Asymmetric Epoxidation Of Unfunctionalized Olefins Research Articles

Asymmetric Epoxidation of Unfunctionalized Olefins Catalyzed by Chiral (Pyrrolidine Salen) Mn (III) Complexes with Proline Sidearms

Four (R, R)-3, 4-diaminopyrrolidine-based chiral Salen ligands with L-Boc-N-proline, D-Boc-N-proline, L-proline, D-proline as respective sidearms, as well as their manganese complexes were synthesized and characterized. These Salen-Mn(III) complexes were applied to the asymmetric epoxidations of unfunctionalized olefins with NaClO, and m-CPBA as respective oxidants. The catalysis of the Salen-Mn (III) complexes varied with the change of sidearms. The one with D-Boc-N-proline as a sidearm showed the best asymmetric catalysis among the four chiral manganese complexes, and its catalysis was also better than that of the one with a benzyl sidearm, and comparable with that of Jacobsen's catalyst. Moderate to excellent enantioselectivities and yields were achieved in the asymmetric of various olefins over this complex. The big enhancement of the D-Boc-N-proline sidearm on the enantioselectivity of the asymmetric epoxidation might be ascribed to its large steric hindrance and appropriate configuration, allowing the Boc moiety to be away from the side-on approach pathway of olefins to the active center but near the opposite side one in some degree, thus facilitating the approach of olefins to the active center from one direction.

Asymmetric Epoxidation of Unfunctionalized Olefins Using Novel Chiral Dihydroisoquinolinium Salts as Organocatalysts

Asymmetric Epoxidation of Unfunctionalized Olefins Using Novel Chiral Dihydroisoquinolinium Salts as Organocatalysts

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.

Oligomeric (Salen)Mn(III) Complexes Featuring Tartrate Linkers Immobilized over Layered Double Hydroxide for Catalytically Asymmetric Epoxidation of Unfunctionalized Olefins.

A series of oligomeric (salen)Mn(III) complexes featuring tartrate linkers were prepared and immobilized over layered double hydroxide, and then used as catalysts for asymmetric epoxidation of unfunctionalized olefins. Comprehensive characterizations including 1H NMR, FT-IR, UV-Vis, elemental analysis, GPC, and ICP-AES were used to illustrate structures of oligomeric (salen)Mn(III) complexes, while powdered XRD, nitrogen physisorption, together with XPS studies provided further details to detect structures of heterogeneous catalysts. Interestingly, scanning electron microscopy found an interesting morphology change during modification of layered supporting material. Catalytic experiments indicated that configuration of major epoxide products was determined by salen chirality more than that of tartrate linker, but enantioselectivity (e.e. values) could be enhanced when tartrate and salen showed identical chiral configurations. Furthermore, the (R,R)-salen moieties linked with (R,R)-tartrate spacers usually offered higher enantioselectivity compared to other combinations. Lastly, Zn(II)/Al(III) layered double hydroxide played as a rigid supporting material in catalysis, showing positive chiral induction and high recycling potential in catalytic reactions.

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.

Chiral salen Mn (III) immobilized on ZnPS-PVPA through alkoxyl-triazole for superior performance catalyst in asymmetric epoxidation of unfunctionalized olefins

Chiral salen Mn (III) catalysts anchored onto ZnPS-PVPA via click chemistry are prepared and applied in asymmetric epoxidations of unfunctionalized olefins. Superior catalytic performances (conv%, up to >99; ee%, up to >99) are achieved in the epoxidations of α-methylstyrene, styrene, indene and 1-octene. According to 6-cyano-2,2-dimethylchromene and 6-nitro-2,2-dimethylchromene, configuration of epoxides are reversed. And then the catalysts are selective in not only oxidative systems, but also substrates. Moreover, superior reusability (yield, 82%; ee, 86%) after recycling for nine times could also be obtained, which provide the potential application in industry.

Asymmetric epoxidation of unfunctionalized olefins with C2-symmetrical diphenol-derived axially coordinated homogeneous chiral bi-Mn(III) salen complexes

A novel type of C2-symmetrical diphenol-derived and axially coordinated homogeneous chiral bi-Mn(III) salen complexes are synthesized and their catalytic effects in asymmetric epoxidation of unfunctionalized olefins are investigated in details. The results show that excellent enantioselectivities and high activities are achieved (enantioselectivities up to >99% in <10 min, and conversions up to >99.9%) in the absence of expensive NMO. Compared with Jacobsen's catalyst, the configuration of C2-symmetrical homogeneous chiral bi-Mn(III) salen complex contribute to the catalytic reactivity and stability. Furthermore, these new homogeneous catalysts could be easily recovered and reused for 5 cycles without significant loss of their properties.

Chiral salen Cr(iii) complexes encapsulated in thermo-responsive polymer nanoreactors for asymmetric epoxidation of alkenes in water

Thermo-responsive polymer nanoreactors containing chiral salen Cr(iii) complexes exhibited unprecedented efficiency and facile reusability in asymmetric epoxidation of unfunctionalized olefins in water.

Heterogeneous Jacobsen's catalyst on alkoxyl‐modified zirconium poly (styrene‐phenylvinylphosphonate)‐phosphate (ZPS‐PVPA) for asymmetric epoxidation

Chiral Jacobsen's catalysts grafted onto alkoxyl‐modified ZPS‐PVPA exhibit excellent activities (conv%, up to 96; sele%, up to 96; ee%, up to &gt;99) in the asymmetric epoxidations of unfunctionalized olefins. The superior stabilities and the comfortable dispositions in large‐scale reactions contribute to the potential applications in industry.

Asymmetric epoxidation of unfunctionalized olefins catalyzed by Jacobsen’s catalyst on alkoxyl-modified zirconium poly (styrene-phenylvinylphosphonate)-phosphate (ZPS-PVPA)

New chiral Jacobsen’s catalysts grafted onto alkoxyl-modified ZPS-PVPA are synthesized and applied in asymmetric epoxidations of unfunctionalized olefins. Specially, the supported catalysts indicate excellent catalytic activities (conv%, up to 96; sele%, up to 96; ee%, up to >99) in the absence of N-methylmorpholine N-oxide (NMO) by virtue of the special configurations of the catalysts. The superior stability (recycling for ten times) and the comfortable dispositions in large-scale reactions (such as 200 times) grant the potential application in industry to the heterogeneous catalysts.

Layered crystalline chiral salen Mn(III) complexes immobilized on organic polymer–inorganic hybrid zinc phosphonate-phosphate as efficient and reusable catalysts for the unfunctionalized olefin epoxidation

Chiral Mn(III) salen complexes grafted on ZnPS-PVPA (zinc poly(styrene-phenylvinyl-phosphonate)-phosphate) upon alkyldiamines through a facile method are evaluated by the asymmetric epoxidation of unfunctionalized olefins. Superior catalytic performances are obtained (conv%, up to >99; ee%, up to >99) whenever with m-CPBA or NaClO or NaIO4 as the oxidant. The additives such as NMO, PPNO as well as imidazole play different roles in the corresponding oxidation system. In addition, the supported catalysts could be reused nine times with the retention of their efficiency. These results highlight the potentiality of ZnPS-PVPA as the support for immobilizing chiral salen Mn(III) to be employed in oxidation reactions.

Asymmetric epoxidation of unfunctionalized olefins accelerated by thermoresponsive self-assemblies in aqueous systems

A thermoresponsive self-assembled nanoreactor, comprising a hydrophilic PNIPAAm shell and a hydrophobic chiral salen MnIII complex core, exhibits unprecedented efficiency and facile reusability in asymmetric epoxidation of unfunctionalized olefins in pure water without using any organic solvents.

Constraining asymmetric organometallic catalysts within mesoporous supports ZnPS–BrPPAS boosts their enantioselectivity

Novel layered heterogeneous chiral salen Mn(III) catalysts are synthesized with organic–inorganic hybrid material ZnPS–BrPPAS as the support and employed in the asymmetric epoxidations of unfunctionalized olefins. Characterizations indicate that the different linkers could contribute to the morphology varying from schistose structure to spheric particle. The catalysts manifest superior catalytic dispositions (yield, up to >99%; ee, up to >99%) in the epoxidations of olefins such as α-methylstyrene and indene. Moreover, the catalysts could be recovered and reused up to nine times with retention of catalytic dispositions. In addition, the reversal configurations of epoxides are observed with respect to 6-cyano-2,2-dimethylchromene and 6-nitro-2,2-dimethylchromene.

Immobilization of Chiral (salen)Manganese(III) Complexes Into Mesoporous Helical Silica for Asymmetric Epoxidation of Alkenes

Chiral (salen)Mn(III) complexes were immobilized into mesoporous helical silica for asymmetric epoxidation of unfunctionalized alkenes, and chiral synergistic effects between supporting material and (salen)Mn(III) were investigated. Characterization revealed both carriers and supported catalysts had a hierarchical structure composed of morphology and internal channels. Supporting materials had helical morphology and excessive left-handed channels, while most supported catalysts still had excessive left-handed channels although their morphology might degrade. Catalysis revealed the synergistic effects between mesoscopic and molecular chirality exist, and the combination of left-handed channels with (R,R)-(salen)Mn(III) appeared to be more enantioselective than that with (S,S)-salen counterpart in epoxidation of terminal and cyclic alkenes.

Ionic liquid-functionalized graphene oxide as an efficient support for the chiral salen Mn(iii) complex in asymmetric epoxidation of unfunctionalized olefins

Chiral salen Mn(iii) complex covalently grafted on IL-functionalized GO sheet, was a highly efficient, universal and reusable catalyst for asymmetric epoxidation of unfunctionalized olefins using aqueous NaOCl as an oxidant.

Reusable chiral salen Mn(III) complexes with phase transfer capability efficiently catalyze the asymmetric epoxidation of unfunctionalized olefins with NaClO

A series of chiral salen Mn(III) polymers with build-in phase transfer capability was prepared by bridging the chiral salen Mn(III) units with polyethylene glycol (PEG)-based di-imidazolium ionic liquid (IL) side by side. Technologies of characterization suggested the alternation of intact chiral salen Mn(III) unit with PEG-based dicationic imidazolium IL moiety in the rigid one-dimension polymers. Amphipathic nature of PEG-based di-imidazolium IL moiety allowed the obtained catalysts to undergo inherent phase transfer catalysis in asymmetric epoxidation of unfunctionalized olefins with NaClO, which in turn increased the reaction rate of epoxidation in water–dichloromethane biphasic system. Decreasing total length of polyether chain leads to an increase in built-in phase transfer capability of corresponding complex, which further enhances the catalytic performance. 91–97% of conversion was obtained in the enantioselective epoxidation of styrene, α-methylstyrene, indene, 1,2-dihydronaphthalene, 6-cyano-2,2-dimethylchromene, and 6-nitro-2,2-dimethylchromene catalyzed by the complex where number of ethylene oxide unit is 3 within 60min, which is significant higher than that observed for the neat complex (56–74%) and the ICP (62–85%). High enantiomeric excess (ee) for the epoxides (in the range of 67–93%) was also achieved, except for styrene (ee, 34%) and α-methylstyrene (ee, 41%). Furthermore, the efficient phase transfer catalysts could be easily recovered by solvent precipitation and be recycled for seven times without significant loss of the activity and enantioselectivity.

Mesoporous material AlPS-BrPPAS derivatives supported chiral Mn(III) salen complex and highly efficient epoxidation of olefins as a recoverable catalyst

A novel layered crystalline of organic–inorganic hybrid material aluminium 3-bromopropylphosphonate-phosphate (AlPS-BrPPAS) was synthesized and used as catalyst supports for immobilization of chiral salen Mn(III) with different types of diamine linkers. The heterogeneous salen Mn(III) catalysts were characterized by FT-IR, XRD, TG, SEM, and N2 sorption, and the results indicated the successful immobilization of the chiral Mn(III) salen complex. It was found that the structure of the catalysts was closely correlated with the linkers. The confinement effect of linkers on the catalytic performance of the heterogeneous catalysts was studied for the asymmetric epoxidation of unfunctionalized olefins with sodium hypochlorite as an oxidant. Moreover, the heterogeneous chiral salen Mn(III) catalysts can be recovered and reused up to nine times with retention of conversion and enantioselectivity. Interestingly, two heterogeneous chiral salen Mn(III) catalysts with different linkers also significantly alter the configuration of epoxide products for 6-cyano-2,2-dimethylchromene and 6-nitro-2,2-dimethyl-chromene.

Immobilized chiral Mn (III) salen-containing onium salt onto ZnPS-PVPA for asymmetric epoxidation of unfunctionalized olefins

A series of chiral Mn (III) salen are anchored on ZnPS-PVPA modified by onium salt and characterized. In the asymmetric epoxidation of unfunctionalized olefins with m-CPBA and NaIO4 as oxidants, the supported catalysts demonstrate higher catalytic activities than those of the corresponding homogeneous chiral Mn (III) salen catalyst under the same conditions both for experimental scale and for large-scale reactions. Moreover, the catalysts are stable could be recycled nine times without significant loss of activity, which are provided with the potentiality for application in industry.

ChemInform Abstract: A Homogeneous Chiral Manganese(III)—Salphe Catalyst for Enantioselective Epoxidation of Olefins.

AbstractA new chiral Mn(III)‐catalyst is synthesized from natural amino acid (R)‐phenylalanine and successfully applied to asymmetric epoxidation of unfunctionalized olefins in an ionic liquid.