Polymer-supported salen complexes for heterogeneous asymmetric synthesis: Stability and selectivity

Angelino, Mark D.; Laibinis, Paul E.

doi:10.1002/(sici)1099-0518(19991101)37:21<3888::aid-pola2>3.0.co;2-b

Cited by 63 publications

(35 citation statements)

References 56 publications

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“…This mostly led to a decrease in selectivity unless there was no covalent interaction between the complex and the host, allowing a high freedom of movement [30]. One possible approach to immobilizing the complex is building it up piece by piece on the solid support, as reported by Angelino et al [28,29] In this paper a similar approach is used anchoring the catalyst on a chloromethylated MIL-101.…”

Section: Catalystsupporting

confidence: 75%

“…Both symmetrical and asymmetrical salen complexes will be investigated to get an in-depth view on the effect of substituents at various positions of the ligands on the selectivity. This is important when considering the effect of the covalent grafting of salen-type complexes, where an asymmetric substitution is often used to bind the complex to a support [27][28][29]. Such grafting procedures, or in general the immobilization of the homogeneous system into a heterogeneous system might be beneficial.…”

Section: Catalystmentioning

confidence: 96%

“…This material has been chosen for the high stability in the various media that are used in the postmodification process. There have been various studies where the salen complex was immobilized on different supports [28,29,[33][34][35]. This mostly led to a decrease in selectivity unless there was no covalent interaction between the complex and the host, allowing a high freedom of movement [30].…”

Section: Catalystmentioning

confidence: 99%

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The enantioselectivity of the manganese-salen complex in the epoxidation of unfunctionalized olefins and the influence of grafting

Bogaerts

Wouters

Voort

et al. 2015

Journal of Molecular Catalysis A: Chemical

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Section: Catalystsupporting

confidence: 75%

Section: Catalystmentioning

confidence: 96%

Section: Catalystmentioning

confidence: 99%

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The enantioselectivity of the manganese-salen complex in the epoxidation of unfunctionalized olefins and the influence of grafting

Bogaerts

Wouters

Voort

et al. 2015

Journal of Molecular Catalysis A: Chemical

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“…Initially organic polymers were extensively used to covalently anchor Mn(III) salen catalysts, but limited success was reported mainly due to the lack of stability of the supports under the epoxidazing conditions [7][8][9][10][11][12]. Due to their higher stability in reaction media, inorganic Electronic supplementary material The online version of this article (doi:10.1007/s10562-008-9793-x) contains supplementary material, which is available to authorized users.…”

Section: Introductionmentioning

confidence: 99%

Enantioselective Epoxidation of Alkenes by Jacobsen Catalyst Anchored onto Aminopropyl-functionalised Laponite, MCM-41 and FSM-16

et al. 2008

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The Jacobsen catalyst derivative, (R,R)-[Mn(3,5-dtButsalhd)]ClO 4 -CAT 2, was immobilized through axial coordination of the metal center onto a Laponite, MCM-41 and FSM-16 functionalized with 3-aminopropyltriethoxysilane. The catalytic activity of the Mn-based materials was screened for the enantioselective epoxidation of three olefins: styrene, a-methylstyrene and 6-CN-2,2 0 -dimethychromene, using m-CPBA/NMO as oxidant, and the results were compared with the corresponding homogenous complex (CAT 2) and with the Jacobsen's catalyst, (R,R)-[Mn(3,5-dtButsalhd)Cl]-CAT 1.The results indicate that under comparable condition, the Laponite-based materials show both, higher epoxide yield and enantiomeric excess (ee%) compared to MCM-41 and FSM-16-based materials. The best ee% value was obtained for the substrate 6-CN-2,2 0 -dimethylchromene (64%) which is very close to that obtained with CAT 2 (67%) in homogeneous phase; for the two regular mesoporous materials (MCM-41 and FSM-16) the catalytic results were more favorable for the FSM-16 samples.

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“…[12][13][14] In fact, the above problem is generally encountered for the immobilization of the molecular catalysts with a bimolecular reaction pathway.…”

mentioning

confidence: 99%

Promoted activity of Cr(Salen) in a nanoreactor for kinetic resolution of terminal epoxides

Bai

Peng

et al. 2012

Chem. Sci.

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Cr(Salen) catalyzed kinetic resolution of terminal epoxides via asymmetric ring opening (ARO) with TMSN 3 is an important approach for the synthesis of enantiopure 1,2-amino alcohols, however, the high catalyst usage amount (1-2 mol%) impedes its practical applications. An efficient solid nanoreactor was constructed by encapsulation of Cr(Salen) and pyridine in the nanocages of mesoporous silica. This solid nanoreactor exhibits high activity (TOF: 1325 h À1) and high enantioselectivity (91% ee) for the kinetic resolution of 1,2-epoxyhexane via ARO with TMSN 3 at a catalyst concentration as low as 0.002 mol%, whereas the homogeneous counterpart affords almost no conversion of epoxide under similar reaction conditions. The high activity of the solid nanoreactor is mainly attributed to the greatly intensified cooperative activation in the nanocages as evidenced by the sharply increased TOF in parallel with Cr(Salen) concentration in each nanocage. The increased nucleophilicity of Cr(Salen) after coordination to pyridine could also promote the catalytic activity. The solid nanoreactor can be easily separated and recycled. We demonstrated the possibility for designing an efficient solid nanoreactor for asymmetric catalysis by taking the advantages of the cooperative activation.The synthesis of enantiopure 1,2-amino alcohols through the kinetic resolution of terminal epoxides via asymmetric ring opening (ARO) with TMSN 3 on Cr(Salen) was first reported by Jacobsen and co-workers.1,2 However, high catalyst concentration (1-2 mol%) is needed to achieve desirable activity and enantioselectivity due to the bimolecular reaction pathway and the low activity of Cr(Salen).3 For enhancing the activity, dimeric Cr(Salen) catalysts were prepared and they can catalyze the ARO of epoxide at concentrations an order of magnitude below the lower limit of reactivity of their monomer counterparts due to the enhanced cooperative activation effect. 4Recycling the homogeneous catalysts is quite important regarding the green, atomic efficient, economic and sustainable production of chemicals for the practical applications. Thus far, several heterogenization strategies have been described for Cr(Salen) catalysts for ARO reactions.5-7 However, the reduced activity and enantioselectivity of Cr(Salen) covalently bonded to solid supports through ligand tethering was observed because of the impossible concerted participation of two Cr(Salen) complexes required for the bimetallic activation pathway. 8Cr(Salen) complexes were also immobilized on solid support through a weak interaction, such as coordinative bond or electrostatic adherence.9 During the reaction, equilibrium is reached and part of the Cr(Salen) complexes migrates to the solution for promoting the reaction in the homogeneous phase. The weak interaction between the metal salen complex and supports is the driving force to rebind the complex to the solid through a mechanism that has been termed as boomerang catalyst. Although the asymmetric induction in this case can be as high as the h...

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Polymer-supported salen complexes for heterogeneous asymmetric synthesis: Stability and selectivity

Cited by 63 publications

References 56 publications

The enantioselectivity of the manganese-salen complex in the epoxidation of unfunctionalized olefins and the influence of grafting

The enantioselectivity of the manganese-salen complex in the epoxidation of unfunctionalized olefins and the influence of grafting

Enantioselective Epoxidation of Alkenes by Jacobsen Catalyst Anchored onto Aminopropyl-functionalised Laponite, MCM-41 and FSM-16

Promoted activity of Cr(Salen) in a nanoreactor for kinetic resolution of terminal epoxides

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