Preparation of MCM-41 Supported Heterogenized Chiral Salen Mn (III) Complex and the Catalytic Activity in the Asymmetric Epoxidation

A chiral Manganese (III) salen complex was immobilized on the walls of MCM-41 (mobile crystalline material) through the multi-grafting method. The immobilized complex was characterized by XRD, FTIR, UV-Vis, ICP and Nitrogen sorption, and was applied to the asymmetric epoxidation of unfuctionalized alkenes including 1,2-dihydronaphthalene, α-methylstyrene, cis-β-methylstyrene, styrene using NaClO and m-chloroperbenzoic acid (m-CPBA) as oxidants respectively. The immobilized complex showed good activity and enantioselectivity in the epoxidation of 1,2-dihydronaphthalene by using NaClO as oxidant. It could also be run for 4 times in the epoxidation of α-methylstyrene without obvious loss of activity or enantiomeric excess.     

Silica Gel Anchored Chiral Mn(III)Salen Complexes for Enantioselective Epoxidation of Unfunctionalised Olefins

Heterogeneous Mn(III) chiral salen complexes are prepared through covalent attachment of salen ligand on silica gel via chloropropyl spacer and subsequent complexation with manganese. The complexes are well characterized by IR, UV/VIS, TGA and elemental analysis. Epoxidation of unfunctionalised prochiral olefins by Mn(III) chiral salen complexes using iodosobenzene and m-CPBA as the terminal oxidants and NMO as a co-oxidant was achieved with good yields albeit low enantiomeric excess.     

Immobilization of Dicationic Mn(III) Salen in the Interlayers of Montmorillonite Clay for Enantioselective Epoxidation of Nonfunctionalized Alkenes

Dicationic chiral Mn(III) salen complex (0.4 mol%) immobilized in the interlayer of montmorillonite clay 4A, epoxidize bulkier alkenes (epoxide yield 68–99%) with high chiral induction (up to 95% ee) with a catalyst reusability of up to four cycles.     

Chiral Salen Mn(III) Complex Axial Coordination Immobilized on Diamine Modified Alspp and Highly Efficient Large-Scale Epoxidation of Olefins as a Recoverable Catalyst

Aluminium oligo-styrenyl phosphonate-hydrogen phosphate (AlSPP) was used as organic–inorganic hybrid support after chloromethylation, and then with using different diamines as a reactive surface modifier. We realized the homogeneous chiral salen Mn(III) complex axially immobilized on modified AlSPP by a covalent grafting method. The prepared heterogeneous salen Mn(III) complexes were characterized by different techniques such as FT-IR, diffusion reflection UV–Vis, AAS, XPS, N₂ volumetric adsorption, SEM, TEM and TG. The chiral salen Mn(III) complexes were immobilized onto the AlSPP through axial coordination for the first time with m-CPBA/NMO as an oxidant system for asymmetric epoxidation of unfunctionalized olefins. The supported catalyst showed very good performance in the asymmetric epoxidation of α-methylstyrene and indene. The catalyst could be easily recovered and reused without significant loss of activity and enantioselectivity after nine cycles. This novel heterogeneous catalyst could be efficiently used in large-scale reactions with the enantioselectivity being maintained at the same level, which offer great possibilities for application in industry.     

无机材料固载手性Mn(Salen)催化剂的研究进展

针对不同无机材料载体和固载方法,综述了近几年无机材料固载Mn(Salen)催化剂的研究进展。重点介绍了二氧化硅、分子筛、活性炭、溶胶凝胶固载手性Mn(Salen)催化剂的特点及性能,并对固载手性Mn(Salen)催化剂存在的问题和前景进行了分析。     

Environment Friendly Protocol for Enantioselective Epoxidation of Non-Functionalized Alkenes Catalyzed by Recyclable Homochiral Dimeric Mn(III) Salen Complexes with Hydrogen Peroxide and UHP Adduct as Oxidants

Environment friendly oxidants e.g. H₂O₂ and anhydrous urea hydrogen peroxide adduct (UHP) epoxidize non-functionalized alkenes (epoxide yield 40–99%) with high enantioselectivity (up to 94% ee) in 4–15 h using two recyclable homochiral dimeric Mn(III) salen complexes in presence of PyN-oxide with the catalysts reusability several times when UHP was used as an oxidant.     

Oxidation of cyclohexane promoted by [Fe(III)(Salen)Cl] and [Mn(III)(Salen)Cl]

Salen complexes of iron(III) and manganese(III) were synthesized and employed as catalysts in the oxidation of cyclohexane, using hydrogen peroxide and tert–butylhydroperoxide. The reactions were carried out in acetonitrile at room temperature. The catalysts were characterized by infrared and Mössbauer spectroscopy, elemental analysis, conductivity and cyclic voltammetry. Conversions up to 10.2% (4.2% and 6.0% yields for cyclohexanol and cyclohexanone, respectively) were obtained for the system [Fe(III)(Salen)Cl]/tBuOOH.     

Poly(styrene) Resin‐Supported Cobalt(III) Salen Cyclic Oligomers as Active Heterogeneous HKR Catalysts

A cross‐linked poly(styrene) support functionalized with cobalt(III) salen cyclic oligomers that can be used as a catalyst for the hydrolytic kinetic resolution (HKR) of terminal epoxides is reported. This catalyst is the most active heterogeneous catalyst to date for the HKR of terminal epoxides and can be recycled more than six times with excellent enantioselectivities for the HKR of epichlorohydrin. A 3‐fold rate enhancement was observed when conducting the HKR reaction with 6 equivalents of water compared to 0.6 equivalents. We hypothesize that this rate enhancement is due to water sequestration of the diol product from the organic phase, thereby maintaining a high local concentration of epoxides and catalyst in the organic phase.     

Epoxidation of Olefins Catalyzed by Mn(II) Salen Complex Anchored on PAMAM–SiO2 Dendrimer

New dendritic catalysts have been prepared by the immobilization of a Mn(II) salen complex on a polyamidoamine dendrimer propagated on the surface of silica. These have been applied in the catalytic epoxidation of olefins. Although the increase of the amount of Mn loading is found to be limited on high-generation dendrimers, the Mn(II) salen complex anchored on the fourth-generation dendrimer shows much higher catalytic activity toward the epoxidation of styrene than that anchored on lower generations. These results suggest that the length of the dendritic backbone chain plays an important role in increasing the accessibility between the catalytic active sites of the immobilized Mn(II) salen complex and the reactant molecules, resulting in the enhancement of the catalytic activity of the Mn(II) salen complex anchored on the fourth-generation dendrimer.     

Molybdenum(VI) Amino Triphenolate Complexes as Catalysts for Sulfoxidation,Epoxidation and Haloperoxidation

Two molybdenum(VI) complexes bearing a C₃ symmetrical amino tris‐tert‐butylphenolate ligand have proved to be air‐ and water‐tolerant catalysts that efficiently catalyse, in high yields and selectivity, the oxidation of sulfides, olefins and halides. In particular high turnover frequencies and turnover numbers (TOF and TON) have been obtained for the cyclooctene epoxidation (catalyst loading down to 0.05%, TONs up to 88,000 and TOFs up to 7500 h⁻¹).     

Reusable Chiral Dicationic Chromium(III) Salen Catalysts for Aminolytic Kinetic Resolution of trans‐Epoxides

A series of new recyclable chiral dicationic chromium(III) salen complexes 1 – 10 bearing different substituents, viz., hydrogen, methyl, tert‐butyl, triphenylphosphinomethyl, triethylaminomethyl, methylimidazolium, methylpyridinium, methyl‐N,N‐dimethylpyridinium at the 3,3′‐ and 5,5′‐ positions of the salen unit with (1S,2S)‐(+)‐1,2‐diaminocyclohexane, (1S,2S)‐(−)‐1,2‐diphenyl‐1,2‐diaminoethane, and (S)‐(−)‐1,1′‐binaphthyl‐2,2′‐diamine collars have been synthesized and characterized by various physico‐chemical methods. These complexes were used as catalysts for the highly enantioselective aminolytic kinetic resolution of racemic trans‐epoxides with different anilines as nucleophiles at room temperature. With the use of catalyst 3 , anti‐β‐amino alcohols were obtained in excellent yields (>99% with respect to the nucleophile) and enantioselectivities (ee>99%) with the concomitant recovery of corresponding epoxides in high optical purity (ee up to >99%) and quantitative yields in 12 h. The catalyst 3 is recyclable in the aminolytic kinetic resolution process and worked well up to six cycles with retention of enantioselectivity.     

Anchoring of Chiral Manganese(III) Salen Complex onto Organo Clay and Porous Clay Heterostructure and Catalytic Activity in Alkene Epoxidation

The chiral Mn(III) salen complex (C1) was immobilised onto a natural clay (BEN) and a porous clay heterostructure (PCH) functionalised with 3-aminopropyltriethoxysilane (APTES). FTIR, XPS and Mn chemical analysis confirm the C1 anchorage in both materials, but with higher efficiency in BEN_APTES clay. The catalytic activity of C1@BEN_APTES and C1@PCH_APTES, was assessed in the epoxidation of styrene (sty) and ∝-methylstyrene (∝-Mesty) using NaOCl and m-chloroperoxybenzoic acid (m-CPBA)/N-methylmorpholine-N-oxide (NMO). Both materials behave as moderate catalysts, show high epoxide selectivity but low enantiomeric excesses. In the case of sty epoxidation with m-CBPA/NMO the C1@PCH_APTES catalyst showed the highest catalytic activity, whereas in ∝-Mesty epoxidation, the C1@PCH_APTES catalyst, although leading to lower substrate conversion than the BEN analogue, presented the lowest complex leaching. In all cases, the oxidant NaOCl had some destructive effect in the hybrid catalysts, highlighting the importance of a careful choice of catalyst and oxidant system.     

Asymmetric Epoxidation of Olefins by Manganese(III) Complexes Stabilised on Nanocrystalline Magnesium Oxide

The asymmetric epoxidation of unfunctionalised olefins to epoxides is realised by using manganese(III) complexes stabilised on nanocrystalline magnesium oxide in the presence (1R,2R)‐(−)‐diaminocyclohexane as a chiral ligand in good yields and up to 91 % enantiomeric excess.     

Mn(Salen)/A1-HMS催化剂微波固相法制备及其催化性能

采用新的微波固相法制备出Mn(Salen)/Al-HMS催化剂.通过FTIR和TG的表征,结果表明,微波固相方法成功地将Mn(Salen)配合物固载于介孔Al-HMS分子筛中.以苯乙烯环氧化反应为例比较了不同方法制备的催化剂的催化性能,发现微波固相法制备的Mn(Salen)/Al-HMS-IP催化剂具有较高的催化活性和最好的环氧化物选择性,此外,考察了催化剂性能还与制备过程中的微波辐射时间、反应时间、反应溶剂、反应温度、氧化剂的用量及催化剂的重复使用对微波固相法制备的催化剂的性能影响规律,得到了满意的结果.     

Novel homogeneous Salen Mn(III) catalysts synthesized from dialdehyde or diketone with o-aminophenol for catalyzing epoxidation of alkenes

A series of novel non-salicylaldehyde based Salen ligands have been synthesized from the condensation of dialdehyde or diketone with o-aminophenol and the corresponding manganese(III) complexes prepared by further coordination of them with . FT-IR, UV–Vis spectra, chemical analysis and the structure optimized by Hartree-Fork/3-21G+ all indicated that the qualities of these novel Mn complexes were relative to their molecular structures. More specifically, glyoxal based Mn complex 2c, which was similar to the traditional Mn(III)-salicylethylenediamine, had a short carbon chain and non geometrical constraint of the aliphatic bridge in the two o-aminophenol, and its quality was the best when compared to glutaraldehyde, 2,4-pentanedione and 1,3-cyclohexanedione based Salen Mn(III) complexes (3c, 4c and 5c). And it was also the excellent catalyst for the epoxidations of several non-functionalized alkenes with molecular oxygen/sacrificial-isobutyaldehyde, PhI(OAc)₂ or H₂O₂ as oxidant.     

Mn（Salen）／Al-HMS催化剂微波固相法制备及其催化性能

采用新的微波固相法制备出Mn(Salen)/Al-HMS催化剂。通过FT IR和TG的表征,结果表明,微波固相方法成功地将Mn(Salen)配合物固载于介孔Al-HMS分子筛中。以苯乙烯环氧化反应为例比较了不同方法制备的催化剂的催化性能,发现微波固相法制备的Mn(Salen)/Al-HMS-IP催化剂具有较高的催化活性和最好的环氧化物选择性,此外,考察了催化剂性能还与制备过程中的微波辐射时间、反应时间、反应溶剂、反应温度、氧化剂的用量及催化剂的重复使用对微波固相法制备的催化剂的性能影响规律,得到了满意的结果。     

手性金属络合物催化剂在不对称合成中的应用

不对称合成是当前有机合成中热门研究领域，利用手性金属络合物催化剂催化不对称硅氢化、烷基化，以烯烃、酮、亚胺、醛等合成手性醇、手性胺、手性酮等具有很好的工业应用前景。本文论述了手性金属络合物催化剂在不对称硅氢化反应及其在二烷基锌对醛的不对称烷基化反应中的应用。     

Asymmetric Epoxidation of Chromenes Using Manganese(III) Complexes with Novel Chiral Salen-like Schiff Base Ligands

Abstract  

Three novel chiral salen-like schiff base ligands and their Mn(III) complexes containing different amino acid unit have been synthesized and characterized. Asymmetric epoxidation reactions show these complexes are effective catalysts for the chromenes with buffer NaOCl as terminal oxidant and pyridine N-oxide as co-catalyst in the presence of ionic liquid. Good-to -excellent enantioselectivity and acceptable yields can be obtained under optimum reaction conditions. Catalyst 4c gives the highest ee (95%) for 6-chloro-2,2-dimethylchromene among these catalytic performances. Furthermore, compared the enantioselectivity of catalyst 4c with the other two catalysts 4a and 4b, the positive experimental results suggest that the steric effect of the ligands plays an important role in the asymmetric catalysis.