Calix arenes catalysis

Calix[ ]arenes are a family of macrocycles prepared by condensation reactions between n /v/ra-substituted phenols and n formaldehyde molecules under either base or acid catalysis. Different sizes of the macrocycles can be obtained (n = 4-20) (Stewart and Gutsche, 1999) depending on the exact experimental conditions, which were mastered in the 1960 s (Gutsche, 1998), but the most common receptors are those with n =4,6,8 (macrocycles with an odd number of phenol units are more difficult to synthesize). We use here the simplified nomenclature in which the number of phenolic units is indicated between square brackets and para substituents are listed first.4 Calixarenes, which can be easily derivatized both on the para positions of the phenolic units and on the hydroxyl groups, have been primarily developed for catalytic processes and as biomimics, but it was soon realized that they can also easily encapsulate metal ions and the first complexes with d-transition metal ions were isolated in the mid-1980 s (Olmstead et al., 1985). Jack Harrowfield characterized the first lanthanide complex with a calixarene in 1987, a bimetallic europium complex with p-terf-butylcalix[8]arene (Furphy etal., 1987). 

Supramolecular catalysis may also involve the combination of a host cavity and a metal active site as in the bis(diphenylphosphino)calix[4]arene nickel(II) complex 12.40 which acts as an efficient catalyst for ethylene and propylene polymerisation, and in tandem with zirconocene dichloride, for the formation of linear low-density polyethylene. In the latter case the complex gives very little branching - a significant advantage. The key to the effectiveness of the catalyst involves calixarene-induced changes in the bite angle at the Ni(II) centre, which is square planar in the active form of the catalyst.29... 

Semeril, D., Lejeune, M., Matt, D., Calix [4] arene-derived nickel diphosphine complexes for LLDPE synthesis via orthogonal tandem and one-pot catalysis. NewJ Chem. 2007, 31, 502-505. 

The calix[4]arene-based diphosphine (119) (R = Me, Pb, Ph R = Pb) on reaction with [Rh(/r-Cl)(COD)]2 and then TlPFg forms the dinuclear species (120). These were tested as catalysts for hex-l-ene hydroformylation (see Carbonylation Processes by Homogeneous Catalysis) and that with R = Ph was best, but the performance was not better than extant systems and no special role for the calixarene moieties could be discerned. Several papers have used DFT calculations as part of QM/MM studies (see Molecular Orbital Theory) to probe the course of the hydroformylation process (see Carbonylation Processes... 

Plots of EM vs. the carboxylate-carbonyl distances in the ester substrates, taken as a gross measure of their size, are shown in Figure 8.1. It is apparent that the dinuclear catalyst 14-Ba2, in which the azacrown units are linked to vicinal positions of the calix[4] arene scaffold, is not only far superior to its diagonal regioisomer 15-Ba2 in all cases, but it is also superior to 16-Ba2 in the reactions of esters 18-20. The EM profile shows that the catalytic efficiency of 14-Ba2 reaches its maximum value in the reaction of ester 19, and drops to a very low value in the reaction of the longest ester 21. This indicates that 14-Ba2 cannot expand its intermetal distance to fit the long carboxylate-carbonyl distance in 21. In conclusion, reactivity data obtained for the various catalyst-substrate combinations indeed show that a close fit of ester size to metal-to-metal distance is an important prerequisite for catalysis. However, the marked superiority of 14-Ba2 over... 

Efficient catalysis of HPNP transesterification (Equation 8.10) arising from synergic action of the two metal centres was reported in previous studies for the dinuclear zinc(II) complex of DAMP functionalized calix[4]arene 25. In marked contrast to what observed on the catalytic cleavage of esters (Table 8.2), the 1,2-vicinal complex 24-Zn2 was subsequently found to be significantly less effective than its 1,3-distal regioisomer 25-Zn2. 

R. Cacciapaglia, A. Casnati, L. Mandolini, D. N. Reinhoudt, R. Salvio, A. Sartori, R. Ungaro, Catalysis of diribonucleoside monophosphate cleavage by water soluble copper(II) complexes of calix[4]arene based nitrogen ligands, J. Am. Chem. Soc., 2006, 128, 12322-12330. 

Similar to calix[n]arenes, porphyrins have been known to be one of the support pillars of supramolecular chemistry attributing suitable photoactive and electroactive properties to the molecular structures designed around them for building artificial molecular devices. Thus, various metallated and free base porphyrin-calixarene assemblies could afford attractive scaffolds for application in the areas of multipoint molecular recognition, receptors, host-guest chemistry, catalysis and photoinduced electron transfers. 

Asfari, Z. Thuery, P. Nierlich, M. Vicens. J. Unsym-metrical calix[4]- /5-crowns-6 with unequivalent crown loops. Tetrahedron Lett. 1999. 40. 499-502. van Axel Castelli. V. Cort, A.D. Mandoliai. L. Rein-houdt, D.N. Schiaffino. L. Catalysis of the addition of benzenethiol to 2-cyclohexen-I-ones by uranyl-salophen complexes A catalytic metallocleft with high substrate specificity. Chem. Eur. J. 2000, 6. 1193-1198. Albrecht, M. Hovestad, N.J. Boersma, J. van Koten. G. Multiple use of soluble rnetallodendritic materials as catalysts and dyes. Chem. Eur. J. 2001, 7. 1289-1294. Haino. T. Araki. H. Yamanaka. Y. Fukazawa, Y. Fullerene receptor based on calix[5]arene through metal-assisted self-assembly. Tetrahedron Lett. 2001. 42, 3203-3206. 

Khiri N, Bertrand E, Ondel-Eymin M-J, Rousselin Y, Bayardon J, Harvey PD, Juge S (2010) Enantioselective hydrogenation catalysis aided by a a-bonded calix[4]arene to a F-chirogenic aminophosphane phosphinite rhodium complex. Organometallics 29 3622-3631... 

Calix[n]arenes in action Useful host—guest catalysis in organic chemistry 12COC949. 

Shinkai and coworkers [8] have prepared the water soluble hexasulfonate of calix[6]arene and have shown that it enhances the rate of the acid-catalyzed addition of water to A/ -benzyldihydronicotinamide. With the water soluble carboxy calixarenes now available by the procedure described in Section 2 it is of interest to compare these with the sulfonate and also to ascertain the effect of ring size on the catalysis. The observed rates of hydration, the values of the catalytic constant... 

Le Clainche L, Rondelez Y, Sen que O, Blanchard S, Campion M, Giorgi M, Duprat E, Le Mest Y, Reinaud O. Calix[6]arene-based models for mono-copper enzymes a promising supramolecular system for oxidation catalysis. CR Acad Sci 2000 3(10) 811-9. 

Seitz J, Maas G. Calixarenes as ligands for transition-metal catalysis a bis(calix[4]arene-11,23-dicarboxylato) dirhodium complex. Chem Commun 2002 4 338-9. 

Erdemir, S., and M. Yilmaz. 2009. Synthesis of Calix[N]Arene-Based Silica Polymers for Lipase Immobilization. Journal of Molecular Catalysis B Enzymatic 58 (1-4) 29-35. 

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