Epoxidation Of Unfunctionalized Olefins Research Articles

Retraction: Synthesis of a novel type of chiral salen Mn(iii) complex immobilized on crystalline zinc poly(styrene-phenylvinylphosphonate)-phosphate (ZnPS-PVPP) as effective catalysts for asymmetric epoxidation of unfunctionalized olefins

Retraction for ‘Synthesis of a novel type of chiral salen Mn(iii) complex immobilized on crystalline zinc poly(styrene-phenylvinylphosphonate)-phosphate (ZnPS-PVPP) as effective catalysts for asymmetric epoxidation of unfunctionalized olefins’ by Jing Huang et al., Catal. Sci. Technol., 2011, 1, 1472–1482, DOI: 10.1039/C1CY00285F

Retraction: A series of novel types of immobilized chiral salen Mn(iii) on different organic polymer–inorganic hybrid crystalline zinc phosphonate–phosphate act as catalysts for asymmetric epoxidation of unfunctionalized olefins

Retraction for ‘A series of novel types of immobilized chiral salen Mn(iii) on different organic polymer–inorganic hybrid crystalline zinc phosphonate–phosphate act as catalysts for asymmetric epoxidation of unfunctionalized olefins’ by Jing Huang et al., Catal. Sci. Technol., 2012, 2, 1040–1050, DOI: 10.1039/C2CY00502F.

Mechanistic Investigation on Oxygen Transfer with the Manganese‐Salen Complex

AbstractThe best‐known application of salen complexes is the use of a chiral ligand loaded with manganese to form the Jacobsen complex. This organometallic catalyst is used in the epoxidation of unfunctionalized olefins and can achieve very high selectivities. Although this application was proposed many years ago, the mechanism of oxygen transfer remains a question until now. In this paper, the epoxidation mechanism is investigated by an ab initio kinetic modeling study. First of all a proper DFT functional is selected that yields the correct ordering of the various spin states. Our results show that the epoxidation proceeds via a radical intermediate. If we start from the radical intermediate, these results can explain the experiments with radical probes. The subtle influences in the transition state using the full Jacobsen catalyst explain the product distribution observed experimentally.

The enantioselectivity of the manganese-salen complex in the epoxidation of unfunctionalized olefins and the influence of grafting

Jacobsen’s complexes are famous for their usability for enantioselective epoxidations. However, the applicability of this catalytic system has been severely limited by several practical problems such as deactivation and separation after reaction. Grafting of Jacobsen-type complexes on solid supports is an attractive way to overcome these problems but led to a decrease in selectivity. A combined theoretical and experimental approach is presented to unravel the factors governing enantioselectivity. The importance of different substituents was determined by analyzing the transition state for the oxygen transfer using the full system as a model. An analysis of the asymmetric complex has shown an inherent tendency for a decreased selectivity due to the lack of specific bulky groups. Experimentally an immobilized Jacobsen catalyst on a metal organic framework (MIL-101) was synthesized which confirms the computational tendencies but the decrease in selectivity is limited, indicating that the MIL-101(Cr) is a suitable carrier for this complex.

A Homogeneous Chiral Manganese(III)–Salphe Catalyst for Enantioselective Epoxidation of Olefins

A new chiral Mn(III)–Salphe catalyst was synthesized from natural amino acid (R)-phenylalanine and 3,5-di-tert-butyl-hydroxybenzaldehyde and applied to the asymmetric epoxidations of unfunctionalized olefins in ionic liquids. Satisfactory enantioselectivities (79% < ee < 93%) and good yields were achieved when NaClO was used as oxidant. We found that both the pH value (11.3) and reaction temperature (15 °C) were crucial for the epoxidation reactions. In our reaction system, NH4OAc was unnecessary. We proposed that alcoholic hydroxyls in the Mn(III)–Salphe compound played the role of axial ligand. However, the reaction time was longer than when using Jacobsen's catalyst because of the structure of the Mn(III)–Salphe compound, in which coordination geometries by the two alcoholic hydroxyls with certain angles affected the substrate approaching the Mn(V) = 0 center. The chiral ligand was characterized by the combination of infrared, ultraviolet, and visible spectra and 1H NMR. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.

Enantioselective epoxidation of nonfunctionalized alkenes catalyzed by recyclable new homochiral bis-diamine-bridged bi-Mn(salen) complexes

Three new homochiral bis-diamine-bridged bi-Mn(salen) complexes were synthesized. Their catalysis on asymmetric epoxidation of α-methylstyrene, styrene and indene was studied with NaClO and m-CPBA as oxidants respectively. This homogeneous catalyst exhibited comparable catalytic activity and enantioselectivity to the Jacobsen’s catalyst in the asymmetric epoxidation of unfunctionalized olefins. Furthermore, the catalyst could be conveniently recovered and reused at least five times without significant losses of both activity and enantioselectivity. Specially, it also could be efficiently used in large-scale reactions with superior catalytic disposition being maintained at the same level, which provided the potential for the applications in industry. The effect of axial bases, temperature and solvent on activity and enantioselectivity of the catalytic system were also studied.

Asymmetric Epoxidation Using Iminium Salt Organocatalysts Featuring Dynamically Controlled Atropoisomerism

Introduction of a pseudoaxial substituent at a stereogenic center adjacent to the nitrogen atom in binaphthyl- and biphenyl-derived azepinium salt organocatalysts affords improved enantioselectivities and yields in the epoxidation of unfunctionalized alkenes. In the biphenyl-derived catalysts, the atropoisomerism at the biphenyl axis is controlled by the interaction of this substituent with the chiral substituent at nitrogen.

The advance in asymmetric epoxidation of olefins catalyzed by chiral Mn(salen)

The chiral Mn (Ⅲ) salen complexes have proven to be the most effective catalyst for asymmetric epoxidation of unfunctionalized olefins, which are highly significant in the pharmaceutical, agrochemical and spice fields to synthesize chiral building blocks that could be transformed into other useful chiral compounds through regioselective ring-opening reactions or by the selective transformation of functional groups. This paper reviews the homogeneous chiral Mn (salen) catalyst and the heterogeneous chiral Mn (salen) catalysts which immobilized onto organic polymer, inorganic support and organic polymer-inorganic hybrid materials catalyzed enantioselectivity epoxidation reactions of unfunctional olefins

Retracted Article: Synthesis of a novel type of chiral salen Mn(iii) complex immobilized on crystalline zinc poly(styrene-phenylvinylphosphonate)-phosphate (ZnPS-PVPP) as effective catalysts for asymmetric epoxidation of unfunctionalized olefins

The hypothesized structure of ZnPS-PVPP (a) signifies that the two or more neighboring –PO3H2 groups are in same colloidal precipitation; while (b) signifies that the two neighboring –PO3H2 groups are in different colloidal precipitation.

ChemInform Abstract: Alkene Aziridination and Epoxidation Catalyzed by Chiral Metal Salen Complexes.

Abstract New chiral metal salen complexes substituted in the 3 position with bulky silyl groups (TMS, TBDMS) have been synthesized. Although some of these complexes catalyzed the epoxidation of unfunctionalized olefins in moderate to high ee's, they catalyzed the aziridination of cis-β-methylstyrene without any asymmetric induction.

ChemInform Abstract: Asymmetric Epoxidation of Unfunctionalized Alkenes with Ammonium and Phosphonium Monopersulfates Catalyzed by Chiral Mn(III)-Salen Complexes.

ChemInform Abstract: Asymmetric Epoxidation of Unfunctionalized Alkenes with Ammonium and Phosphonium Monopersulfates Catalyzed by Chiral Mn(III)-Salen Complexes.

Zirconium phosphonates-supported chiral Mn (III) Salen complexes for the asymmetric epoxidation of unfunctionalized olefins

Abstract The mesoporous zirconium phosphonates-supported Mn (III) Salen complexes ( 1a–e ) with the different lengths of alkylsulfonic linkage ( n = 2–6) and the loading amount of 0.041–0.059 mmol g −1 (based on Mn) were prepared and used as heterogeneous catalysts in the asymmetric epoxidation of styrene, α-methylstyrene and indene. The ee values significantly increased with the linkage length ( n ) from 2 to 6 only in the case of indene with the m- CPBA/NMO as an oxidant system, in all other shown cases the ee values are not significantly influenced by the linkage length ( n ). In m -CPBA/NMO system, the comparable ee values to the homogeneous Mn (III) Salen complex 1 were achieved. Due to the confined effect originating from the nanopores of zirconium phosphonates, the heterogeneous Mn (III) Salen complexes ( 1a–e ) gave twice (84–88%ee) as many as ee values of homogeneous Mn (III) Salen complex 1 (49%ee) in the NaClO/PPNO system.

Highly efficient asymmetric epoxidation of alkenes with a novel chiral complex of ruthenium(III) containing a sugar based ligand and triphenylphosphines

Mixed-ligand complexes of ruthenium(III) containing tridentate chiral Schiff-base ligands (H 2TDL *s) derived from condensation of either d-glucose amine or l-alanine with 3,5-di-tertiarybutylsalicyldehyde, and triphenylphosphine (PPh 3) or 2,2′-bipyridine (bipy) have been synthesized. The ruthenium(III)-complexes, [ R u III Cl ( TD L 1 * ) ( PP h 3 ) 2 ] {( H 2 TD L 1 * = N - 3 , 5 -di- ( tertiarybutyl ) salicylidine- d -glucosamine )},( 1) [ R u III Cl ( TD L 2 * ) ( PP h 3 ) 2 ] H 2 TD L 2 * = { N - 3 , 5 -di- ( tertiarybutyl ) salicylidine- l -alanine } ( 2) and [ R u III ( TD L 2 * ) ( bipy ) H 2 O ] Cl (bipy = 2,2′-bipyridine) ( 3) were characterized by analytical, spectral (UV–vis and IR), molar conductivity, magnetic moment and electrochemical studies. Complex 1 exhibited remarkable enantioselcetivity toward epoxidation of unfunctionalized alkenes using tert-butylhydroperoxide ( t-BuOOH) as terminal oxidant. Styrene, 4-chlorostyrene, 4-methylstyrene, 4-methoxystyrene, 1-methylcyclohexene and 1,2-dihydronaphthalene were effectively converted to their organic epoxides in the 70–95% ee at ambient temperature. A lesser enantioselectivity was observed when complexes 2 and 3 were used in the epoxidation of enlisted alkenes under identical experimental conditions. A mechanism involving intermediacy of a high-valent Ru(V)-oxo species is proposed for the catalytic epoxidation process.

Epoxidation of unfunctionalized olefins by Mn(salen) catalyst using organic peracids as oxygen source: a theoretical study.

The mechanism and origin of asymmetric induction in the Mn(III)(salen)-catalyzed epoxidation by peracetic acid have been elucidated by the density functional [Becke three-parameter hybrid functional combined with Lee-Yang-Parr correlation functional (B3LYP)] method in two different regimes: with and without an axial ligand. The acylperoxo complexes of Mn(II,III,IV) in cisON cisNO and trans geometrical configurations cannot compete with the catalyst-free Prilezhaev epoxidation. Instead, oxo species perform epoxidation following the O-O bond cleavage in the acylperoxo complexes. The epoxidation may proceed in a concerted and/or radical-mediated stepwise manner. The actual mechanism of the epoxidation depends on the electronic and oxidation state of the oxo species and the nature of the axial ligand. The olefin can approach the reactive MnO fragment of both cis and trans-l-isomers of the plain oxo species along multiple distinct directions: native approaches. The native approaches are used to rationalize the inversion of the absolute configuration of the product epoxide due to the axial ligand.

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.

Experimental and theoretical study on the reactivity of the R-CN/H2O2 system in the epoxidation of unfunctionalized olefins

A study on the reactivity of peroxycarboximidic acids in situ generated from acetonitrile, trichloroacetonitrile, benzonitrile, m-chlorobenzonitrile, 3-cyanopyridine, 1-naphthonitrile and 9-anthracenenitrile was performed by semiempirical AM1 method and experimentally in the epoxidation of cyclohexene and R-(+)-limonene. Experimental results showed that the reactivity of Cl3CCN/H2O2 was quite similar to MCPBA in the epoxidation of unfunctionalized olefins when a biphasic mixture CH2Cl2/H2O was employed as solvent.

2.2]- para-Cyclophane-4-carbaldehyde as building-block for chiral ligands : Part II: Epoxidation of alkenes catalyzed by the Mn(III)-complex of an atropoisomerically pure ( α, β, α, β)-tetraarylporphyrin

The synthesis of the Mn(III)-complex of the new enantiopure, atropoisomerically pure chiral porphyrin ( α, β, α, β)- 1 is described. The compound was used as the catalyst in the epoxidation of unfunctionalized olefins using aqueous NaOCl, 30%-H 2O 2 or PhIO as oxygen donors. Up to 780 overall turnovers were obtained in the presence of NaOCl and PhIO, whereas with 30%-H 2O 2 only catalase activity was observed. Contrary to expectations based on previous results [S. Banfi, A. Manfredi, F. Montanari, G. Pozzi, S. Quici, J. Mol. Catal., 113 (1996) 77], only racemic epoxides were obtained.

Ativação do peróxido de hidrogênio para a epoxidação de olefinas não-funcionalizadas Activating agents of the hydrogen peroxide in the epoxidation of unfunctionalized alkenes

A general overview about the more useful activating agents of the hydrogen peroxide in the epoxidation of unfunctionalized alkenes, focusing mechanistic proposals. Moreover, reactivity and stereochemistry, including the stereogenic effect of the hydroxyl group is presented.

A C2 Symmetric Chiral Ketone for Catalytic Asymmetric Epoxidation of Unfunctionalized Olefins

A <i>C</i>₂ Symmetric Chiral Ketone for Catalytic Asymmetric Epoxidation of Unfunctionalized Olefins

Low temperature asymmetric epoxidation of unfunctionalized olefins catalyzed by (salen)Mn(III) complexes

Abstract The enantioselective epoxidation of olefins catalyzed by (salen)Mn(III) complexes can be effected under anhydrous conditions with a variety of primary oxidant systems. The combination of m -CPBA and NMO is particularly reactive, allowing for epoxidation reactions to be carried out at −78 °C. Under these low temperature conditions, a variety of unfunctionalized olefins undergo epoxidation with a significant increase in enantioselectivity relative to reaction using aqueous bleach.