Recyclable catalytic systems

Iridium nanoparticles generated in l-n-butyl-3-methylimidazolium (BMI)-based ionic liquids were found to be excellent recyclable catalytic systems for the hydrogenation of a variety of substrates, including ketones such as simple ketones. The Ir nanoparticles were prepared by simple reduchon of [Ir(cod)Cl]2 dispersed in BMI-PFis at 75 °C under 4 atm of H2. Benzaldehyde, cyclopentanone, methyl butanone and derivatives were hydrogenated with almost complete conversion, with TOFs ranging from 17 to 96h under solventless conditions (substrate Ir ratio = 250, 75 °C, 4 atm FI2) [102]. 

The calcined iron-grafted materials exhibit high selectivity as catalysts for oxidations of alkanes, alkenes and arenes with H2O2 as the oxidants [13a]. A similar method has been used by Tilley et al. to prepare a pseudotetrahedral (Co(II) [Co(4,4 -di Bu-bipy) OSi(0 Bu)3 2]) complex grafted onto the SBA-15 surface and subsequently use it in catalytic oxidation of alkylaromatic substrates with tert-butyl hydroperoxide [14]. Unfortunately, neither iron nor cobalt surface organometaUic compounds have been tested in the recycled catalytic system. 

Gmouh, S., Yang, H., Vaultier, M. Activation of Bismuth(lll) Derivatives in Ionic Liquids Novel and Recyclable Catalytic Systems for Friedel-... 

Yadav, J. S., Reddy, B. V. S., Bhaishya, G. lnBr3-[bmim]PF6 a novel and recyclable catalytic system for the synthesis of 1,3-dioxane derivatives. Green Chem. 2003, 5, 264-266. 

Song s group [25] has developed a novel and recyclable catalytic system for Friedel-Crafts alkylation of aromatic compounds with alkenes. The Sc(OTf)j was immobilized in the ionic Uquids, to obtain quantitatively the desired alkylated products in the reaction of Ihe allqrlation of benzene with hex-l-ene, in which the ionic liquids containing 20 mol% ScCOTl) such as [EMIM][SbFg] ([EMIM] is denoted as... 

Gmouh S, Yang H, Vaultier M (2003) Activation of bismuth(lll) derivatives in ionic hquids novel and recyclable catalytic systems for Friedel-Crafts acylahon of aromahc compounds. Org Lett 5(13) 2219-2222... 

Chary MV, KeerthysriNC,VupallapatiSVN,LigaiahN,KantevariS(2008)Tetrabutylammomum bromide (TBAB) in isopropanol an efficient, novel, neutial tmd recyclable catalytic system for the synthesis of 2,4,5-trisubstituted imidazoles. Catal Commun 9 2013-2017... 

Yadav, J.S., Reddy, B.V.S., Gayathri, K.U. and Prasad, A.R. (2002) Scandium triflate immobilized in ionic liquids A novel and recyclable catalytic system for hetero-Diels-Alder reactions. Synthesis-Stuttgart, 17, 2537-2541. 

The treatment of an IL covalently bound to a silica surface (Figure 12) with a classical imidazolium IL ([G4GiIm]PF6 and [G4GiIm]BF4) results in the formation of a multiple layer of free IL on the support. Rhodium complexes such as [RhH(GO)(TPPTS)3] immobilized in these systems generate a robust and recyclable catalytic system for the hydroformylation of 1-hexene. 

Zhang J, Zhang M, Tang K, Verpoort P, Sun T (2014) Polymer-based stimuli-responsive recyclable catalytic systems for organic synthesis. Small 10 32... 

Recently, polystyrene-supported pyrrole-2-carbohydrazide (PSP) was combined with Cu(l) to make up a recyclable catalytic system (Cu(l)/PSP) for the N-(hetero)ary-lation of amines and imidazole (Huang et al., 2013). This heterogeneous catalyst could also be successfully applied to the assembly of imidazo[l,2-a]quinoxaline through the intramolecular cyclization of A -(2-iodophenyl)-l//-imidazole-2-carboxamide (Scheme 4.39). 

In this homogeneous and recyclable catalytic system, after the reaction end, hexane is added to the system, the upside comprises the ethyl esters and the downside containing the aqueous/ethyl alcohol phase. It was possible because the hexane and aqueous/ethyl alcohol phase are immiscible at room temperature. Consequently, the catalyst (i.e. HPW or SnCl2 as convenient) remains in the polar phase and may be then collected as a solid after remove via evaporation both alcohol and water (Figure 10). 

Further developments concerning the Stille cross-coupling methodology of alkynylstannanes avoided the use of Pd-based catalysts by utilizing a combination of CU2O nanoparticles, P(o-Tol)3, KF, and TBAB (tetrabutylammonium bromide) as a recyclable catalytic system [252]. Coupling of aryl iodides and activated aryl... 

Michael Addition of -Keto Esters to Unsaturated Carbonyl Compounds. The conjugate addition of 18-keto esters to a. S-unsaturated ketones can be effected using 10 mol % copper(n) triflate immobilized in an ionic liquid ([BM1M][BF4]), as a recyclable catalytic system (eq 38). ... 

Effort has also been made on the development of recyclable catalytic systems. For example, CuO nanoparticles [101,102], Cu-SiO [103], Cu-SiOj-bipyridyl [104], and CuFe O nanoparticles [105] have been investigated for the coupling of aryl halides with phenols. 

Chandrasekhar S, Reddy NK et al (2010) Oxidation of alkynes using PdClj/CuClj in PEG as a recyclable catalytic system one-pot synthesis of quinoxalines. Tetrahedron Lett 51 3623-3625... 

Kaboudin B, Mostafalu R, Yokomatsu T (2013) FejO nanoparticle-supported Cu(ll)-p-cyclodextrin complex as a magnetically recoverable and reusable catalyst for the synthesis of symmetrical biaryls and 1,2,3-triazoles from aryl boronic acids. Green Chem 15 2266-2274 Roy S, Chatteijee T, Islam SM (2013) Polymer anchored Cu(II) complex an efficient and recyclable catalytic system for the one-pot synthesis of 1,4-disubstituted 1,2,3-triazoles starting from anilines in water. Green Chem 15 2532-2539... 

Roberta B, Antonietta C, Giancarlo F, Antonella G (2003) CHjReOj/HjOj in room temperature ionic liquids an homogeneous recyclable catalytic system for the Baeyer-Villiger reae-tion. Tetrahedron Lett 44 8991-8994... 

Puentes MA, MunozBK, Jacob K, etal. Functionalization ofnon-activated C-H bonds of alkanes an effective and recyclable catalytic system based on fluorinated silver catalysts and solvents. Chem EurJ. 2013 19 1327-1334. 

Ding, Y., Zhao, W., Zhang, Y, et al. (2011). An Effective and Recyclable Catalytic System for Alcohol Oxidation in Water Based on a Temperatnre-Responsive Catalyst, Reac. Kinet. Mech. Cat., 102, pp. 85-92. 

A. Kumar, S. Aerry, A. Saxena, A. De, S. Mozumdar, Copper nanoparticulates in guar-gum a recyclable catalytic system for the Huisgen [3 + 2]-cycloaddition of azides and alkynes without additives under ambient conditions. Green Chem. 14 (2012) 1298-1301. 

Selective hydrogenolysis of cyclic and linear ether C-O bonds is another very important step reaction in the treatment of the biomass and requires stable and recyclable catalytic systems. 

Several methods can be used to achieve recyclable catalytic systems, such as the following ones (i) utilization of heterogeneous sofid catalytic materials (ii) formation of dispersed nano-, sol-gel, and micellar systems (iii) phase division, where a homogeneous catalyst and substrate are usually well soluble in one solvent, while the product is soluble in another solvent,... 

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