Noncovalent Immobilization of Enantioselective Catalysts

Fraile, José M.; Garcı́a, José I.; Mayoral, José A.

doi:10.1021/cr800363y

Cited by 321 publications

(186 citation statements)

References 246 publications

(395 reference statements)

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“…[16] However, immobilization through grafting and anchoring of the molecular catalysts on a solid surface (e.g. Al 2 O 3 or SiO 2 with a high specific surface area) is often detrimental to their catalytic performance, as the strong interaction with the surface alters the structure and chemical properties of the molecular catalyst.…”

Section: Methodsmentioning

confidence: 99%

Hydration of Epoxides on [Co^III(salen)] Encapsulated in Silica‐Based Nanoreactors

Bai

Wang

et al. 2012

Angewandte Chemie

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Monoethylene glycol (MEG) and 1,2-propylene glycol (PG) are important raw materials for the manufacture of polyester resins, antifreezes, cosmetics, medicines, and other products. [1] The total global demand for MEG has been estimated to be over 19 million metric tons per year.[2] The production of MEG in industry predominantly involves the liquid-phase hydration of ethylene oxide (EO), whereby a large excess of water (20-25 mol of water/mol of EO) is required for the high conversion of EO and high selectivity for MEG. The concentration of MEG in the final aqueous solution is only approximately 10 wt %, and huge energy is consumed for the distillation of the product from the aqueous solution. As a result, epoxide hydration is one of the most cost-and energy-intensive processes in the chemical industry.Possible catalytic hydration processes have been extensively investigated for the environmentally friendly production of MEG at a low energy cost. Various types of catalysts, including liquid and solid acids or bases, have been explored, such as sulfuric acid, [3] the salts of some acids, [4] cyclic amines, [5] cation-and anion-exchange resins, [6] quaternary phosphonium halides, [7] polymeric organosilane ammonium salts, [8] macrocyclic chelating compounds, [9] and supported metal oxides.[10] However, a high H 2 O/EO molar ratio (i.e. > 10) is still required for high MEG selectivity. The MEG selectivity is very low at low H 2 O/EO molar ratios owing to the formation of diethylene glycol (DEG) and triethylene glycol (TEG) by the self-condensation of MEG, which is readily catalyzed by acid and base catalysts. Moreover, the inherent corrosion and environmental problems associated with the liquid acids/bases limit their application in industry. The development of an efficient and environmentally benign process for the hydration of epoxides with an H 2 O/epoxide molar ratio approaching the stoichiometric value of the chemical reaction is still a huge challenge.In this study, we developed a solid catalyst that is different from the conventional liquid/solid acid or base catalysts for the hydration of epoxides. We constructed the solid catalyst by encapsulating the molecular catalyst [Co III (salen)], with a salen ligand derived from 3,5-di-tert-butylsalicyclaldehyde and trans-1,2-diaminocyclohexane, [11] in the nanocage of the mesoporous silica FDU-12. This catalyst exhibits high activity and selectivity in the hydration of epoxides under mild reaction conditions. Furthermore, the H 2 O/epoxide molar ratio can be decreased to as low as 2:1 while maintaining the conversion of EO above 98 % and the selectivity for MEG above 98 %. This novel catalytic approach has great potential for the green and energy-saving hydration of epoxides, as well as many other conventional chemical reaction processes in industry.The solid catalyst (denoted as FDU-12-[Co III

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Section: Methodsmentioning

confidence: 99%

Hydration of Epoxides on [Co^III(salen)] Encapsulated in Silica‐Based Nanoreactors

Bai

Wang

et al. 2012

Angewandte Chemie

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“…Please do not adjust margins Please do not adjust margins Coordination polymers were formed by mixing the corresponding polytopic ligand (3)(4)(5)(6) and Cu(OAc) 2 in the appropriate Cu/L molar ratio (Fig. 2).…”

Section: Synthesis Of Polytopic Ligands and Preparation Of Coordinatimentioning

confidence: 99%

Polytopic bis(oxazoline)-based ligands for recoverable catalytic systems applied to the enantioselective Henry reaction

et al. 2015

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Several kinds of polytopic chiral ligands (including ditopic, tritopic and tetratopic), based on the bis(oxazoline) and azabis(oxazoline) motifs, have been tested in the preparation of recoverable catalytic systems for the Henry reaction. The results obtained with the different ligands are, in general, good, but they point to the existence of a delicate balance between the coordinating ability of the ligand, the catalytic activity and the recovery of the catalyst by formation of the coordination polymer, related to the easiness to form oligomeric species in solution.

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“…Based on these facts, early work of biphasic scCO 2 IL hydroformylation was done by Leitner [52,53] and Erkey [54,55] with windowed batch reactors. Later on, Cole-Hamilton built the first scCO 2 continuousflow hydroformylation reactor system [56] utilizing ionic rhodium complex derived from Rh 2 (OAc) 4 and [PhP( 6 ]. Hydroformylation of 1-octene was carried out using scCO 2 as a transport vector for both gaseous and liquid substrates and products ( Figure 15).…”

Section: Supercritical Fluid-ionic Liquid Biphasic Systemmentioning

confidence: 99%

“…In addition, rhodium-catalyzed hydroformylation has not yet been commercialized for C6 or longer linear alkenes because separation of the low volatility aldehydes from the thermally unstable Rh catalyst remained a problem [3]. To enhance the efficiency of catalyst recovery, while still keeping the advantage of using a homogeneous catalytic system, researchers made efforts in largely two categories of catalyst modification: (1) heterogenization, which means anchoring the catalyst on a soluble or insoluble support [4,5]; (2) using a biphasic system [6]. Problems with the latter approach include insufficient catalyst usage and variability in phase separation.…”

Section: Introductionmentioning

confidence: 99%

Recent Advances in Continuous Rhodium-Catalyzed Hydroformylation

Wang¹

2015

J Flow Chem

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Noncovalent Immobilization of Enantioselective Catalysts

Cited by 321 publications

References 246 publications

Hydration of Epoxides on [Co^III(salen)] Encapsulated in Silica‐Based Nanoreactors

Hydration of Epoxides on [Co^III(salen)] Encapsulated in Silica‐Based Nanoreactors

Polytopic bis(oxazoline)-based ligands for recoverable catalytic systems applied to the enantioselective Henry reaction

Recent Advances in Continuous Rhodium-Catalyzed Hydroformylation

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Noncovalent Immobilization of Enantioselective Catalysts

Cited by 321 publications

References 246 publications

Hydration of Epoxides on [CoIII(salen)] Encapsulated in Silica‐Based Nanoreactors

Hydration of Epoxides on [CoIII(salen)] Encapsulated in Silica‐Based Nanoreactors

Polytopic bis(oxazoline)-based ligands for recoverable catalytic systems applied to the enantioselective Henry reaction

Recent Advances in Continuous Rhodium-Catalyzed Hydroformylation

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Product

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Hydration of Epoxides on [Co^III(salen)] Encapsulated in Silica‐Based Nanoreactors

Hydration of Epoxides on [Co^III(salen)] Encapsulated in Silica‐Based Nanoreactors