Epoxidation Of Various Olefins Research Articles

Oxidation of alkenes catalysed by molybdenum(VI)–oxodiperoxo complex anchored on the surface of magnetic nanoparticles under solvent‐free conditions

A new epoxidation catalyst has been prepared by grafting a molybdenum(VI)–oxodiperoxo complex containing an oxazine ligand, [MoO(O2)2(phox)], on chloro‐functionalized Fe3O4 nanoparticles. The synthesized heterogeneous catalyst (MoO(O2)2(phox)/Fe3O4 was characterized using powder X‐ray diffraction, scanning and transmission electron microscopies, vibrating sample magnetometry, energy‐dispersive X‐ray analysis, Fourier transform infrared spectroscopy and inductively coupled plasma atomic emission spectroscopy. The immobilized complex gave high product yields and high selectivity for epoxide compared to the corresponding homogeneous one in the epoxidation of various olefins in the presence of tert‐butyl hydroperoxide at 95°C without any co‐solvent. Also, the heterogeneous catalyst can be recycled without a noticeable change in activity and selectivity.

ChemInform Abstract: Enantioselective Epoxidation of Olefins with H2O2 Catalyzed by Bioinspired Aminopyridine Manganese Complexes.

A novel family of bioinspired manganese(II) complexes bearing chiral aminopyridine ligands that possessed additional aromatic groups and strong donating dimethylamino groups were synthesized and characterized. These manganese complexes exhibited efficient and improved activities in the asymmetric epoxidation of various olefins, such as styrene derivatives (up to 93% ee) with H2O2 as the oxidant, even with a catalytic amount of carboxylic acid as the additive.

ChemInform Abstract: One‐Pot Epoxidation of Alkenes Using Aerobic Photoperoxidation of Toluenes.

AbstractEfficient epoxidation of various alkenes is achieved using 4‐tert‐butylperoxybenzoic acid, generated in situ by aerobic photooxidative synthesis.

Mn(TPPS)] immobilized on ionic liquid-modified silica as a heterogeneous and reusable catalyst for epoxidation of alkenes with NaIO4 under ultrasonic irradiation

Effective epoxidation of alkenes using sodium periodate was accomplished with Manganese (III) tetrakis(p-sulfonatophenyl)porphyrin, [C44H26N4O12S4Na4], supported on ionic liquids-modified silica, Im-SiO2, under ultrasonic irradiation conditions is reported. This heterogeneous catalyst, [Mn(TPPS)@SiO2-Im] was characterized by elemental analysis, scanning electron microscopy (SEM), FT-IR and UV–Vis spectroscopic methods. The synthesized hybrid catalyst was applied for efficient epoxidation of various alkenes with sodium periodate in acetonitrile under ultrasonic irradiation conditions. This solid catalyst can be easily recovered by simple filtration and reused several time without apparent loss of its catalytic activity.

Enantioselective Epoxidation of Olefins with H2O2 Catalyzed by Bioinspired Aminopyridine Manganese Complexes.

A novel family of bioinspired manganese(II) complexes bearing chiral aminopyridine ligands that possessed additional aromatic groups and strong donating dimethylamino groups were synthesized and characterized. These manganese complexes exhibited efficient and improved activities in the asymmetric epoxidation of various olefins, such as styrene derivatives (up to 93% ee) with H2O2 as the oxidant, even with a catalytic amount of carboxylic acid as the additive.

Immobilizing of oxo-molybdenum complex on cross-linked copolymer and its catalytic activity for epoxidation reactions

This work describes the immobilization of molybdenum acetylacetonate oxygen (MoO2(acac)2) on cross-linked porous copolymer support via covalent attachment under mild conditions. The obtained solid product DVB–AA–Mo was fully characterized by FT-IR, TG, CHN elemental analysis, nitrogen adsorption/desorption, and SEM, and was tested for the epoxidation of various alkenes with tert-butyl hydroperoxide (TBHP) as the oxidant. DVB–AA–Mo was proved to be a highly efficient catalyst for epoxidation reactions, it could easily be recovered by filtration and reused for five runs without significant loss in activity.

A cobalt(II) complex with anionic and neutral N-donor ligands: synthesis, crystal structure, and application as a heterogeneous catalyst for olefin epoxidation with tert-BuOOH

A cobalt(II) complex containing deprotonated mefenamic acid (Hmef) and imidazole (HIm), [Co(mef)2(HIm)2(CH3OH)2], has been synthesized and characterized by spectroscopic techniques (UV–vis, IR, and EPR), elemental analysis, and single-crystal X-ray diffraction analysis. The structure has distorted octahedral geometry around cobalt. The mefenamate is a monodentate ligand coordinated to the Co(II) through a carboxylate oxygen. This complex was tested as a catalyst for epoxidation of alkenes with tert-BuOOH in 1,2-dichloroethane solution. This catalyst was effective in epoxidation of various alkenes including non-activated terminal alkenes. The effects of solvent, oxidant, and temperature on the epoxidation of cyclohexene were investigated. In all cases, high yields of epoxidized alkenes were obtained.

Electron deficient nonplanar β-octachlorovanadylporphyrin as a highly efficient and selective epoxidation catalyst for olefins.

We have synthesized 2,3,7,8,12,13,17,18-octachloro-meso-tetraphenylporphyrinatooxidovanadium(iv) (VOTPPCl8) and characterized by various spectroscopic (UV-Vis, IR and EPR) techniques, MALDI-TOF mass spectrometry and elemental analysis. The DFT optimized structure of VOTPPCl8 in CH3CN exhibited a highly nonplanar saddle shape conformation of the porphyrin macrocycle. The cyclic voltammogram of VOTPPCl8 showed a 500 mV anodic shift in the first ring reduction potential and 220 mV in the first ring oxidation potential compared to VOTPP indicating the electron deficient nature of the porphyrin π-system and further proving the existence of a nonplanar conformation of the macrocycle in solution. Further, VOTPPCl8 exhibited very high thermal stability till 390 °C as indicated in its thermogram. The oxidation state of the metal ion (V(IV)) was confirmed by EPR spectroscopy and VOTPPCl8 exhibited an axial spectrum which corresponds to the axially compressed dxy(1) configuration. VOTPPCl8 was utilised for the selective epoxidation of various olefins in good yields with very high TOF numbers (6566-9650 h(-1)) in the presence of H2O2 as an oxidant and NaHCO3 as a promoter in a CH3CN/H2O mixture. The oxidoperoxidovanadium(v) species is expected to be the intermediate during the catalytic reaction which is probed by (51)V NMR spectroscopy and MALDI-TOF mass analysis. Notably, VOTPPCl8 is stable after the catalytic reaction and doesn't form a μ-oxo dimer due to the highly electron deficient nonplanar porphyrin core and can be reused for several cycles.

A Mononuclear Manganese Complex of a Tetradentate Nitrogen Ligand – Synthesis, Characterizations, and Application in the Asymmetric Epoxidation of Olefins

AbstractA new chiral manganese complex (C1) bearing a tetradentate nitrogen ligand containing chiral bipyrrolidine and benzimidazole moieties was prepared. The structure of C1 was confirmed by ESI‐MS and crystallography. This manganese complex is an active catalyst for the asymmetric epoxidation of various olefins with excellent conversion (up to 99 %) and high enantiomeric excess (up to 96 % ee) with hydrogen peroxide as the oxidant in the presence of 2‐ethylhexanoic acid or acetic acid. Compared with previous structurally similar manganese complexes with different diamine backbones (C2, cyclohexanediamine; C3, diamine from L‐proline), C1 showed improved asymmetric induction, especially for simple olefins such as styrene derivatives and substituted chromene. The possible reasons for the improvement of the ee values are discussed in the text on the basis of the crystal structures of the manganese complexes.

ChemInform Abstract: Dioxomolybdenum(VI) Complex Covalently Attached to Amino‐Modified Graphene Oxide: Heterogeneous Catalyst for the Epoxidation of Alkenes.

Transition metal salen complex MoO2–salen was successfully tethered onto amino-functionalized graphene oxide (designated as MoO2–salen–GO), which was tested in the epoxidation of various alkenes using tert-butylhydroperoxide or H2O2 as oxidant. Characterization results showed that dioxomolybdenum(VI) complex was successfully grafted onto the amino-functionalized graphene oxide and the structure of the graphene oxide was well preserved after several stepwise synthesis procedures. Catalytic tests showed that heterogeneous catalyst MoO2–salen–GO was more active than its homogeneous analogue MoO2–salen in the epoxidation of cyclooctene due to site isolation. In addition, the MoO2–salen–GO catalyst could be reused three times without significant loss of activity. Copyright © 2014 John Wiley & Sons, Ltd.

Epoxidation of olefins catalyzed by a molybdenum-Schiff base complex anchored in the pores of SBA-15

Novel mesostructured hybrid materials containing a molybdenum Schiff base complex grafted on the internal surface of SBA-15 pores were prepared by introducing MoO2(acac)2 into a mesoporous silica functionalized with Schiff base ligands. The SBA-15 supports modified by an amine or salicylaldehyde were obtained by co-condensation of tetraethylorthosilicate and the corresponding organosilane in the presence of Pluronic P123 surfactant as a structure directing agent using bis[3-(trimethoxysilyl)propyl]amine or 5-chloromethylsalicylaldehyde coupled with bis[3-(trimethoxysilyl)propyl]amine as precursor. The molybdenum (VI) complexes immobilized on the internal surface of SBA-15 pores were employed as catalyst in the epoxidation of various alkenes using tert-butylhydroperoxide as oxidant. These immobilized molybdenum complexes are highly active and selective catalysts in liquid phase olefin epoxidation in dichloroethane at 84°C. Leaching tests and metal analysis of reaction solutions showed that the kinetically competent catalyst is the molybdenum complex immobilized on the internal surface of SBA-15 pores and there is no molybdenum species in the solution.

A New Mesoporous Cobalt Metal-organic Framework was Synthesized by Post-functionalization and Its Application for the Epoxidation of Olefins

A newly Co2+ coordinated metal-organic framework had been successfully synthesized via one-step post-functionalization by hydrothermal method and characterized by Fourier transform infrared spectrometer,N2 adsorption and inductively coupled plasma. Using O2 as oxidant,mesoporous cobalt metal-organic framework was investigated as a heterogeneous catalytic material for the epoxidation of various olefins. Among them,the conversion of cyclooctene and the selectivity of epoxycyclooctane are 94% and 91%,respectively,and the turnover frequency is 509 h- 1. PCN-100( Co) exhibits excellent stabilities in 5 recycles without any loss of catalytic performance.

Mild oxidation of alkenes catalyzed by Fe3O4/SiO2 nanoparticles

In this work, Fe3O4/SiO2 nanoparticles were synthesized according to the literature and characterized by transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis and vibrating sample magnetometer. The catalytic properties of the Fe3O4/SiO2 catalyst have been tested in the epoxidation of different cyclic and acyclic alkenes with m-chloroperbenzoic acid (oxidizing agent). Under optimized conditions, all reactions afforded the desired products in good to excellent yields. Furthermore, the effect of different additives such as pyridine N-oxide and N-methylmorpholine-N-oxide was tested on the conversion of alkenes, but in all cases additives did not improve epoxidation yields. As a result, the Fe3O4/SiO2 showed good activity and super stability in the epoxidation of various olefins. Moreover, this catalyst can be recovered by using a magnetic field and recycled for several times without a significant loss in the catalytic activity.

Dioxomolybdenum(VI) complex covalently attached to amino‐modified graphene oxide: heterogeneous catalyst for the epoxidation of alkenes

Transition metal salen complex MoO2–salen was successfully tethered onto amino‐functionalized graphene oxide (designated as MoO2–salen–GO), which was tested in the epoxidation of various alkenes using tert‐butylhydroperoxide or H2O2 as oxidant. Characterization results showed that dioxomolybdenum(VI) complex was successfully grafted onto the amino‐functionalized graphene oxide and the structure of the graphene oxide was well preserved after several stepwise synthesis procedures. Catalytic tests showed that heterogeneous catalyst MoO2–salen–GO was more active than its homogeneous analogue MoO2–salen in the epoxidation of cyclooctene due to site isolation. In addition, the MoO2–salen–GO catalyst could be reused three times without significant loss of activity. Copyright © 2014 John Wiley & Sons, Ltd.

Polyoxometalate anion-functionalized ionic liquid as a thermoregulated catalyst for the epoxidation of olefins

A new polyoxometalate anion-based functionalized ionic liquid has been synthesized, characterized and employed as catalyst for the epoxidation of various olefins. The ionic liquid catalyst was found to be dissolved considerably in ethyl acetate as the temperature increased during the reaction, but it was recovered conveniently by a thermoregulated-phased separation after the reaction. The thermoregulated catalyst can be efficiently recycled for 17 times without significant changes in the catalytic activity.

Epoxidation of olefins with molecular oxygen as the oxidant using gold catalysts supported on polyoxometalates

We report a highly efficient green process for the epoxidation of various olefins using polyoxometalate-supported gold nanoparticles as catalysts and using oxygen as the terminal oxidant. The nanoparticles were prepared through thermal reduction of Au(III) and were characterised by TEM and XPS. The elemental composition of the catalyst was also determined using ICP. The results show that higher calcination temperatures give a higher degree of reduction, but also result in some sintering of the particles. The catalytic epoxidation reaction may be carried out with or without a solvent and with air or molecular oxygen as the stoichiometric oxidant and using t-butyl hydroperoxide as an initiator. The method shows consistently high conversions and >90% selectivity to epoxide formation for norbornene and cyclooctene oxidation. The catalysts show little deactivation with time and are easily recovered by filtration and can be reused with little or no loss in activity and selectivity.

Co6(μ3-OH)6cluster based coordination polymer as an effective heterogeneous catalyst for aerobic epoxidation of alkenes

A new hexaprismane Co(II)6(μ3-OH)6 cluster-based three-dimensional coordination polymer ({Co(μ3-OH)(HCOO)0.72(CH3COO)0.28}n, Co6-CP) was successfully synthesized and characterized with single-crystal XRD, IR spectra, TGA spectra and elemental analysis. Co6-CP was used as an effective heterogeneous catalyst for the aerobic epoxidation of various alkenes. For the catalytic epoxidation of trans-stilbene, the conversion and selectivity towards the epoxide reached 98.6 and 98.0%, respectively. Also, an average TOF of 22 h(-1) was obtained for the reaction. The results indicated that Co6-CP displayed excellent aerobic epoxidation activity among the reported coordination polymer materials, even rivaling the traditional heterogeneous cobalt catalysts. The influence of the reaction parameters such as temperature and oxygen flow rate for the epoxidation of the trans-stilbene were also studied in detail.

Grafting of a chiral Mn(iii) complex on graphene oxide nanosheets and its catalytic activity for alkene epoxidation

A chiral Mn(III) complex supported by a covalent grafting method on modified graphene oxide was synthesized using 3-chloropropyltrimethoxysilane as a reactive surface modifier. The heterogeneous catalyst was characterized by X-ray diffraction, Fourier transform infrared spectra, thermogravimetric analysis, ultraviolet-visible spectra, nitrogen adsorption–desorption isotherms, transmission electron microscopy and atomic absorption spectroscopy. The catalytic potential of the heterogeneous catalyst and comparison with its homogeneous counterpart were studied for enantioselective epoxidation of various alkenes using m-chloroperbenzoic acid as an oxidant and it showed high selectivity and comparable catalytic reactivity with its homogeneous analogue. In addition, higher enantioselectivity and higher yield were observed in the presence of 4-methylmorpholine N-oxide and pyridine N-oxide, respectively. The catalyst was reused for several runs without significant loss of activity and selectivity.

ChemInform Abstract: Dioxidomolybdenum(VI) Complexes Containing Ligands with the Bipyrrolidine Backbone as Efficient Catalysts for Olefin Epoxidation.

AbstractAir‐stable chiral title Mo(VI)‐complexes of the type MoO2(L) are found to be efficient and selective catalysts for the epoxidation of various olefins.

Cobalt(III) Schiff base complex: Synthesis, X-ray structure and aerobic epoxidation of olefins

A new Co(III) Schiff-base complex, [Co(HL)2]NO3·H2O (1) (H2L=1-(N-3-methoxy-salicylideneimino)-ethane-2-ol), has been synthesized and characterized by several physicochemical methods. X-ray crystal structure analysis revealed that complex 1 features a distorted octahedral coordination geometry and the metal center is surrounded by two tridented N,O,O-donor Schiff base ligands (HL−). [Co(HL)2]NO3·H2O (1) is capable of activating dioxygen in air to catalyze the epoxidation of various alkenes using isobutraldehyde as a co-reductant under homogeneous conditions. It was observed that the yield of the epoxides and their selectivity is highest in acetonitrile medium.