Alkene epoxidations catalysed by Mo(VI) supported on Merrifield's polymer

Gil, Salvador; González, R. Rubio; Mestres, R.; Sanz, Vicente Claramonte; Zapater, A

doi:10.1016/s1381-5148(98)00056-x

Cited by 19 publications

(3 citation statements)

References 6 publications

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“…We used the chloromethylated polystyrene crosslinked with 2% DVB as the support mainly owing to its superior flexibility, which is known to facilitate the grafting of metallic atoms via polymer anchored ligands. 9b, 28 The amino acid containing polymer was subsequently allowed to react with the peroxomolybdenum species generated in situ by Scheme 1 Synthesis of Merrifield resin supported pMo complexes. (A) Proposed structure of polymer anchored compounds.…”

Section: Synthesis and Characterizationmentioning

confidence: 99%

Merrifield resin supported peroxomolybdenum(vi) compounds: recoverable heterogeneous catalysts for the efficient, selective and mild oxidation of organic sulfides with H2O2

et al. 2013

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We have generated new heterogeneous catalysts by immobilizing dioxomonoperoxomolybdenum(VI) on amino acid functionalized Merrifield resin, which exhibit excellent activity, stability and selectivity for the oxidation of thioethers and dibenzothiophene (DBT) to the corresponding sulfoxides or sulfones by H 2 O 2 at ambient temperature. The synthetic protocols are high-yielding, halogen-free, environmentally clean and safe, and operationally simple. The catalysts, [MoO 2 (O 2 )(L) 2 ] 2− -MR [L = valine (MRVMo) or alanine (MRAMo) and MR = Merrifield resin] were prepared by reacting H 2 MoO 4 with 30% H 2 O 2 and the respective amino acid functionalized resin, at near neutral pH. The compounds were characterized by elemental analysis, spectral studies (FTIR, Raman, 13 C NMR and 95 Mo NMR, diffuse reflectance UV-Vis and XPS), SEM, EDX, XRD, Brunauer-Emmett-Teller (BET) and TGA-DTG analysis. The easy recyclability of the catalysts for several catalytic cycles without change in activity and selectivity, their complete chemoselectivity towards the sulfur group of substrates bearing other oxidation prone functional groups, are important "green" attributes of these catalysts. † Electronic supplementary information (ESI) available: 13 C NMR chemical shifts and thermogravimetric data, N 2 adsorption/desorption isotherms, FTIR spectra, bar diagram for the recyclability of the catalyst, calculation for the efficiency of H 2 O 2 , characterization of sulfoxides and sulfones. See

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Section: Synthesis and Characterizationmentioning

confidence: 99%

Merrifield resin supported peroxomolybdenum(vi) compounds: recoverable heterogeneous catalysts for the efficient, selective and mild oxidation of organic sulfides with H2O2

et al. 2013

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“…In fact, MoO2(acac)2 in solution is not capable to lead to any evident enantiomeric excess for epoxidation, unless chiral ligands are used. 18,19 Moreover, despite frequent depictions of MoO2(acac)2 as trans species with D2h symmetry in modern literature, [20][21][22] trans-MoO2(acac)2 does not exist in the solid state, 23 and its existence in the liquid phase has never been confirmed to the best of our knowledge. As the reactions mentioned above all occur in liquid phase, this prompted us to consider the actual stereochemistry of MoO2(acac)2 in solution.…”

Section: Introductionmentioning

confidence: 99%

Dynamic NMR and Quantum-Chemical Study of the Stereochemistry and Stability of the Chiral MoO₂(acac)₂ Complex in Solution

Conte

Hippler

2016

J. Phys. Chem. A

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The stereochemistry and dynamics of MoO2(acac)2 in benzene, chloroform and toluene was investigated by variable temperature 1 H NMR, density functional theory (SOGGA11-X, B3LYP) and ab initio (MP2) methods. In solution, an equilibrium between two chiral enantiomers with C2 symmetry was identified, Λ-cis-MoO2(acac)2 and ∆-cis-MoO2(acac)2. The two enantiomers are connected via achiral cis transition states that switch the enantiomeric conformations via a RayDutt, Bailar and a newly described racemization twisting mechanism. All three mechanisms have similar calculated activation energies. Activation parameters Ea, ∆H ‡ , and ∆S ‡ were experimentally determined for the exchange process, with a small, negative ∆S ‡ , and a positive ∆H ‡ of 68.1 kJ mol -1 in benzene, 54.9 kJ mol -1 in chloroform, and 60.6 kJ mol -1 in toluene, in reasonable general agreement with the calculations. trans configurations of MoO2(acac)2 are very much higher in energy than cis and are not relevant in the temperature range experimentally studied, 243-340 K. The enantiomers interconvert within seconds near room temperature, and much faster at elevated temperatures. Racemization will thus prevent the use of enantiomerically pure MoO2(acac)2 for chiral catalysis under practical conditions.

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“…Therefore, numerous methods have been introduced for the development of heterogeneous processes, including the use of Schiff base catalysts [8]. For example, transition metal complexes can be supported on polymers [9], immobilised by covalent [10] or coordinative linkages [11], or electrostatic attraction [12] via functionalized ligands or adsorption on porous supports [13] to combine the good activities and selectivities of homogeneous catalysts with the simplicity of recycling and recovery of heterogeneous ones. Another method of heterogenisation is the inclusion of the metal complex in the nanopores of molecular sieves or sol-gel matrices [14,15].…”

Section: Introductionmentioning

confidence: 99%

Synthesis, characterization and catalytic epoxidation of cyclohexene using dimeric cis-dioxomolybdenum(VI) bis-bidentate Schiff base complexes supported on single wall carbon nanotubes

Salavati‐Niasari

Bazarganipour

2008

Transition Met Chem

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Three dimeric cis-dioxomolybdenum(VI) complexes of bis-bidentate Schiff base derivatives containing aromatic nitrogen-nitrogen linkers (4,4 0 -diaminodiphenylmethane; 4,4 0 -diaminodiphenylether; 4,4 0 -diaminodiphenylsulfone) with 2-hydroxy-1-naphthaldehyde have been synthesised and characterized by physico-chemical and spectroscopic methods. The catalytic activities of the complexes with respect to alkene epoxidation using tertbutylhydroperoxide (TBHP) as oxidant have been studied. The addition of single wall nanotubes can enhance the catalytic activities of the Mo complexes and the selectivity of epoxide formation.

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Alkene epoxidations catalysed by Mo(VI) supported on Merrifield's polymer

Cited by 19 publications

References 6 publications

Merrifield resin supported peroxomolybdenum(vi) compounds: recoverable heterogeneous catalysts for the efficient, selective and mild oxidation of organic sulfides with H2O2

Merrifield resin supported peroxomolybdenum(vi) compounds: recoverable heterogeneous catalysts for the efficient, selective and mild oxidation of organic sulfides with H2O2

Dynamic NMR and Quantum-Chemical Study of the Stereochemistry and Stability of the Chiral MoO₂(acac)₂ Complex in Solution

Synthesis, characterization and catalytic epoxidation of cyclohexene using dimeric cis-dioxomolybdenum(VI) bis-bidentate Schiff base complexes supported on single wall carbon nanotubes

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Alkene epoxidations catalysed by Mo(VI) supported on Merrifield's polymer

Cited by 19 publications

References 6 publications

Merrifield resin supported peroxomolybdenum(vi) compounds: recoverable heterogeneous catalysts for the efficient, selective and mild oxidation of organic sulfides with H2O2

Merrifield resin supported peroxomolybdenum(vi) compounds: recoverable heterogeneous catalysts for the efficient, selective and mild oxidation of organic sulfides with H2O2

Dynamic NMR and Quantum-Chemical Study of the Stereochemistry and Stability of the Chiral MoO2(acac)2 Complex in Solution

Synthesis, characterization and catalytic epoxidation of cyclohexene using dimeric cis-dioxomolybdenum(VI) bis-bidentate Schiff base complexes supported on single wall carbon nanotubes

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Dynamic NMR and Quantum-Chemical Study of the Stereochemistry and Stability of the Chiral MoO₂(acac)₂ Complex in Solution