Alkene epoxidation catalysed by binuclear manganese complexes

Binuclear manganese(II) complexes with macrocyclic ligands have been synthesized by template Schiff base condensation of diethylenetriamine and pentane-2,4-dione or 1,3-diphenyl-propane-1,3-dione. Catalytic epoxidation of simple olefins with hydrogen peroxide and t-BHP were studied using the above manganese complexes in the presence of a base. The influence of reaction temperature, the additive methanol and the cocatalyst had been investigated. The major products of the oxidations were the epoxides. The new manganese complexes showed significant catalytic activities for the epoxidation of alkenes using hydrogen peroxide as oxidant and ammonium acetate as cocatalyst.     

非血红素铁、锰配合物催化烯烃不对称环氧化反应研究进展

手性环氧化物是重要的有机反应中间体.金属氧化酶催化的氧化反应通常具有高效、高选择性、反应条件温和和绿色的特点,模拟其中的非血红素铁加氧酶设计合成一系列手性四氮铁锰配合物催化烯烃不对称环氧化反应成为获得高产率、高对映选择性的手性环氧化物的一个重要方法.本文综述了近年来非血红素手性四氮铁锰配合物催化烯烃不对称环氧化反应的研究进展及相应的机理研究.     

脯氨酸衍生的胺基吡啶四氮锰配合物催化双氧水参与的烯烃不对称环氧化反应（英文）

自然界中存在许多的金属酶,它们参与促进各种各样的氧化反应,例如羟化反应,环氧化反应等.金属酶催化的反应具有催化效率高、反应条件温和、选择性高等优点.受大自然中的金属酶结构及其性质的启发,人们提出了仿生催化氧化的理念,并开始对金属酶进行模拟,致力于发展清洁氧化的反应方式.在过去的几十年中,科学家们设计合成了一系列仿生金属配合物催化剂.例如,利用非手性的乙二胺骨架设计合成出四齿氮配体MEP(N,N'-dimethylN,N'-bis(2-pyridinylmethyl)ethane-1,2-diamine),将其制备成相应的铁配合物催化剂,该铁催化剂可以很好的实现脂肪族烯烃的环氧化,产率高达90%.2003年,Stack小组首次报道了利用手性N,N-二甲基环己二胺骨架衍生的四齿氮配体金属配合物Mn-MCP-(OTf)2(MCP=N,N-dimethyl-N,N-bis(2-pyridylmethyl)cyclohexane-trans-1,2-diamine)催化的不对称环氧化反应.该反应的对映选择性仅仅为10%.因此,发展新型手性四氮配体金属配合物,用于高产率、高对映选择性的不对称环氧化反应,值得进行深入研究.近年来发展的一些含手性二胺骨架的四齿氮配体,例如PDP(2-[[2-(1-(pyridin-2-ylmethyl)-pyrrolidin-2-yl)pyrrolidin-1-yl]methyl]pyridine),被应用到不对称环氧化反应中,但是其手性二胺骨架为联吡咯,价格昂贵,难以制备.这在很大程度上限制了其在不对称合成中的实际应用.因此,利用一些易于合成的手性二胺骨架,发展结构新颖、催化性能优良的四氮金属配合物,成为实现高效、高选择性不对称环氧化反应的关键.在之前的工作基础上,本文以简单易得、价格低廉的天然氨基酸——L-脯氨酸为起始原料,选取吡啶环和含取代基的吡啶环作为侧基氮供体,制备了三种手性四齿氮配体.随后,我们利用新发展的手性四齿氮配体,合成了相应的锰配合物,并且分别将其运用于烯烃不对称环氧化反应中,仔细评估了这些锰金属配合物的催化性能.建立了以0.2 mol%的锰配合物为催化剂,0.5当量的2,2-二甲基丁酸为添加剂,30%双氧水为氧化剂,反应温度为–30 oC,乙腈为溶剂的催化不对称环氧化反应体系.反应结果显示:该催化剂催化的不对称环氧化反应底物适用性广泛,其中苯乙烯、苯并吡喃、烯酰胺等化合物均可以被成功地转化为相应的环氧化物,得到中等至优异的对映选择性(产率最高可达95%,对映选择性最高可达99%).     

负载锰卟啉催化乙酰胆固醇的选择性环氧化

多相金属卟啉催化剂已经被用于普通烯烃的环氧化,如表面修饰的多孔分子筛(MCM 41)[1 3],本文制备了高分子负载型锰卟啉用作胆固醇的非对映选择性环氧化催化剂。转化率可达100%,β选择性可达99%。1　实验部分乙酰胆固醇按文献[4]合成。溶剂均为AR级,按文献方法纯化。将Merrifield sPeptideresin(Aldrich,2%,交联度,200-400目,≈2mmolCl/g)加入到精制的DMF中,室温下放置24h,加入5-(对羟基苯基)-10,15,20-三(对甲基苯基)卟啉及无水K2CO3,N2保护下,80℃反应6h,洗涤干燥得到催化剂[1](图1)。催化环氧化反应　将PhIO及催化剂按化学计…     

Ruthenium carbonyl complexes in catalytic epoxidation of olefins co‐catalyzed by isobutyl‐aldehyde

The present work shows the catalytic activity of a series of carbonyl ruthenium complexes in the epoxidation of olefins co‐catalyzed by isobutyl‐aldehyde. The complexes display catalytic activity in the epoxidation of the cyclohexene with high selectivity. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis of catalytically active polymer-bound Schiff base manganese complexes for selective epoxidation of unfunctionalized olefins

A polymerizable unsymmetric tetradentate Schiff base with one vinyl group 3 was synthesized and copolymerized with styrene in toluene. Mn(III) ion was quantitatively incorporated into the copolymers by the functional moieties. The resulting linear polymer-bound manganese complexes ( 4a ′ and 4b ′) were used as catalyst under homogeneous condition for selective epoxidation of unfunctionalized olefins (i.e. styrene, α-methylstyrene and cyclohexene) at room temperature in the presence of iodosylbenzene (PhIO) as the terminal oxidant. The efficacy of epoxidation using the polymeric catalysts was comparable to that of the monomolecular analog. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3249–3254, 1997     

An environmentally benign route for epichlorohydrin from allyl chloride epoxidation catalyzed by heteropolyphosphatotungstate

In the absence of organic solvent, allyl chloride was epoxidized with aqueous hydrogen peroxide catalyzed by a heteropolyphosphatotungstate catalyst with very good activity and recycling activity. Under optimized conditions, an epichlorohydrin yield of 88.7% was achieved in the first run; after two recycles, the epichlorohydrin yield remained still above 85.0%. Various factors affecting the catalytic reaction were investigated systematically. The reaction rate of hydrogen peroxide in the epoxidation of allyl chloride is zero order with respect to hydrogen peroxide. The activation energy is 52.27 kJ/mol.     

Highly selective olefin epoxidation with manganese triazacyclononane complexes: Impact of ligand substitution

Manganese complexes of 1,4,7-triazacyclononane with different substituents catalyze the selective epoxidation of a large number of olefins to epoxides with H₂O₂. The activities of complexes with methyl (L₁), 2-hydroxybutyl (L₂) and acetato (L₃) substituents are compared. The effects of solvent and temperature on the epoxide yield are very different for the three complexes. It is proposed that these differences are related to the binding of the pendant arms in Mn---L₂ and Mn---L₃ complexes. In general, acetone or methanol are preferred solvents. Variations of stereoretention are also observed: with Mn---L₁ in acetone, isomer scrambling occurs, while with Mn---L₁ in methanol, the epoxidation is almost stereospecific. UV-visible and electron spin resonance spectroscopy are used to characterize the state of manganese under oxidizing conditions.     

Biphasic epoxidation of 1-octene with H2O2 catalyzed by amphiphilic fluorinated Ti-loaded zirconia

A series of amphiphilic fluorinated zirconia containing titanium was prepared by titanium impregnation followed by fluorination and alkylsilylation of zirconium oxide. Physical properties of the resulting samples were characterized by XRD analysis, UV-vis spectroscopy, BET surface area analysis and EDAX analysis. The effects of fluorine and alkylsilane groups on the samples were studied by the epoxidation of 1-octene with aqueous hydrogen peroxide. The epoxidation of alkenes is one of the most important methods of functionalizing simple hydrocarbons. The amphiphilic fluorinated catalysts were more active and more efficient than the conventional titania-silica and zirconia-silica mixed oxides in linear alkene epoxidation; enhanced by the presence of alkylsilane and fluorine groups in the catalysts. Modification with alkylsilane successfully induces the hydrophobic behavior of zirconia which is hydrophilic in nature; whereas fluorine was chosen for its electron-withdrawing effect which further activates the titanium active sites.     

Asymmetric epoxidation of chromenes catalyzed by chiral pyrrolidine SalenMn(III) complexes with an anchored functional group

Chiral pyrrolidine SalenMn(III) complexes with an anchored functional group at the N_aza‐substituent in the pyrrolidine backbone were synthesized, and used as catalysts for asymmetric epoxidation of substituted chromenes. The complex 1 with an anchored imidazole as acceptor could effectively catalyze epoxidation of substituted chromenes in the absence of expensive additive 4‐phenyl pyridine N‐oxide (PPNO) by the coordination of the anchored organic base to the central manganese ion. Complexes 2 and 3 with a quaternary ammonium salt unit at the N_aza‐substituent in the pyrrolidine backbone displayed higher activities than Jacobsen catalyst and the analogous complex 4 without anchored functional group in the aforementioned reaction. Copyright © 2008 John Wiley & Sons, Ltd.     

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.     

Nitration of Halterman porphyrin: a new route for fine tuning chiral iron and manganese porphyrins with application in epoxidation and hydroxylation reactions using hydrogen peroxide as oxidant

A methodology is reported for the regioselective nitration of the phenyl groups of Halterman porphyrin, using NaNO₂. These nitro-porphyrins can be reduced to aminoporphyrins and then N-dimethylated to give new optically active porphyrins. Applications to the asymmetric epoxidation of styrene derivatives by H₂O₂ to give optically active epoxides (ee up to 60%) and hydroxylation of alkanes to give optically active secondary alcohols (ee up to 69%) were carried out in organic solvents (dichloromethane/methanol) using chiral iron and manganese porphyrins as catalysts.     

Dinuclear metal complexes of Schiff base ligands as catalysts for oxidation and epoxidation reactions

Dinuclear copper(II) complexes (Cu₂ L_nCl₃), nickel(II) complexes (Ni₂ L_nCl₃) and cobalt(II) complexes (Co₂L ₂ ⁿ Cl₂) from Schiff base ligands are synthesised, characterised and used as catalysts for oxidation of 3,5-DTBC to 3,5-DTBQ. (Cu₂L_nCl₃) are found to be more efficient than the other complexes. Dinuclear iron(III) complexes of composition (Fe₂L₂Cl₂) and ruthenium (III) complexes of composition Ru₂L ₂ ⁿ Cl₆(PPh₃)₂ and Ru₂L ₂ ⁿ Cl₂(PPh₃)₂ catalyse epoxidation of styrene and cyclohexene. Catalytic activities of ruthenium(III) complexes are much greater than those of analogous iron(III) complexes.     

A simple and effective catalytic system for epoxidation of aliphatic terminal alkenes with manganese(II) as the catalyst

A simple catalytic system that uses commercially available manganese(II) perchlorate as the catalyst and peracetic acid as the oxidant is found to be very effective in the epoxidation of aliphatic terminal alkenes with high product selectivity at ambient temperature. Many terminal alkenes are epoxidised efficiently on a gram scale in less than an hour to give excellent yields of isolated product (>90 %) of epoxides in high purity. Kinetic studies with some C9-alkenes show that the catalytic system is more efficient in epoxidising terminal alkenes than internal alkenes, which is contrary to most commonly known epoxidation systems. The reaction rate for epoxidation decreases in the order: 1-nonene>cis-3-nonene>trans-3-nonene. ESI-MS and EPR spectroscopic studies suggest that the active form of the catalyst is a high-valent oligonuclear manganese species, which probably functions as the oxygen atom-transfer agent in the epoxidation reaction.     

Asymmetric epoxidation of styrenes catalyzed by molybdenum complexes with amino alcohol ligands

Two common amino alcohols, prolinol and isolucinol, and their derivatives have been screened to coordinate with MoO₂(acac)₂ to form in situ catalysts for asymmetric epoxidation of styrenes with the highest enantioselectivity of 84% for 4-fluoro-styrene under the optimized reaction conditions.     

Asymmetric epoxidation of cis-1-propenylphosphonic acid (CPPA) catalyzed by chiral tungsten(VI) and molybdenum(VI) complexes

In the presence of 5.0 mol% chiral tungsten(VI) and molybdenum(VI) complexes, the catalytic asymmetric epoxidation of cis-1-propenylphosphonic acid (CPPA) with 30% aqueous H₂O₂ affording (1R,2S)-(−)-(1, 2)-epoxypropyl phosphonic acid (fosfomycin) was first described. The enantioselectivities of the tungsten and molybdenum catalysts depend strongly on the ligands, reaction temperature and solvent. In CH₂Cl₂ at 0 °C for 72 h, complex MoO₂[(+)-campy]₂ catalyzed the asymmetric epoxidation in a 100% conversion of CPPA with the highest 80% ee. The mechanism of the present epoxidation could be described as direct oxygen transfer occurred on the interface of the biphasic H₂O-nonprotic system.     

Epoxidation of olefins catalyzed by manganese(III) porphyrin in a room temperature ionic liquid

The epoxidation of several alkenes catalyzed by (meso-tetrakis(pentafluorophenyl)porphinato) manganese(III) chloride (MnTFPPCl) was carried out in a 3:1 [bmim]PF₆ ionic liquid/CH₂Cl₂ mixed solvent. The conversion and the yield of epoxide are excellent. It was also found that [bis(acetoxy)iodo]benzene [PhI(OAc)₂] is a more efficient oxidant than PhIO. The catalyst in the ionic liquids can be recycled for several runs without substantial diminution in the catalytic activity.     

Aerobic epoxidation of olefins catalyzed by MgO–polysilazane–metal complexes

Co, Fe, Ni and Cu complexes of MgO‐supported polysilazane were prepared and found to be able to catalyze the aerobic epoxidation of long‐chain olefins to give corresponding epoxy‐alkanes in the presence of an aldehyde (as reductant) under mild conditions. When the Co complex catalyst was used for the aerobic oxidation of 1‐octene to give 1,2‐epoxy‐hexane, the yield and selectivity could achieve 92% and 100% respectively at 70 °C and under 1‐atm of O₂. The catalyst was very stable, and could be reused several times without any appreciable change in catalytic activity. Copyright © 1999 John Wiley & Sons, Ltd.     

Dehydrogenation of N-ethyl perhydrocarbazole catalyzed by PCP pincer iridium complexes: Evaluation of a homogenous hydrogen storage system

The iridium complexes IrH₂{C₆H₃-2,6-(CH₂PBu^t₂)₂ (1), IrH₂{C₆H₃-2,6-(CH₂PPrⁱ₂)₂ (2), and IrHCl{C₆H₃-2,6-(OPBu^t₂)₂ (3) have been found to be highly active catalysts for the dehydrogenation of N-ethyl perhydrocarbazole at 200 °C. However, dehydrogenation to the fully unsaturated ethyl carbazole does not occur in most instances. Complex 3 is the most active catalyst and shows reasonable activity even at 150 °C. No signs of dehydrogenation were found in experiments conducted at 100 °C. This apparently reflects the thermodynamic constraints imposed by the high enthalpy of dehydrogenation of the substrate.     

Theoretical and experimental investigations of the enantioselective epoxidation of olefins catalyzed by manganese complexes

The enantioselective epoxidation of olefin by Mn^II（R,R-PMCP）(OTf)2, H₂O₂ and H₂SO₄ was explored by DFT calculations and experiments. Theoretical results suggest that [MnV（O）(R,R-PMCP)（SO4）]+species with a triplet ground spin state serves as the active species for the olefin epoxidation. It can be generated by the H₂SO₄ assisted O-O heterolysis of Mn^III（OOH） species. Mn^III-persulfate is also involve...