J. Organometal. Chem. 696(26) 4264-4274. 

Polymer-supported copper catalyst (A21-Cul) was successfully applied for fhe synthesis of 1,2,3-triazoles 97 using aqueous PEG 4(30 as a solvent (Scheme 53) [82]. The catalyst and solvent were reused up to four times without substantial decrease of yield (85-87%), however, at the fifth cycle the yield dropped to 67%. 

L. Wang, C. Cai, Reusable polymer-supported copper catalyst for one-pot synthesis of 1-aUtyl- and l-aryl-l,2,3-triazoles green, simple, and effective. Green Chem. Lett. Rev. 3 (2010) 121-125. 

Chan, T. R. and Fokin, V. V. 2007. Polymer-supported copper(I) catalysts for the experimentally simplified azide-alkyne cycloaddition. QSAR Comb. Sci. 26(11-12) 1274-1279. 

The palladium-catalyzed, microwave-assisted conversion of 3-bromopyridine to 3-cyanopyridine using zinc cyanide in dimethylformamide (DMF) has been reported <2000JOC7984>. Substoichiometric quantities of copper or zinc species improve both conversion rate and efficiency of Pd-catalyzed cyanation reactions <1998JOC8224>. A modification of this procedure uses a heterogeneous catalyst prepared from a polymer-supported triphenylphosphine resin and Pd(OAc)2 the nitriles were obtained from halopyridines in high yields <2004TL8895>. The successful cyanation of 3-chloropyridine is observed with potassium cyanide in the presence of palladium catalysts and tetramethylethylenediamine (TMEDA) as a co-catalyst <2001TL6707>. 

Polymer-supported benzenesulfonyl azides have been developed as a safe diazotransfer reagent. ° These compounds, including CH2N2 and other diazoalkanes, react with metals or metal salts (copper, paUadium, and rhodium are most commonly used) to give the carbene complexes that add CRR to double bonds. Diazoketones and diazoesters with alkenes to give the cyclopropane derivative, usually with a transition-metal catalyst, such as a copper complex. The ruthenium catalyst reaction of diazoesters with an alkyne give a cyclopropene. An X-ray structure of an osmium catalyst intermediate has been determined. Electron-rich alkenes react faster than simple alkenes. ... 

Analysis of the cmde product after the first run showed a contamination of ca. 850 ppm of palladium. At the same time the polymer-supported catalyst contained up to 3 % of copper. Thus, a copper-palladium exchange led to the observed decrease of the catalyst activity. 

The applications reported for polymer-supported, soluble oxidation catalysts are the use of poly(vinylbenzyl)trimethylammonium chloride for the autooxidation of 2,6-di-tert-butylphenol [8], of copper polyaniline nanocomposites for the Wacker oxidation reaction [9], of cationic polymers containing cobalt(II) phthalocyanate for the autooxidation of 2-mercaptoethanol [10] and oxidation of olefins [11], of polymer-bound phthalocyanines for oxidative decomposition of polychlorophenols [12], and of a norbornene-based polymer with polymer-fixed manganese(IV) complexes for the catalytic oxidation of alkanes [13], Noncatalytic processes can also be found, such as the use of soluble polystyrene-based sulfoxide reagents for Swern oxidation [14], The reactions listed above will be described in more detail in the following paragraphs. 

At the same time, Cozzi described the immobilization of Box ligands on PEG polymer (polymer 99, Scheme 49), and the corresponding copper catalyst used for the cyclopropanation reaction was also involved in Diels-Alder cycloaddition between cyclopentadiene and/V-acryloyloxazolidinone (Scheme 54) [95]. This reaction was performed with 15 mol% each of Box ligand and Cu(OTf)2 in DMF in order to obtain homogeneous conditions. The reaction occurred in good yield (up to 83%) and excellent diastereoselectivity in favour of the endo stereoisomer (ratio endo/exo >98/2). However, the maximum of enantioselectivity was only 45% contraiy to the non-supported Box equivalent catalyst which led to complete end at 95% ee and 88% yield. 

Portnoy focused his attention on the immobilization of PyBox ligands [153], The polymer-supported PyBox 240 were prepared in five steps from the Wang trichloroacetamidate resin (Scheme 96). The supported-ligands 240 were allowed to react with copper (1) triflate for 24h to afford the corresponding catalysts 241. These catalysts were then used in the first heterogeneous catalyzed addition of phenylacetylene to imine. 

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