Novel organic polymer-inorganic hybrid material zinc poly(styrene-phenylvinylphosphonate)-phosphate prepared with a simple method

A novel type of organic polymer-inorganic hybrid material layered crystalline zinc poly(styrene-phenylvinylphosphonate)-phosphate (ZnPS-PVPP) was synthesized under mild conditions in the absence of any template. And the ZnPS-PVPP were characterized by FT-IR, diffusion reflection UV-vis, AAS, N₂ volumetric adsorption, SEM, TEM and TG. Notably, this method was entirely different from the traditional means used for preparing other zinc phosphonate. Moreover, it could be deduced that ZnPS-PVPP possessed the potential applications for catalyst supports. In the initial catalytic tests, the catalysts immobilized onto ZnPS-PVPP showed comparable or higher activity and enantioselectivity with that of catalysts reported by our group in the asymmetric epoxidation of unfunctional olefins.     

Heterogeneous chiral Mn(III) salen catalysts for the epoxidation of unfunctionalized olefins immobilized on mesoporous materials with different pore sizes

Two chiral Mn(III) salen complexes were immobilized onto a series of mesoporous MCM-41 and MCM-48 materials with different pore sizes and the as-synthesized catalysts were active and enantioselective for the asymmetric epoxidation of styrene and indene. The results of XRD, FTIR, DR UV-vis, and N₂ sorption showed that the chiral Mn(III) salen complexes were anchored in the channels of mesoporous materials. The influence of organic silicane dosage on the catalytic performance was studied and the optimum dosage of organic silicane for preparing heterogeneous catalysts was determined. Furthermore, the effect of the fine-tuning of pore size on the performance of heterogeneous catalysts was discussed. In general, larger pore size of the supports could lead to higher conversions and the compatible pore size with substrate may be responsible for the improved enantiomeric excess (ee) values.     

手性salen(Mn)催化烯烃不对称环氧化反应的研究进展

烯烃的不对称环氧化物通过选择性开环或者官能团的转化,可以生成一系列有价值的手性化合物,被广泛用作医药、农药、香料等精细化学品的合成中间体.手性Mn(salen)金属配合物被证明是烯烃不对称环氧化最有效的催化剂之一.本文综述了近年来均相手性Mn(salen)催化剂、有机聚合物固载的手性Mn(salen)、无机载体固载手性...     

Axially coordinated chiral salen Mn(iii) anchored onto azole onium modified ZnPS-PVPA as effective catalysts for asymmetric epoxidation of unfunctionalized olefins

A series of chiral salen Mn(iii) immobilized onto azole onium modified zinc poly(styrene-phenylvinyl phosphonate)-phosphate (ZnPS-PVPA) were prepared. The catalysts were characterized by FT-IR, diffusion reflection UV-vis, AAS, N(2) volumetric adsorption, SEM, TEM, XPS, XRD, TG and elemental analysis. The results showed that the chiral salen Mn(iii) complex was successfully immobilized onto ZnPS-PVPA. These prepared catalysts were evaluated in the asymmetric epoxidation of unfunctionalized olefins with m-CPBA and NaIO(4) as oxidants and demonstrated higher catalytic activities than those of the corresponding homogeneous chiral salen Mn(iii) catalyst under the same conditions. Moreover, these heterogeneous catalysts were stable and could be recycled nine times without significant loss of activity. Furthermore, this novel type of catalyst could also be validly used in large-scale reactions with superior catalytic disposition being maintained at the same level, which indicated the potential for applications in industry.     

Monodisperse crosslinked pHEMA particle‐supported chiral Mn(III)salen catalyst for asymmetric epoxidation of olefin

Monodisperse crosslinked poly(hydroxyethyl methacrylate) particles (pHEMA) were synthesized for immobilization of the chiral Mn(III)salen homogeneous catalyst by axial coordination. The pHEMA‐Mn(III)salen catalyst was subsequently characterized by FT‐IR, UV and scanning electron microscopy. The results showed that, the heterogeneous Mn(III)salen catalysts also exhibited high activity and enantioselectivity compared to the homogeneous catalyst for the disubstituted cyclic indene and 6‐cyano‐2,2‐dimethylchromene. Moreover, the catalysts were easily separated from the reaction systems and could be renewed several times without significant loss of catalytic activity. Meanwhile, the enantiomeric excess (ee) value remained at 80% in the eighth cycle. The pHEMA support, immobilized by Mn(III)salen, probably acted as a mediator of the reaction between the substrate and the oxidant, and enhanced the stability of the Mn(III)salen compound. Copyright © 2012 John Wiley & Sons, Ltd.     

A novel supported Katsuki-type (salen)Mn complex for asymmetric epoxidation

We have successfully prepared an unsymmetrical analogue of a Katsuki-type salen ligand having a hydroxyalkyl group at the 6-position of just one of the binaphthyl units in the ligand, and also several Mn(III) complexes; these complexes have been attached to a polymer by an ester link and such polymer catalysts have been shown to be highly enantioselective and recoverable catalysts for the epoxidation of 1,2-dihydronaphthalene.     

Asymmetric epoxidation of unfunctionalized olefins catalyzed by chiral salen‐Mn (III) immobilized on alkoxyl‐modified ZnPS‐PVPA

Novel layered heterogeneous chiral salen Mn (III) catalysts anchored onto ZnPS‐PVPA by means of click chemistry are synthesized and employed in asymmetric epoxidations of unfunctionalized olefins. The catalysts manifest superior catalytic performances (conv%, up to >99; ee%, up to >99) according to the epoxidations of α‐methylstyrene, styrene, indene and 1‐octene. But for 6‐cyano‐ 2,2‐dimethylchromene and 6‐nitro‐2,2‐dimethylchromene, configuration of epoxides are reversed. Moreover, the catalysts could still indicate comparable properties (yield, 82%; ee, 86%) after recycling for nine times and excellent functions in large‐scale reactions, which paves the way for the application in industry.     

New chiral (salen)manganese(III) systems for asymmetric epoxidation of styrene

Highly enantioselelctive and repeatable epoxidation of styrene was performed by using new chiral (salen)Mn(III) catalysts, which were derived from the initial immobilization of a homogeneous (salen)Mn(III) complex on solid carriers and subsequent dispersion into ionic liquids. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Enantioselective epoxidation of olefins catalyzed by two novel chiral poly-salen–Mn(III) complexes

Two novel chiral poly-salen–Mn(III) complexes 1 and 2, derived from (R,R)-1,2-diaminocyclohexane and the disalicylaldehydes 5 and 6 were synthesized and employed in the enantioselective epoxidation of olefins. A range of 30–92% ee and 75–97% yield was achieved in NaClO/4-PPNO and m-CPBA/NMO oxidant systems when substituted styrenes and substituted 2,2-dimethylchromenes were used as substrates. Furthermore, the poly-salen–Mn(III) complexes could be recovered easily and recycled efficiently several times by a simple catalysis/separation method. After five reactions, an 82% ee and 78% yield of epoxide were obtained using 2,2-dimethylchromene as substrate.     

A new heterogeneous chiral (salen)manganese(III) system for enantioselective epoxidation of non‐functionalized olefins

This communication describes the design and application of a novel catalytic epoxidation system derived from the initial immobilization of a homogeneous sulfonato (salen)Mn(III) complex on two solid carriers (silica gel and siliceous earth) and subsequent dispersion of the supported manganese complexes into ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMImPF₆) and 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMImBF₄) for recycling. The performance of chiral (salen)Mn(III) system in enantioselective epoxidation of olefins was investigated systematically. Even higher enantioselectivity than that of the homogeneous counterpart was obtained with similar catalytic activity. In particular, the best catalytic result is that the combination of the silica gel‐supported (salen)Mn(III) catalyst and BMImPF₆ affords 97–100% ee for epoxidation of α‐methylstyrene, and high ee values were retained even after three cycles. Copyright © 2010 John Wiley & Sons, Ltd.     

Asymmetric epoxidation of 6-cyano-2,2-dimethylchromene on Mn(salen) catalyst immobilized in mesoporous materials

This article reports our recent work on the heterogeneous asymmetric epoxidation catalyzed by chiral Mn(salen) catalyst axially immobilized via phenoxyl groups and organic sulfonic groups. The asymmetric epoxidation of 6-cyano-2,2-dimethylchromene was especially presented in detail. The factors that affected the asymmetric induction, such as the nanopores and the external surface, the linkage length, and the modification of nanopores with methyl groups were discussed. It was found that the enantioselectivities increased with decreasing the nanopore sizes or increasing the linkage length in nanopore, and the Mn(salen) catalyst immobilized into nanopores generally gave higher ee values than those on the external surface. The heterogeneous Mn(salen) catalysts with modified nanopores gave a TOF of 14.8 h⁻¹ and an ee value of 90.6% for the asymmetric epoxidation of 6-cyano-2,2-dimethylchromene, which were higher than the results (TOF 10.8 h⁻¹, ee 80.1%) obtained for the homogeneous catalyst.     

Influence of the built-in pyridinium salt on asymmetric epoxidation of substituted chromenes catalysed by chiral (pyrrolidine salen)Mn(III) complexes

Chiral (pyrrolidine salen)Mn(III) complexes 1 with an N-benzoyl group and 2 with an N-isonicotinoyl group as well as the corresponding N-methyl (3) and N-benzyl (4) pyridinium salts of 2 were synthesized. The catalytic properties of 1–4 and 2 with excess CH₃I were explored to figure out the influence of the internal pyridinium salt in the catalyst on asymmetric epoxidation of substituted chromenes with NaClO/PPNO as an oxidant system in the aqueous/organic biphasic medium. The (pyrrolidine salen)Mn(III) complexes with an internal pyridinium salt, either formed in situ or isolated, displayed higher activities than analogous complexes 1, 2 and Jacobsen's catalyst in the aforementioned reaction, with comparable high yields and ee values. The acceleration of the reaction rate is attributed to the phase transfer capability of the built-in pyridinium salt of the (salen)Mn(III) catalyst. The effect of the internal pyridinium salt on the epoxidation of substituted chromenes is similar to that of the external pyridinium salts and ammonium halides.     

Chiral Mn(III) salen complex immobilized on imidazole-modified mesoporous material via co-condensation method as an effective catalyst for olefin epoxidation

An imidazole modified mesoporous material has been prepared through a co-condensation procedure and adopted to covalently anchor chiral Mn(III) salen complex. The active centers in the as-synthesized catalyst were presented in the form of ionic species. The results of XRD, FTIR, DRUV-Vis, and N₂ sorption confirmed the successful immobilization of chiral Mn(III) salen complex inside the channels of the modified support and the maintenance of the mesoporous structure of parent support in the immobilized catalyst. This heterogeneous catalyst exhibited comparable catalytic activity and enantioselectivity to those of the homogeneous counterpart in the asymmetric epoxidation of unfunctionalized olefins. Furthermore, notably high turnover frequencies have been obtained over this heterogeneous catalyst for the relatively short reaction time and low catalyst amount, due in part to the ionic property as well as the uniform distribution of the active centers.     

非血红素N4配体Mn(III)配合物催化烯烃的不对称环氧化反应

利用Mn(OAc)3与手性四氮配体制备了非血红素N4配体的Mn(Ⅲ)配合物,并将其应用于催化α,β-不饱和烯酮和简单烯烃的不对称环氧化反应,考察了氧化剂H2O2的量和添加剂HOAc的量等条件对反应结果的影响,研究了该催化剂的底物适用范围,获得了51%~94%的ee值.     

Enantioselective epoxidation of unfunctionalised olefins catalyzed by Mn(salen) complexes immobilized in porous materials via phenyl sulfonic group

Heterogeneous chiral Mn(salen) catalysts axially immobilized on mesoporous materials via phenyl sulfonic groups result in remarkably higher ee values (up to 95%) for asymmetric epoxidation of unfunctionalised olefins.     

Dual-mode EPR study of Mn(III) salen and the Mn(III) salen-catalyzed epoxidation of cis-beta-methylstyrene

Dual-mode electron paramagnetic resonance (EPR), in which an oscillating magnetic field is alternately applied parallel or perpendicular to the static magnetic field, is a valuable technique for studying both half-integer and integer electron spin systems and is particularly useful for studying transition metals involved in redox chemistry. We have applied this technique to the characterization of the Mn(III) salen (salen = N,N'-ethylene bis(salicylideneaminato)) complex [(R,R)-(-)-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminomanganese(III)], with an S = 2 integer electron spin system. Furthermore, we have used dual-mode EPR to study the Mn salen complex during the Mn(III) salen-catalyzed epoxidation of cis-beta-methylstyrene. Our study shows that the additives N-methylmorpholine N-oxide (NMO) and 4-phenylpyridine-N-oxide (4-PPNO), which are used to improve epoxidation yields and enantioselection, bind to the Mn(III) center prior to the epoxidation reaction, as evidenced by the alteration of the Mn(III) parallel mode EPR signal. With these additives as ligands, the axial zero-field splitting values and (55)Mn hyperfine splitting of the parallel mode signal are indicative of an axially elongated octahedral geometry about the Mn(III) center. Since the dual-mode EPR technique allows the observation of both integer and half-integer electron spin systems, Mn oxidation states of II, III, IV, and potentially V can be observed in the same sample as well as any radical intermediates or Mn(III,IV) dinuclear clusters formed during the Mn(III) salen-catalyzed epoxidation reaction. Indeed, our study revealed the formation of a Mn(III,IV) dinuclear cluster in direct correlation with expoxide formation. In addition to showing the possible reaction intermediates, dual-mode EPR offers insight into the mechanism of catalyst degradation and formation of unwanted byproducts. The dual-mode technique may therefore prove valuable for elucidating the mechanism of Mn(III) salen catalyzed reactions and ultimately for designing optimum catalytic conditions (solvents, oxidants, and additives such as NMO or 4-PPNO).     

Synthesis and characterization of a new kind of immobilized Mn(salen) and catalytic epoxidation of styrene on the catalyst

A linear polystyrene‐isopropenyl phosphonic acid (PS‐IPPA) copolymer was newly synthesized by free radical reaction in solution with isopropenyl phosphonic acid (IPPA) and styrene. Zirconium poly(styrene‐isopropenyl phosphonate)‐phosphate acid (ZPS‐IPPA) was also synthesized. The benzene rings of ZPS‐IPPA were hydroxylated and then further reacted with Mn(salen)Cl. Thus the heterogeneous catalyst, Mn(salen) axially immobilized onto ZPS‐IPPA was synthesized. These substances were characterized by IR spectra, X‐ray diffraction (XRD), SEM, TEM, NMR, thermogravimetric analysis, and AAS. The catalyst showed good activity to epoxidation of styrene, which is close to that of the corresponding homogeneous catalyst. Copyright © 2008 John Wiley & Sons, Ltd.     

DNA-binding and cleavage studies of chiral Mn(III) salen complexes

Chiral bridge-substituted manganese(III) complexes of N,N′-bis-(2-hydroxynaphthalene-1-carbaldehyde)-(1R,2R)-(−)-diaminocyclohexane and N,N′-bis-(2-hydroxynaphthalene-1-carbaldehyde)-(1S,2S)-(+)-diaminocyclohexane have been synthesized. The interaction of these complexes with calf thymus DNA(CT-DNA) was investigated by spectroscopic, thermal denaturation studies, circular dichroism (CD), and viscosity measurements. Results of spectroscopic and viscosity measurements suggest that the two complexes bind to DNA via an intercalative mode and display enantioselectivity. These Mn(III) complexes have been found to promote the cleavage of plasmid DNA pBR322 in the presence of H₂O₂.     

A chiral Mn(III) salen complex immobilized onto ionic liquid modified mesoporous silica for oxidative kinetic resolution of secondary alcohols

A supported ionic liquid strategy has been applied for the immobilization of a chiral Mn(III) salen complex onto ionic liquid modified mesoporous silica SBA-15. The immobilized catalyst demonstrated high enantioselectivity and activity in the oxidative kinetic resolution of secondary alcohols, and could be recycled five times without obvious loss of activity.     

Asymmetric Mn(III)-salen catalyzed epoxidation of unfunctionalized alkenes with in situ generated peroxycarboxylic acids

Unfunctionalized aromatic alkenes were enantioselectively epoxidized with peroxycarboxylic acids prepared in situ from urea-H₂O₂ (and other anhydrous adducts of H₂O₂) and carboxylic acid anhydrides (maleic, phthalic, and acetic anhydride) using chiral Mn(III)-salen complexes as catalysts and N-methylmorpholine N-oxide (NMO) as an additive. Experimental results were compared with those reported earlier that employed aqueous hydrogen peroxide as the primary oxidant and the method presented here was found to offer both higher enantioselectivities and shorter reaction times. This novel epoxidation system was also compared with the Jacobsen’s MCPBA/NMO system, and some differences in reactivity and selectivity were observed. These differences could possibly be explained assuming the presence of alternative mechanistic pathways during the catalytic cycle of the asymmetric epoxidation.