CoFe2O4@SiO2@ Co (III) salen complex nanoparticle as a green and efficient magnetic nanocatalyst for the oxidation of benzyl alcohols by molecular O2

In the presence of cobalt (III) salen complex, selective oxidation of alcohols to carbonyl compounds was studied by molecular oxygen using isobutyraldehyde as an oxygen acceptor. The effect of cobalt (III) salen complex in the oxidation reaction was studied, and the results showed that Co (III) salen complex is very active and selective in the oxidation of various alcohols. Also, the effect of important factors including catalyst amount, solvent and temperature was investigated on the reaction. Furthermore, the catalytic activities of CoFe₂O₄@SiO₂‐supported Schiff base metal complex as well as the effect of molecular oxygen (O₂) as a green oxidant were studied. The results showed that benzaldehyde was the major product and the heterogeneous catalyst was highly reusable.     

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.     

Asymmetric oxidation of sulfides catalyzed by chiral (salen)Mn(III) complexes with a pyrrolidine backbone

Catalytic properties of a series of chiral (pyrrolidine salen)Mn(III) complexes for asymmetric oxidation of aryl methyl sulfides were evaluated. Moderate activity, good chemical selectivity and low enantioselectivity were attained with iodosylbenzene as a terminal oxidant. Enantioselectivity of sulfide oxidation was affected slightly by polar solvent and the sulfoxidation carried out in THF for thioanisole and in CH₃CO₂Et for electron‐deficient sulfides gave better enatioselctivities. The addition of the donor ligand PPNO (4‐phenylpyridine N‐oxide) or MNO (trimethylamine N‐oxide) only has a minor positive effect on the enantioselectivity. Also explored was the steric effect of the N_aza‐substituent in the backbone of (pyrrolidine salen)Mn(III) complexes on the enantioselectivity of sulfide oxidation. The sulfides' access pathway is discussed based on the catalytic results. Copyright © 2006 John Wiley & Sons, Ltd.     

An effective approach for the immobilization of chiral Mn(III) salen complexes through a supported ionic liquid phase

An effective method based on supported ionic liquid system was employed to immobilize chiral Mn(III) salen complexes. The prepared heterogeneous catalysts exhibited excellent activity and enantioselectivity in the asymmetric epoxidation of unfunctionalized olefins. Especially, in the epoxidation of α-methylstyrene, both the conversion and ee value could exceed 99%. Furthermore, the immobilized catalysts were stable and could be recycled three times without loss of activities.     

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.     

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.     

酚氧基修饰的AlPS-PVPA固载手性Salen Mn(III)催化剂的合成及催化烯烃不对称环氧化研究

以有机共聚物-无机杂化材料聚（苯乙烯-苯乙烯基膦酸）-磷酸铝（AlPS-PVPA）为载体,酚氧基为连接基团,轴向配位手性salen Mn（Ⅲ）制备了新型固载手性salen Mn（Ⅲ）催化剂,并运用FT-IR,UV-vis,XPS,SEM,TG,元素分析等手段对其进行了表征.以m-CPBA为氧化剂,茚和α-甲基苯乙烯为底物,考察了催化剂对非功能化烯烃不对称环氧化反应的催化性能.结果表明,在相同的条件下,固载催化剂3a~3d在不加助催化剂NMO时显示出了优良的催化活性,其转化率和ee值均比添加了轴向配体NMO时有很大的提高（ee%,99.2 vs.45.9; conv%,98.6 vs.64.6）,这种现象与大多数文献报道相反.此外,催化剂容易分离,且回收使用9次仍能保持较好的催化活性.     

通过接枝苄基磺酸在MCM-41上固载手性Mn(salen)配合物

首先通过两步后合成处理,在MCM-41上接枝苄基磺酸;然后,以苄基磺酸为过渡产物,用手性Mn(salen)配合物修饰处理,得到了苄基磺酸轴向负载手性Mn(salen)配合物的MCM-41;实现了在廉价且温和条件下均相手性Mn(salen)催化剂的非均相化。采用X射线衍射(XRD)、低温N2吸附-脱附、红外光谱、热重-差示扫描量热(TG-DSC)分析、电感耦合等离子体发射光谱(ICP)和酸度滴定等对样品进行了表征。结果表明,手性Mn(salen)配合物成功固载在MCM-41上,且MCM-41的介孔结构和Mn(salen)配合物的手性特征仍然保留。以间氯过氧苯甲酸为氧化剂,考察了所得固载型催化剂对α-甲基苯乙烯的不对称环氧化催化性能,结果表明在0℃反应2 h,催化剂用量为0.02 mmol,无需加入轴向配体N-甲基吗啉氮氧化物(NMO)的条件下对映体过量(enantiomeric excess,e.e.)值可达99%以上,转化率为77%。归因于苄基磺酸基起到了很好的轴向配体作用。经适当处理,固载型催化剂在循环使用5次后e.e.值依然有71%,表现出较好的活性和重复使用性能。     

通过接枝苄基磺酸在MCM-41上固载手性Mn(salen)配合物

首先通过两步后合成处理,在MCM-41上接枝苄基磺酸;然后,以苄基磺酸为过渡产物,用手性Mn(salen)配合物修饰处理,得到了苄基磺酸轴向负载手性Mn(salen)配合物的MCM-41;实现了在廉价且温和条件下均相手性Mn(salen)催化剂的非均相化。采用X射线衍射(XRD)、低温N₂吸附-脱附、红外光谱、热重-差示扫描量热(TG-DSC)分析、电感耦合等离子体发射光谱(ICP)和酸度滴定等对样品进行了表征。结果表明,手性Mn(salen)配合物成功固载在MCM-41上,且MCM-41的介孔结构和Mn(salen)配合物的手性特征仍然保留。以间氯过氧苯甲酸为氧化剂,考察了所得固载型催化剂对α-甲基苯乙烯的不对称环氧化催化性能,结果表明在0 ℃反应2 h,催化剂用量为0.02 mmol,无需加入轴向配体N-甲基吗啉氮氧化物(NMO)的条件下对映体过量(enantiomeric excess,e.e.)值可达99%以上,转化率为77%。归因于苄基磺酸基起到了很好的轴向配体作用。经适当处理,固载型催化剂在循环使用5次后e.e.值依然有71%,表现出较好的活性和重复使用性能。     

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.     

Mn(III) complex supported on Fe3O4 nanoparticles: magnetically separable nanocatalyst for selective oxidation of thiols to disulfides

A manganese(III) complex, [Mn(phox)₂(CH₃OH)₂]ClO₄ (phox?=?2-(2′-hydroxyphenyl)oxazoline), was immobilized on silica-coated magnetic Fe₃O₄ nanoparticles through the amino propyl linkage using a grafting process in dichloromethane. The resulting Fe₃O₄@SiO₂–NH₂@Mn(III) nanoparticles are used as efficient and recyclable catalysts for selective oxidation of thiols to disulfides using urea-hydrogen peroxide as the oxidant. The nanocatalyst was recycled several times. Leaching and recycling experiments revealed that the nanocatalyst can be recovered, recycled, and reused more than five times, without the loss of catalytic activity and magnetic properties. The recycling of the nanocatalyst in six consecutive runs afforded a total turnover number of more than 10,000. The heterogeneous Fe₃O₄@SiO₂–NH₂@Mn(III) nanoparticle shows more selectivity for the formation of disulfides in comparison with the homogeneous manganese complex.     

大位阻手性吡咯烷(salen)Mn(III)配合物在烯烃不对称环氧化反应中的应用

设计合成了具有大位阻的手性吡咯烷(salen)Mn(III)配合物Mn3,并研究了其在NaClO水/有机两相氧化体系中催化烯烃的不对称环氧化反应性能。 具有叔胺基团的配合物Mn3具有比Jacobsen催化剂更高的反应活性、以及近似的产率和略高的对映选择性。 尤其是过量CH₃I的加入可以极大地缩短环氧化反应的时间,而高产率和高对映选择性依然保持。     

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.     

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.     

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.     

Salen-Mn（Ⅲ）-Complex-Catalyzed Oxidations of Secondary Alcohols

Secondary alcohols were catalytically oxidized with diace-toxyiodobenzene as oxidant in the presence of salen-Mn(Ⅲ)complex to aiTord the eorrespoltding ketones, in up to 99% yield, using CH2Cl2 or water as reaction media.     

MCM-48固载手性salen Mn(III)催化苯乙烯环氧化反应

手性salenMn(III)化合物是非常有效的烯烃不对称环氧化催化剂[1],近年来对它的非均相化研究越来越受到大家的关注[2-4].以聚合物为载体固载salen Mn(III)化合物的研究已经取得了很大的进展,相对的无机载体的研究要少得多.本文首次将手性salen Mn(III)化合物固载到介孔分子筛MCM     

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.     

CoFe2O4@SiO2-NH2-CoII NPs catalyzed Hantzsch reaction as an efficient,reusable catalyst for the facile,green, one-pot synthesis of novel functionalized 1,4-dihydropyridine derivatives

A magnetically heterogeneous CoFe₂O₄@SiO₂-NH₂-Co^II nanoparticle was synthesized by the immobilization of Co (II) complex onto CoFe₂O₄@SiO₂ nanoparticles, and the heterogeneous magnetic nanocatalyst was characterized by XRD, TEM, TGA, EDX, and FT-IR techniques. Then, the green and reusable method was introduced for a multicomponent synthesis of 1,4-dihydropyridine derivatives via Hantszch reaction. The synthesis of 1,4-dihydropyridine derivatives was proceeded by the reaction of aldehyde, ethyl acetoacetate, and ammonium acetate in the presence of this magnetic nanocatalyst in EtOH/Water (1:1). Simple work-up, short reaction times, excellent yields (60–96%) as well as green solvent are some advantages of this novel approach, and the corresponding products were purified with no need for chromatographic separation.     

Mn(III)-catalyzed oxidation of sulfides to sulfoxides with hydrogen peroxide

Sulfides were selectively oxidized to the corresponding sulfoxides in good yields with hydrogen peroxide using a manganese(III) Schiff-base complex as a catalyst in glacial acetic acid as solvent under mild conditions.