Selective Epoxidation Of Alkenes Research Articles

HClO‐Mediated Photoelectrochemical Epoxidation of Alkenes with Near 100 % Conversion Rate and Selectivity by Regulating Lattice Chlorine Cycle

AbstractDirectional organic transformation via a green, sustainable catalytic reaction has attracted a lot of attention. Herein, we report a photoelectrochemical approach for highly selective epoxidation of alkenes in a salt solution using Co2(OH)3Cl (CoOCl) as a bridge of photo‐generated charge, where the lattice Cl− of CoOCl can be oxidized to generate HClO by the photo‐generated holes of BiVO4 photoanode and be spontaneously recovered by Cl− of a salt solution, which then oxidizes the alkenes into the corresponding epoxides. As a result, a series of water‐soluble alkenes, including 4‐vinylbenzenesulfonic acid sodium, 2‐methyl‐2‐propene‐1‐sulfonic acid sodium, and 3‐methyl‐3‐buten‐1‐ol can be epoxidized with near 100 % conversion rate and selectivity. Through further inserting a MoOx protection layer between BiVO4 and CoOCl, the stability of CoOCl−MoOx/BiVO4 can be maintained for at least 120 hours. This work opens an avenue for solar‐driven organic epoxidation with a possibility of on‐site reaction around the abundant ocean.

HClO-Mediated Photoelectrochemical Epoxidation of Alkenes with Near 100 % Conversion Rate and Selectivity by Regulating Lattice Chlorine Cycle.

Directional organic transformation via a green, sustainable catalytic reaction has attracted a lot of attention. Herein, we report a photoelectrochemical approach for highly selective epoxidation of alkenes in a salt solution using Co2 (OH)3 Cl (CoOCl) as a bridge of photo-generated charge, where the lattice Cl- of CoOCl can be oxidized to generate HClO by the photo-generated holes of BiVO4 photoanode and be spontaneously recovered by Cl- of a salt solution, which then oxidizes the alkenes into the corresponding epoxides. As a result, a series of water-soluble alkenes, including 4-vinylbenzenesulfonic acid sodium, 2-methyl-2-propene-1-sulfonic acid sodium, and 3-methyl-3-buten-1-ol can be epoxidized with near 100 % conversion rate and selectivity. Through further inserting a MoOx protection layer between BiVO4 and CoOCl, the stability of CoOCl-MoOx /BiVO4 can be maintained for at least 120 hours. This work opens an avenue for solar-driven organic epoxidation with a possibility of on-site reaction around the abundant ocean.

Ultra‐low Mn(salen) supported on lignin and selective epoxidation of olefins

AbstractPrecise design of highly efficient, low metal load and eco‐friendly catalysts is the key to sustainable catalysis and green chemistry. In this work, we develop an ultra‐low loading of Mn(salen) complexes covalent grafted with lignin and applied in the selective epoxidation of olefins using O2 as an oxidant. Lignin not only provides the Mn(salen) graft sites but also promotes substrate enrichment via the π‐stacking interaction between substrate and supports. In particular, high turnover frequencies (TOF) of 1833 h−1 can be obtained for styrene epoxidation under mild conditions, which can be superior to most reported Mn(salen) supported catalysts. Compared with cellulose, the lignin‐based catalysts exhibit a higher selectivity toward styrene oxide during the epoxidation of styrene under mild conditions. Controlled experiments indicate that the synergistic effect between phenolic hydroxyl groups and the Mn(salen) complex can improve the conversion rate and selectivity during the selective epoxidation of styrene. This work designs a series of lignin‐based catalysts with ultra‐low Mn(salen) loading, which broadens the utilization of lignin and gives enlightenment for the rational design of lignin‐based catalysts.

Amino-induced cadmium metal–organic framework based on thiazole ligand as a heterogeneous catalyst for the epoxidation of alkenes

Selective epoxidation of olefins is of high interest in the chemical industry due to the many applications of epoxides. This study reports on the synthesis of Cd-MOF, [Cd(DPTTZ)(5-AIP)] (IUST-1) (where DPTTZ = 2, 5-di (pyridine-4-yl) thiazolo [5, 4-d] thiazole, 5-AIP = 5-Aminoisophthalic acid), by a reflux method, which can be considered as a fast and simple process. The morphology and structure of the synthesized IUST-1 were determined by using FE-SEM (Field Emission Scanning Electron Microscopy), EDX (Energy Dispersive Analysis of X-ray), Mapping (Elemental Mapping), CHNS (Elemental analysis), XRD (X-Ray Diffraction), FT-IR (Fourier Transform Infrared), and TGA (Thermo Gravimetric Analysis). The epoxidation of cyclooctene was investigated using the activity of catalytic IUST-1. The results showed that in the presence of tert-butyl hydroperoxide and CCl4 in a 1:2 alkene/oxidant ratio, a high epoxide yield (99.8%) was obtained. In addition, IUST-1 can be easily separated by simple filtration and recycled five times successfully with a slight decrease in activity. This compound has some advantages such as high yield, short reaction time, and ease of reuse, which make it a suitable heterogeneous catalyst for the epoxidation of cyclooctene.

Synthesis and Characterization of New Lutidinium Ionic Liquid-Supported Vanadylsalicylaldoxime Complex for Catalytic Application in Epoxidation Reaction.

A new chelating task-specific ionic liquid (TSIL), lutidinium-based salicylaldoxime (LSOH), and its square pyramidal vanadyl(II) complex (VO(LSO)2 ) have been successfully synthesized and structurally characterized using elemental (CHN), spectral, and thermal analyses. The catalytic activity of the lutidinium-salicylaldoxime complex (VO(LSO)2 ) in the alkene epoxidation reactions was studied under various reaction conditions, such as solvent effect, alkene/oxidant molar ratio, pH, reaction temperature, reaction time, and the catalyst dose. The results demonstrated that the CHCl3 solvent, 1 : 3 of the cyclohexene/H2 O2 ratio, pH 8, temperature of 340 K, and catalyst dose of 0.012 mmol are assigned as the optimum conditions for achieving maximum catalytic activity for VO(LSO)2 . Moreover, the VO(LSO)2 complex has the potential for application in the effective and selective epoxidation of alkenes. Notably, under optimal VO(LSO)2 conditions, cyclic alkenes convert more efficiently to their corresponding epoxides than linear alkenes.

Well-dispersed Mn/g-C3N4 as bifunctional catalysts for selective epoxidation of olefins and carbon dioxide cycloaddition

Epoxidation is an important chemical process for the production of epoxides, key building blocks in chemical industry. Despite great efforts being made to facilitate this process, it remains a significant challenge to develop cost-effective, environmental-friendly, and selective catalysts. Herein, we reported a highly dispersed Mn supported by g-C3N4 (Mn/g-C3N4) with Mn loading up to 2.56 wt%. The Mn/g-C3N4 exhibited satisfied catalytic performance for olefin epoxidation with excellent conversion (91%), high selectivity (93%) as well as outstanding recycling stability. Further analysis revealed the importance of Mn-N structure for the generation of active oxo-containing species and subsequent oxygen atom transfer. Besides, an efficient synthesis of cyclic carbonates from styrene epoxide and CO2 has been achieved (88% conversion, 89% selectivity) based on the polar Mn-N coordinated characteristics of Mn/g-C3N4 catalyst.

Electronically Tuned Copper Porphyrins for the Selective Epoxidation of Alkenes

Electronically Tuned Copper Porphyrins for the Selective Epoxidation of Alkenes

Study on the epoxidation of olefins with H2O2 catalyzed by biquaternary ammonium phosphotungstic acid

Selective epoxidation of olefins is an important field in chemical industry. In this work, we developed a new phosphotungstic acid catalyst {[(C8H17)(CH3)2N]2(CH2)3}1.5{PO4[WO(O2)2]4} with long carbon chain and biquaternary ammonium cation. Cyclohexene could be epoxidized to cyclohexene oxide in 96.3% conversion and 98.2% selectivity. The catalyst type, solvent type, catalyst loading, initial molar ratio, temperature, cycle performance and substrate extensibility were studied and optimized, the kinetic parameters about overall reaction and unit reaction were also calculated. Dynamic light scattering analysis was carried out to explain the different catalytic performance between catalysts with different carbon chain length. This novel catalyst and the corresponding dynamics and mechanism study could probably help the industrial application on the epoxidation of cyclohexene with H2O2.

A continuous protocol for the epoxidation of olefins, monocyclic terpenes, and Alpha Beta Unsaturated Carbonyl Synthons using eco-friendly Flow Reactor Conditions

Herein, we report a simple synthetic protocol for selective epoxidation of olefins, monocyclic terpenes, and chalcones using a continuous semi-batch process in good to excellent yields. Mainly, industrial semi-batch epoxidation is an extremely risky process that includes very high safety measures to avoid the accumulation of peroxide species in the reactor during the process, which leads to accidents. To avoid the same, we have established a constant flow reactor protocol for the epoxidation of fore mentioned key synthons using a cyanamide-potassium carbonate catalytic system which helps to reduce the accumulation of the peroxide species, and also yields moderate to high yields of the desired products. The developed methodology was successfully utilized for the epoxidation of a range of aliphatic to aromatic olefins to generate corresponding epoxides. All the products and their structures were examined using 1HNMR, and 13NMR spectroscopy. More importantly, this proposed protocol is recyclable and reproducible where in using similar research conditions.

Dioxo-molybdenum(VI) unsymmetrical Schiff base complex supported on CoFe2O4@SiO2 nanoparticles as a new magnetically recoverable nanocatalyst for selective epoxidation of alkenes

Dioxo-molybdenum(VI) unsymmetrical Schiff base complex supported on CoFe2O4@SiO2 nanoparticles as a new magnetically recoverable nanocatalyst for selective epoxidation of alkenes

Selective epoxidation of olefins by vanadylporphyrin [VIVO(TPP)] and electron deficient nonplanar β-octabromovanadylporphyrin [VIVO(TPPBr8)

Meso-tetraphenylporphyrinatooxidovanadium(IV) [VIVO(TPP)] (1) and 2,3,7,8,12,13, 17,18-octabromo-meso-tetraphenylporphyrinatooxidovanadium(IV) [VIVO(TPPBr[Formula: see text]] (2) were synthesized and characterized by various spectroscopic techniques. 1 and 2 were utilized as efficient catalysts for the selective epoxidation of olefins. Catalyst 2 shows very high catalytic activity (TOF = 8783–13108 h[Formula: see text] as compared to 1 (TOF = 2175–3296 h[Formula: see text]. The catalysts are recyclable, as their recyclability was checked for four cycles and show only minor reduction of their efficiency.

Ag nanoparticles immobilized over highly porous crystalline organosilica for epoxidation of styrene using CO2 as oxidant

Selective epoxidation of olefins is a very important reaction as epoxides are widely been used as platform chemical in polymer and pharmaceutical industries. Unlike conventional oxidants like molecular O2 or peroxides, the use of CO2 as a soft oxidant for the oxidation of olefins is very challenging as it offers the utilization of waste and plentiful CO2 together with the potential for the mitigation of its harmful environmental effect. Thus, this process is cost effective and environmentally challenging. Herein, we report the synthesis of a new crystalline porous organosilica material TSOS-1 with orthorhombic crystal structure by using a tailor made bridging organoslilane precursor prepared through the Schiff base condensation of p-terphenyl-4,4′'-dialdehyde and 3-aminopropyl-trimethoxysilane. This novel crystalline material TSOS-1 has been synthesized hydrothermally in the absence of any structure-directing agent and it showed high BET surface area (220 m2 g−1) and nanoscale porosity. TSOS-1 is used as a support for stabilizing tiny AgNPs to obtain a robust nanocatalyst Ag@TSOS-1, which efficiently catalyses the conversion of styrene into predominantly styrene oxide (SO) using CO2 as a soft oxidant in an autoclave reactor under mild reaction conditions.

Co(II) Schiff base Complexes Encapsulated in the Nanopores of Zeolite Y as Heterogeneous Catalysts for Selective Epoxidation of Alkenes with Molecular Oxygen

Co(II) Schiff base Complexes Encapsulated in the Nanopores of Zeolite Y as Heterogeneous Catalysts for Selective Epoxidation of Alkenes with Molecular Oxygen

Substitution of Cetyltrimethylammonium for OSDA Cations During B-SSZ-70 Zeotype Synthesis and Its Influence on Delamination

We investigated the substitution of structure-directing agent diisobutylimidazolium hydroxide with cetyltrimethylammonium hydroxide (CTA+OH−) surfactant in the synthesis gel of layered-zeotype-precursor B-SSZ-70(P). At low substitution levels, CTA+ interacts with the external-zeotype surface, where it assembles. At higher surfactant amounts, CTA+ intercalation occurs, leading to swelling of the precursor material, as evidenced by powder X-ray diffraction. Characterization of adsorbed CTA+ cations by 13C MAS NMR spectroscopy demonstrates unique broad resonances in the intercalated layers, which represent a more rigid environment than in the external-surface assemblies. At still higher CTA+ substitution levels in the synthesis gel, we observe the formation of amorphous mesoporous silica. We attempted to delaminate materials synthesized with varying CTA+ substitution levels using mild conditions, in which the conventional sonication step is replaced with an easy-to-scale high-shear mixing, and in which the use of halide reagents, which are corrosive and have been required in the past, is also avoided. Our data demonstrate that synthesis of a swollen material per se is not essential as an intermediate for delamination, and that layered zeolite precursor swelling can actually undermine zeolite delamination. Our results instead point to the CTA+ external-surface assemblies as facilitating ease of SSZ-70 delamination under these mild conditions. When calcined and functionalized with grafted titanium centers, the delaminated materials are highly active and selective olefin epoxidation catalysts with organic hydroperoxides, showing a 40% higher epoxide conversion than a catalyst prepared from conventional B-SSZ-70.

Olefin epoxidation with ionic liquid catalysts formed by supramolecular interactions

This work demonstrated that the specific ionic liquids (ILs) have been designed via the supramolecular complexation between 18-crown-6 (CE) and ammonium peroxoniobate (NH4-Nb). The resultant ILs have been characterized by elemental analysis, FT-IR, Raman, NMR, DSC, conductivity measurement and MALDI-TOF, etc. The IL (CE-1) consisting of CE and ammonium peroxoniobate can be further coordinated with GLY to generate a new IL (CE-2), which showed both high catalytic activity in epoxidation with H2O2 and good recyclability. The characterization of 93Nb NMR spectra revealed that the peroxoniobate anions has demonstrated a structural evolution in the presence of hydrogen peroxide, in which NbO species can be easily oxidized into the catalytically active niobium−peroxo species. Especially, the supramolecular complexation can provide suitable hydrophobicity, which ensured that the hydrophobic olefins and allylic alcohols were easily accessible to the catalytically active anions, and thus facilitated the epoxidation reaction. Notably, the supramolecular IL catalysts in this work exhibited a huge advantage of the easy availability, as compared with the previously reported peroxoniobate-based ILs. As far as we know, this is the first example of the highly selective epoxidation of olefins and allylic alcohols by using supramolecular ILs as catalysts.

Copper complex supported on hollow porous nanosphere frameworks with improved catalytic activity for epoxidation of olefins

Abstract An efficient heterogeneous catalyst has been synthesized by anchoring copper complex onto the salicylaldehyde-modified hollow porous nanosphere frameworks (SA-HPNFs-BA), in which SA-HPNFs were firstly prepared by using amino-functionalized HPNFs to react with salicylaldehyde. The final copper complex functionalized hollow porous nanosphere frameworks (Cu-HPNFs-BA) possess the high specific surface area, hierarchically micro-/mesoporous structure and robust organic frameworks. The prepared Cu-HPNFs-BA heterogeneous catalyst shows improved catalytic performance and good recycling stability in selective epoxidation of olefins.

Tungstenocene-grafted silica catalysts for the selective epoxidation of alkenes

Tungstenocene(IV) dichloride was successfully deposited and grafted on the surface of a commercially-available non-ordered silica support via either a liquid-phase or a dry impregnation approach. After a high-temperature calcination step, two W(VI)-grafted silica catalysts, with a metal loading around 1.2–1.7 wt.%, were obtained. They were fully characterized by physisorption and spectroscopic techniques, which evidenced well-dispersed tungsten oxide polyoxo cluster sites, for the catalyst prepared via liquid-phase grafting, and evenly dispersed larger monoclinic tungsten(VI) oxide aggregates, for the catalyst prepared via dry impregnation, respectively. Both W/SiO2 solids showed moderate to good conversion values in the epoxidation of (R)-(+)-limonene and methyl oleate (up to 68%), in the presence of aqueous hydrogen peroxide, with good selectivity to the desired epoxides (63% and 78%, respectively). The heterogeneous character of the most interesting W/SiO2 catalyst prepared via dry impregnation was confirmed by a hot centrifugation test and by an extended recovery and reuse of the solid in six catalytic runs.

Vanadyl β-tetrabromoporphyrin: synthesis, crystal structure and its use as an efficient and selective catalyst for olefin epoxidation in aqueous medium.

We hereby report the synthesis, characterization and catalytic applications in the epoxidation of alkenes by a vanadyl porphyrin having bulky bromo substituents at the β-positions viz. vanandyltetrabromotetraphenylporphyrin (1). The synthesized porphyrin was characterized by various spectroscopic techniques like UV-visible, FT-IR, EPR, MALDI-TOF mass spectrometry and single crystal X-ray analysis. Porphyrin 1 has a nonplanar structure as indicated by its X-ray structure, DFT and electrochemical studies. 1 was analyzed for its catalytic application in the epoxidation of various alkenes. The catalytic reactions were carried out in CH3CN/H2O mixture in 3 : 1 (v/v) ratio. 1 displayed good efficiency in terms of mild reaction conditions, lower reaction temperature and minimal catalyst amount consumption. 1 exhibited excellent selectivity, high conversion efficiency and huge TOF (7600–9800 h−1) in a significantly low reaction time of 0.5 h. Catalyst 1 was regenerated at the end of various catalytic cycles making it reusable and industrially important.

Trinuclear Dioxidomolybdenum(VI) Complexes of Tritopic Phloroglucinol‐Based Ligands and Their Catalytic Applications for the Selective Epoxidation of Olefins

Four trinuclear dioxidomolybdenum(VI) complexes, [{MoVIO2(H2O)}3ptk(bhz)3] (1), [{MoVIO2(H2O)}3ptk(fah)3] (2), [{MoVIO2(H2O)}3ptk(inh)3] (3), and [{MoVIO2(H2O)}3ptk(nah)3] (4), based on the tritopic central 2,4,6‐triacetylphloroglucinol (H3ptk) ligands H6ptk(bhz)3 (I), H6ptk(fah)3 (II), H6ptk(inh)3 (III) and H6ptk(nah)3 (IV) (Hbhz = benzoylhydrazide, Hfah = 2‐furanoylhydrazide, Hinh = isonicotinoylhydrazide and Hnah = nicotinoylhydrazide), respectively, are presented. All of the synthesized ligands, as well as their complexes, have been characterized by elemental, thermal, and electrochemical analyses, spectroscopic techniques (FTIR, UV/Vis, 1H and 13C NMR), and single‐crystal X‐ray studies of [{MoVIO2(H2O)}{MoVIO2(MeOH)}2ptk(bhz)3]·2H2O·1.25MeOH (1a) and [{MoVIO2(EtOH)}3ptk(fah)3]·3EtOH (2a). Each pocket of the ligands coordinates in a dibasic tridentate fashion through two oxygen atoms and one nitrogen atom to each metal center. Due to the presence of tridentate binding pockets in the ligands, each metal center conserves its octahedral structure by coordinating with water molecules in the synthesized complexes or by other solvent(s) in the crystal structures. These complexes were evaluated for the epoxidation of terminal and internal alkenes in the presence of H2O2 using NaHCO3 as a promoter. Under the optimized reaction conditions, all alkenes were converted to the corresponding epoxides selectively in good yield and high turnover number.

Covalent functionalization of graphene oxide with molybdenum-carboxylate complexes: New reusable catalysts for the epoxidation of olefins

New graphene oxide (GO) and reduced graphene oxide (rGO) supported molybdenum catalysts were designed for the epoxidation of olefins. First, the surfaces of GO and rGO were functionalized with appropriate carboxylic acid ligands. Complexation of the supported carboxylic acid ligands with bis(acetylacetonato)dioxomolybdenum(VI) resulted in the formation of desired heterogeneous molybdenum catalysts. Characterization of the prepared catalysts was performed with various techniques such as Fourier transform infrared (FT-IR) and inductively coupled plasma optical emission (ICP-OES) spectroscopies, X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), and N2 adsorption-desorption analysis which confirmed the successful immobilization of molybdenum-carboxylate complexes on the surfaces of GO and rGO. The obtained catalysts showed high catalytic activities in the selective epoxidation of olefins with tert-butylhydroperoxide (TBHP). Also, the heterogeneous catalysts were recycled without remarkable decrease in catalytic efficiencies under five successive runs.