N,N′-Bis(3,5-di-t-butylsalicylidene)-1,2-cyclohexanediamino-manganese(III) chloride – the Jacobsen catalyst

The commercially available Jacobsen catalyst, N,N′-Bis(3,5-di-t-butylsalicylidene)-1,2-cyclohexanedi-aminomanganese(III) chloride 2 , is the most enantioselective catalyst developed to date for the asymmetric epoxidation of a broad range of unfunctionalized olefins. After describing the synthesis of the title compound a brief discussion of the epoxidation mechanism is given. Afterwards several applications for the enantioselective epoxidation of unfunctionalized olefins are described. For each application the scope and limitations are discussed     

Dioxirane oxidation of 3β-substituted Δ<Superscript>5</Superscript>-steroids

This article reviews the utility of dioxiranes in the oxidation of 3beta-substituted delta5-sterols. Dioxiranes are the smallest cyclic peroxides that contain a carbon atom. They can be generated in situ from Oxone (2KHSO5.KHSO4.K2SO4) and a ketone. Dioxiranes are versatile oxidizing agents. The most common reaction of dioxiranes is epoxidation, with nearly 1:1 ratios of alpha/beta isomer products in all cases. delta5-Steroids with different side chains were epoxidized by dioxiranes generated in situ from several commercially available ketones. Although ketones function as catalyst, they were used in about an equivalent amount or large excess to accelerate the reaction.     

钼基催化剂在烯烃液相环氧化反应中的应用研究进展

介绍了钼络合物催化剂、固载化的钼络合物催化剂及MoO₃基的固体钼催化剂在烯烃液相环氧化反应中的应用。以有机过氧化物为氧化剂时,不同的钼基催化剂均表现出很好的催化性能,其中络合物中的配体对其催化性能有很大影响,并且可以通过引入手性配体实现对烯烃的不对称环氧化,而固体钼催化剂的性能则与载体上钼物种的种类密切相关。但绝大多数钼催化剂对H₂O₂参与的环氧化反应没有活性,开发对H₂O₂有催化活性的钼基催化剂是一个重要的研究方向。     

金属卟啉催化烯烃不对称环氧化反应的研究

合成了5种简单金属卟啉锰配合物，并以这5种金属卟啉作为催化剂，以手性季铵盐为手性相转移催化剂，研究催化烯烃不对称环氧化反应。结果表明：金属卟啉锰中苯环上的不同取代基对烯烃环氧化速度有较大的影响；手性相转移催化剂的加入，不仅提高了反应速度，而且对烯烃的环氧化起到了一定的不对称诱导作用；不同底物的烯烃，不对称环氧化反应对映选择性不同。     

EPOXIDATION OF FUNCTIONALIZED OLEFINS OVER SOLID CATALYSTS

Heterogeneous catalytic epoxidation of functionalized olefins in the liquid phase has been reviewed, focusing on catalyst performance and its interrelation with the crucial parameters of the catalytic systems. Efficient catalysts include supported and mixed oxides, framework-substituted (“redox”) molecular sieves, layered-type materials, heterogenized homogeneous catalysts, and some others. Among the various substrates, allylic and homoallylic alcohols, and unsaturated carbonyl compounds have received most attention so far. The great variety of available catalysts enables selective epoxidation of most substituted olefins. The mechanistic understanding of heterogeneous catalytic epoxidation is still underdeveloped, rendering catalyst design rather empirical. A considerable potential for future development lies in the area of “heterogenization” of successful homogeneous catalysts especially for asymmetric epoxidation. Crucial requirements in the development of heterogeneous catalytic epoxidation catalysts are, besides good catalytic performance and cheap oxidant, recyclability and resistance to leaching of the active component. Some of the examples shown in the literature do not fulfill the latter requirement.     

EPOXIDATION OF FUNCTIONALIZED OLEFINS OVER SOLID CATALYSTS

Heterogeneous catalytic epoxidation of functionalized olefins in the liquid phase has been reviewed, focusing on catalyst performance and its interrelation with the crucial parameters of the catalytic systems. Efficient catalysts include supported and mixed oxides, framework-substituted (“redox”) molecular sieves, layered-type materials, heterogenized homogeneous catalysts, and some others. Among the various substrates, allylic and homoallylic alcohols, and unsaturated carbonyl compounds have received most attention so far. The great variety of available catalysts enables selective epoxidation of most substituted olefins. The mechanistic understanding of heterogeneous catalytic epoxidation is still underdeveloped, rendering catalyst design rather empirical. A considerable potential for future development lies in the area of “heterogenization” of successful homogeneous catalysts especially for asymmetric epoxidation. Crucial requirements in the development of heterogeneous catalytic epoxidation catalysts are, besides good catalytic performance and cheap oxidant, recyclability and resistance to leaching of the active component. Some of the examples shown in the literature do not fulfill the latter requirement.     

Synthetic applications of nonmetal catalysts for homogeneous oxidations

Nonmetal oxidation catalysts have gained much attention in recent years. The reason for this surge in activity is 2-fold: On one hand, a number of such catalysts has become readily accessible; on the other hand, such catalysts are quite resistant toward self-oxidation and compatible under aerobic and aqueous reaction conditions. In this review, we have focused on five nonmetal catalytic systems which have attained prominence in the oxidation field in view of their efficacy and their potential for future development; stoichiometric cases have been mentioned to provide overview and scope. Such nonmetal oxidation catalysts include the alpha-halo carbonyl compounds 1, ketones 2, imines 3, iminium salts 4, and nitroxyl radicals 5. In combination with a suitable oxygen source (H2O2, KHSO5, NaOCl), these catalysts serve as precursors to the corresponding oxidants, namely, the perhydrates I, dioxiranes II, oxaziridines III, oxaziridinium ions IV, and finally oxoammonium ions V. A few of the salient features about these nonmetal, catalytic systems shall be reiterated in this summary. The first class entails the alpha-halo ketones, which catalyze the oxidation of a variety of organic substrates [figure: see text] by hydrogen peroxide as the oxygen source. The perhydrates I, formed in situ by the addition of hydrogen peroxide to the alpha-halo ketones, are quite strong electrophilic oxidants and expectedly transfer an oxygen atom to diverse nucleophilic acceptors. Thus, alpha-halo ketones have been successfully employed for catalytic epoxidation, heteroatom (S, N) oxidation, and arene oxidation. Although high diastereoselectivities have been achieved by these nonmetal catalysts, no enantioselective epoxidation and sulfoxidation have so far been reported. Consequently, it is anticipated that catalytic oxidations by perhydrates hold promise for further development, especially, and should ways be found to transfer the oxygen atom enantioselectively. The second class, namely, the dioxiranes, has been extensively used during the last two decades as a convenient oxidant in organic synthesis. These powerful and versatile oxidizing agents are readily available from the appropriate ketones by their treatment [figure: see text] with potassium monoperoxysulfate. The oxidations may be performed either under stoichiometric or catalytic conditions; the latter mode of operation is featured in this review. In this case, a variety of structurally diverse ketones have been shown to catalyze the dioxirane-mediated epoxidation of alkenes by monoperoxysulfate as the oxygen source. By employing chiral ketones, highly enantioselective (up to 99% ee) epoxidations have been developed, of which the sugar-based ketones are so far the most effective. Reports on catalytic oxidations by dioxiranes other than epoxidations are scarce; nevertheless, fructose-derived ketones have been successfully employed as catalysts for the enantioselective CH oxidation in vic diols to afford the corresponding optically active alpha-hydroxy ketones. To date, no catalytic asymmetric sulfoxidations by dioxiranes appear to have been documented in the literature, an area of catalytic dioxirane chemistry that merits attention. A third class is the imines; their reaction with hydrogen peroxide or monoperoxysulfate affords oxaziridines. These relatively weak electrophilic oxidants only manage to oxidize electron-rich substrates such as enolates, silyl enol ethers, sulfides, selenides, and amines; however, the epoxidation of alkenes has been achieved with activated oxaziridines produced from perfluorinated imines. Most of the oxidations by in-situ-generated oxaziridines have been performed stoichiometrically, with the exception of sulfoxidations. When chiral imines are used as catalysts, optically active sulfoxides are obtained in good ee values, a catalytic asymmetric oxidation by oxaziridines that merits further exploration. The fourth class is made up by the iminium ions, which with monoperoxysulfate lead to the corresponding oxaziridinium ions, structurally similar to the above oxaziridine oxidants except they possess a much more strongly electrophilic oxygen atom due to the positively charged ammonium functionality. Thus, oxaziridinium ions effectively execute besides sulfoxidation and amine oxidation the epoxidation of alkenes under catalytic conditions. As expected, chiral iminium salts catalyze asymmetric epoxidations; however, only moderate enantioselectivities have been obtained so far. Although asymmetric sulfoxidation has been achieved by using stoichiometric amounts of isolated optically active oxaziridinium salts, iminium-ion-catalyzed asymmetric sulf-oxidations have not been reported to date, which offers attractive opportunities for further work. The fifth and final class of nonmetal catalysts concerns the stable nitroxyl-radical derivatives such as TEMPO, which react with the common oxidizing agents (sodium hypochlorite, monoperoxysulfate, peracids) to generate oxoammonium ions. The latter are strong oxidants that chemoselectively and efficiently perform the CH oxidation in alcohols to produce carbonyl compounds rather than engage in the transfer of their oxygen atom to the substrate. Consequently, oxoammonium ions behave quite distinctly compared to the previous four classes of oxidants in that their catalytic activity entails formally a dehydrogenation, one of the few effective nonmetal-based catalytic transformations of alcohols to carbonyl products. Since less than 1 mol% of nitroxyl radical is required to catalyze the alcohol oxidation by the inexpensive sodium hypochlorite as primary oxidant under mild reaction conditions, this catalytic process holds much promise for future practical applications.     

联萘酚纳米孔道配位聚合物催化剂的研究进展

纳米多孔材料可用作催化剂、气体储存材料和光电子器件,是目前新型多孔材料的研究热点之一。手性联萘酚配体所修饰的催化剂是一种很优异的C2轴对称手性诱导源,可以催化各种α,β-不饱和羰基化合物,具有良好的催化活性和对映选择性。本文对由手性联萘酚类配体所修饰的小分子催化剂、聚合物负载的催化剂和自负载催化剂,在不饱和羰基化合物催化不对称环氧化反应中的应用进行了综述。本文介绍了对手性联萘酚纳米多孔配位聚合物的研究。     

Optimisation of olefin epoxidation catalysts with the application of high-throughput and genetic algorithms assisted by artificial neural networks (softcomputing techniques)

An olefin epoxidation Ti catalyst has been optimised by means of high-throughput experimentation involving materials synthesis, postsynthesis treatments, and catalytic testing. Softcomputing techniques for advanced experimental design have been used. The variables explored in the hydrothermal synthesis of Ti-silicate-based catalysts were: concentration of OH⁻, titanium, and surfactant. The probe reaction employed for the optimisation was the solvent-free epoxidation of cyclohexene, with tert-butylhydroperoxide as oxidant. The different catalyst groups detected by clustering analysis were studied by XRD and UV diffuse reflectance. Ti-mesoporous MCM-41 and MCM-48 molecular sieves were among the most active catalysts. The best performing catalysts were tested for epoxidation of different linear olefins.     

Catalytic Asymmetric Epoxidation of Unfunctionalized Olefins by Supported Cu(II)-Amino Acid Complexes

Polymer-supported Cu(II) complexes with L-phenyl alanine and L-valine were used as chiral catalysts for asymmetric epoxidation of nonfunctionalized straight-chain terminal olefins viz. 1-octene, 1-hexene, 2-methyl-1-pentene and 4-methyl-1-pentene using m-chloroperbenzoic acid (m-CPBA) as oxidant giving high conversions and selectivity. Enantiomeric yields, though moderate, are comparable with the best-reported ees using homogeneous catalysts. All catalysts displayed good recycling efficiency. Variations in percent ee have been discussed on the basis of the structural geometry of the supported catalysts and the trajectory of the olefin approach to the active oxo-intermediate.     

杂多化合物催化剂在精细化工合成中的应用

本文综术了杂多化合物作为酸催化剂，催化烷基化和去烷基化反应、缩聚反应、水合和失水、酯化和醚化反应；以及作为氧化催化剂，在烯烃、芳烃、酚的氧化和环氧化反应中的应用。表面杂多化合物作为催化剂在合成精细化学中有广泛的应用价值。     

氯乙酸异丙酯复合催化合成研究

以氯乙酸与异丙醇为原料,采用结晶硫酸高铈/硫酸氢钾复合催化剂,催化合成氯乙酸异丙酯.研究了不同助催化剂、催化剂配比和用量对其合成反应的影响,优化了醇酸比、催化剂用量、反应时间等反应条件,并且考察了复合催化剂的重复使用性.结果表明,以结晶硫酸高铈/硫酸氢钾为复合催化剂的效果最好,其最适宜反应条件为:n(醇)/n(酸)为1...     

Mass‐Spectrometric and Kinetic Studies on the Mechanism and Degradation Pathways of Titanium Salalen Catalysts for Asymmetric Epoxidation with Aqueous Hydrogen Peroxide

The composition and degradation of a highly active and enantioselective titanium salalen in situ catalyst for the asymmetric epoxidation of olefins with aqueous hydrogen peroxide was investigated. Kinetic data and ESI‐MS studies point to a mononuclear titanium salalen as the catalytically active species. By means of ESI‐MS and selective monodeuteration of the salalen ligand, the oxidative degradation was studied. Upon exposure to aqueous hydrogen peroxide, the amine functionality of the salalen ligand is converted to the hydroxylamine, followed by loss of water and generation of the inactive titanium‐salen complex. This transformation limits the activity of the catalyst in the epoxidation of less electron‐rich olefins, such as 1‐octene.     

烯烃环氧化催化剂的研究进展

由于烯烃环氧化物在多领域的广泛应用,人们在烯烃的环氧化反应方面做了大量的工作.反应催化剂的研究无疑是工作的重中之重,因为绝大部分的烯烃环氧化反应都是需要催化剂来催化的.均相催化剂由于其不易分离、无法回收、流出液难于处理客易造成污染等缺点,不较多相催化剂研究的少.作者将主要从催化剂方面,尤其是多相催化方面介绍一下烯烃环氧化的研究进展.     

Non‐Heme Manganese Complexes Catalyzed Asymmetric Epoxidation of Olefins by Peracetic Acid and Hydrogen Peroxide

Chiral non‐heme aminopyridine manganese complexes catalyze the enantioselective epoxidation of olefins with peracetic acid or hydrogen peroxide with moderate to high yields and ee valuess up to 89% (peracetic acid, AcOOH) and 84% (hydrogen peroxide, H₂O₂), performing as many as 1000 turnovers.     

Asymmetric epoxidation of unfunctionalized olefins catalyzed by Mn(III) salen complex immobilized on MCM-48

Chiral Mn(III) salen complexes were supported on mesoporous molecular sieve MCM-48 and employed as catalyst in the asymmetric epoxidation of some unfunctionalized olefins. The as-synthesized catalysts showed excellent enantioselectivity than homogeneous catalysts for α-methylstyrene and the highest ee value (up to >99%) was obtained. Furthermore, these catalysts were also effective for bulkier olefins such as indene and 1-phenylcyclohexene. Compared to homogeneous counterparts, the heterogeneous catalysts are more stable and can be recycled three times without loss of enantioselectivity.     

Synthesis of layered crystalline AlSPP and its immobilized chiral salen Mn(III) catalysts applicated in the large scale asymmetric epoxidation of olefins

Chiral salen Mn(III) complex was axially immobilized onto phenoxy-modified organic polymer-inorganic hybrid material layered crystalline aluminium oligo-styrenyl phosphonate-hydrogen phosphate. The prepared catalysts exhibited excellent activities and enantioselectivities for asymmetric epoxidation of unfunctionalized olefins with m-chloroperbenzoic acid as oxidant, especially for the epoxidation of α-methylstyrene (conversion: up to 99 %; ee: exceed 99 %). A point worth emphasizing is that the heterogeneous catalysts afforded remarkable increases of conversions and ee values without adding axial base N-methylmorpholine N-oxide for the asymmetric epoxidation of olefins. The catalyst can be easily recovered and reused with slightly decrease of activity and enantioselectivity after seven cycles. Delightedly, this novel heterogeneous catalyst could also be efficiently used in large-scale reactions with the enantioselectivity being maintained at the same level, which provided the potentiality for application in industry.     

杂原子掺杂beta分子筛的烯烃环氧化催化性能

采用液-固相同晶取代法分别制备了W、Mo、V和Ti掺杂的四种杂原子beta分子筛,并以环己烯和环辛烯为探针底物分子,系统性评价了W-beta、Mo-beta、V-beta和Ti-beta催化烯烃环氧化反应性能。结果表明,所制备的四种杂原子beta分子筛均具有较高的结晶度,且完好继承了母体Al-beta分子筛的微孔结构与纳米颗粒形貌;由于离子半径和M—O键长的差异,W和Mo的骨架掺入量相对较低,V和Ti的掺入量相对较高;催化烯烃环氧化反应中,有限的活性金属含量导致W-beta和Mo-beta催化环烯烃的转化率低于V-beta和Ti-beta,但W-beta、Mo-beta、V-beta的反应转换频率（TOF）较高,说明W、Mo、V金属位点的活性更高;催化环己烯环氧化反应中,V-beta催化剂易引发烯丙基氧化副反应,环氧化物选择性低于其他三种催化剂,且V活性组分氧化物形态含量较高,反应过程中易脱落,导致V-beta催化剂循环再生性能较差;Ti掺杂beta催化剂表现出最佳的烯烃环氧化反应性能,提高Ti含量可有效提高反应转化率,但骨架Ti掺入量存在极值,过多的Ti物种趋向于氧化物形态,降低反应活性（TOF值）,因此适宜的骨架Ti掺杂有利于Ti-beta分子筛催化烯烃环氧化反应。     

The epoxidation of cyclohexene by dioxiranes over ketone catalysts

In this work, the dioxirane system has been applied to the epoxidation of cyclohexene. The catalytic activity of acetone, butan-2-one and pentan-2-one presented as homogeneous catalysts or supported on inorganic and polymer materials was investigated. It was found that the rate of cyclohexene oxide formation increased in proportion to increasing ketone concentrations using acetone and butan-2-one. Because of the advantages of supported catalysts, ketones were chemisorbed or grafted onto a range of different supports including different forms of silica and various polymers. The presence of carbonyl groups on the surface of the supports was confirmed and their catalytic activity was evaluated. The turnover frequency of the grafted ketones were compared with that of the homogeneous catalysts and design criteria for the further development of supported ketone catalysts were established.     

Effect of pore size on the performance of mesoporous material supported chiral Mn(III) salen complex for the epoxidation of unfunctionalized olefins

A series of mesoporous MCM-41 and MCM-48 materials with different pore sizes were synthesized and used as supports to immobilize chiral Mn(III) salen complex. The heterogeneous catalysts were characterized by XRD, FT-IR, DR UV–vis, and N₂ sorption, and the results indicated the successful immobilization of chiral Mn(III) salen complex. The confinement effect of pore size on the catalytic performance of the heterogeneous catalysts was studied for the asymmetric epoxidation of unfunctionalized olefins with m-chloroperoxybenzoic acid as an oxidant. It was found that the conversions and enantiomeric excess (ee) values were closely correlated with the pore sizes of parent supports. The catalysts immobilized on the large-pore mesoporous supports exhibited higher conversions, and for the catalysts immobilized on MCM-41 materials, the ee values improved with increasing pore size. However, for the MCM-48 material-supported catalysts, the compatible pore size of the support with the substrate was beneficial for obtaining higher enantioselectivity in olefin epoxidation.