Epoxidation Of Cyclopentene Research Articles

Gold Catalyzed [3+2] Oxidative Annulation of 1,3‐Enynes with Indoles

AbstractAn efficient new method has been developed for the synthesis of ketone‐integrated cyclopentene‐fused indoline derivatives with a high regioselectivity through gold‐catalyzed oxidative cyclo‐coupling of 1,3‐enynes with indoles by using 2,6‐dichloropyridine N‐oxide as the terminal oxidant. A plausible mechanism has been proposed, in which, a cascade process of nucleophilic trapping of the vinyl gold carbene surrogate with indole followed by the subsequent intramolecular cyclization provides the dearomative formal [3+2] cycloaddition product. In addition, a scale‐up reaction and further derivation via cyclopentene's epoxidation & hydrazone derivative's 1,5‐ electrocyclization have been performed.

Hydrothermal Modification of TS-1 Zeolites with Organic Amines and Salts to Construct Highly Selective Catalysts for Cyclopentene Epoxidation

Developing efficient heterogeneous catalysts for cyclic olefins epoxidation is highly attractive for meeting the growing need for various cyclic epoxides. Herein, hierarchical TS-1 zeolite with relatively abundant mesopores and less amount of surface hydroxyl groups was obtained by hydrothermal modification of an as-synthesized TS-1 zeolite with a mixed solution of ammonia, tetrapropylammonium bromide (TPABr) and KCl. The post-modified TS-1 zeolite exhibited much higher catalytic activity (52% conversion) and epoxide selectivity (98%) for the epoxidation of cyclopentene than the conventional TS-1 zeolites. The excellent catalytic activity of the hierarchical TS-1 could be mainly assigned to the enhancement of the mass transport ability and the accessibility of the active Ti species, while the improvement of epoxidation selectivity may be mainly related to the introduction of a certain amount of K+ that can effectively modulate the coordination environment of Ti species as well as the polarity of the zeolite. This work demonstrated that a highly active and selective catalyst for the H2O2-mediated cyclopentene epoxidation could be obtained by concurrently generating mesopore and extinguishing the unfavorable defective hydroxyl groups through the simple hydrothermal treatment of the conventional TS-1 zeolite with a mixed base/salt solution.

Oxidation of Cyclopentene with Manganese Oxides Octahedral Molecular Sieves with Layer and Tunnel Structures

AbstractManganese oxides type octahedral molecular sieves OL‐1, OMS‐1, and OMS‐2 were synthesized, impregnated with sodium tungstate, and evaluated as catalysts for the selective epoxidation of cyclopentene (CPE) to cyclopentene oxide (CPO) in the sodium bicarbonate/hydrogen peroxide (BAP) system. OL‐1 was the best catalyst with a conversion of 78.6 % and a selectivity to CPO of 31.4 %. Impregnation with sodium tungstate affected the structure and activity of OL‐1 and OMS‐1. Mn2+ is required for the epoxidation of CPE. FTIR spectra provides evidence that tungstate ions react, during impregnation, with Mg2+ and/or Mn2+ present in OMS‐1 and OL‐1 producing an amorphous compound that is not active in the epoxidation reaction. The crystalline and chemical structure of OMS‐2 was not affected by tungstate impregnation, since most of the manganese occurs as Mn3+ and Mn4+, which in presence of hydrogen peroxide, tend to form radicals, active in the total oxidation of organic compounds.

Assembly of SBA‐15 Derived Hybrid Heterogeneous Catalysts for Liquid Phase Cyclopentene Epoxidation

AbstractThree two‐dimensional SBA‐15‐based hybrid materials, SBA‐15‐ImCl‐PF6, SBA‐15‐NH(PO3H2), and SBA‐15‐N+, were synthesized employing a post‐synthetic functionalization strategy, and peroxo‐W and PW species were successfully immobilized on the surface of the corresponding organic moieties‐modified SBA‐15 via electrostatic interaction or covalent linking. The TEM and XRD results presented that the structure and morphology of SBA‐15 were maintained after multiple transformations. The final catalysts SBA‐15‐ImCl‐PF6‐W, SBA‐15‐NH(PO3H2)‐W, and SBA‐15‐N+(PW4O24)3− all showed considerable activity for the epoxidation of cyclopentene to cyclopentene oxide using H2O2 as the oxygen source without any co‐solvent. It was noteworthy that SBA‐15‐ImCl‐PF6‐W catalyst with increased hydrophobicity via altering counteranions of imisazolium ions exhibited excellent cyclopentene oxide selectivity (99 %), but a good cycle performance (10 times) was achieved via SBA‐15‐NH(PO3H2)‐W owing robust covalent bonds. Besides, the use of a low dose of heterogeneous catalyst (W=20 μmol) and a green oxidant of H2O2, along with the absence of co‐solvent or other additives make cyclopentene epoxidation reaction an environmenttally benign chemical process.

Modified Ti-MWW Zeolite as a Highly Efficient Catalyst for the Cyclopentene Epoxidation Reaction.

The liquid-phase epoxidation of cyclopentene (CPE) was performed in the Ti-zeolite/H2O2 catalytic system for the clean synthesis of cyclopentene oxide. Among all the Ti-zeolites (Ti-Beta, Ti-MOR, Ti-MCM-68, TS-1, TS-2, and Ti-MWW) investigated in the present study, Ti-MWW provided relatively lower CPE conversion of 13% due to the diffusion constrains but a higher CPO selectivity of 99.5%. The catalytic performance of Ti-MWW was significantly enhanced by piperidine (PI) treatment, with the CPE conversion and CPO selectivity increased to 97.8 and 99.9%, respectively. The structural rearrangement upon PI treatment converted the 3-dimensional (3D) MWW structure to a 2D lamellar one, which enlarged the interlayer space and greatly alleviated the diffusion constrains of cyclic cyclopentene. Furthermore, the newly constructed “open site” six-coordinated Ti active sites with PI as the ligand exhibited higher catalytic activity. The two factors contributed to more significant enhancement of the activity upon PI-assisted structural arrangement compared to the cases in linear alkenes.

Epoxidation of cyclopentene by a low cost and environmentally friendly bicarbonate/peroxide/manganese system

The system hydrogen peroxide/sodium bicarbonate/manganese sulfate was used for the first time to epoxidize cyclopentene. Effects of parameters such as type and amount of solvent, ratio of hydrogen peroxide and manganese sulfate to cyclopentene, presence of additives, and reaction time and temperature on the selectivity to cyclopentene oxide were evaluated. Gas chromatography was used to quantify residual cyclopentene and produced cyclopentene oxide using the internal standard method. Type and amount of solvent, addition method, and temperature were important factors to increase the selectivity to cyclopentene oxide. Unlike previous reports on epoxidation of different substrates, additives like sodium acetate and salicylic acid did not improve the selectivity to cyclopentene oxide. One time, single-step addition of hydrogen peroxide/sodium bicarbonate to the solution of cyclopentene/solvent/manganese sulfate produced more cyclopentene oxide than stepwise addition. The maximum selectivity obtained was 56%, possibly due to the high reactivity of cyclopentene that causes the formation of oxidation products different to cyclopentene oxide, which were not detected in the analyzed phase.

Highly Efficient Epoxidation of Cyclopentene Catalyzed by Magnetically Recoverable Mg-doped Cobalt Ferrites with Greatly Improved Performances

The alkaline earth metal Mg-doped CoFe2O4 composite ferrite samples MgxCo1-xFe2O4 (x=0, 0.1, 0.3, 0.5, 0.7 and 1) were prepared using a sol-gel auto-combustion route. The as-prepared samples were characterized by Raman spectrometry, X-ray diffractometry (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), ICP–atomic emission spectroscopy and N2-physisorption. The catalytic activities of the samples were tested in the cyclopentene oxidation using hydrogen peroxide (30 %) as the oxidant. Compared with the pristine CoFe2O4 and MgFe2O4, the Mg−Co composite ferrites showed much enhanced catalytic performances in the oxidation of cyclopentene with cyclopentene oxide as the main product. In particular, 95.2 % of cyclopentene conversion and 96.3 % of selectivity for cyclopentene oxide were achieved when Mg0.5Co0.5Fe2O4 was used at 60 oC for 8 h in the oxidation reaction. The catalyst can be easily separated by applying magnetic field and exhibits great reusability.

The kinetics of the reaction between cyclopentene and aqueous hydrogen peroxide under phase-transfer catalysis

The kinetics of the reaction between cyclopentene and an aqueous solution of hydrogen peroxide under phase-transfer catalysis conditions has been studied. The activation energies of the successive stages of cyclopentene epoxidation to 1,2-epoxycyclopentane and the hydration of the resulting epoxide to 1,2-cyclopentanediol have been found, and the orders of the reactions with respect to the reactants have been determined. A mathematical model of the process that adequately describes the available experimental data in the entire range of reactant concentrations has been proposed.

Efficiency of phase-transfer catalysis in cyclopentene epoxidation with hydrogen peroxide

The effect of the structure and amount of the phase-transfer catalyst (quaternary ammonium salts) and the solvent effect on cyclopentene oxidation with an aqueous hydrogen peroxide solution in the liquid-liquid two-phase system was studied. The phase-transfer catalyst and solvent ensuring high reaction rate and high selectivity with respect to target products were chosen.

Spectroscopic investigation into the nature of the active sites for epoxidation reactions using vanadium-based aluminophosphate catalysts

VAlPO-5 and VAlPO-11 catalysts were synthesized and their structural features characterized by a range of spectroscopic techniques (UV–Vis, Raman and IR spectroscopies) revealing valuable information on the nature of the incorporated vanadium species. A preliminary investigation into the catalytic potential of these catalysts was carried out by studying the epoxidation of cyclopentene to its corresponding epoxide using a solid source of “active” oxygen, acetylperoxyborate (APB) as the oxidant. UV–Vis spectra showed strong bands in the 40,000–35,000 cm −1 range, that can be assigned to isolated Td-like oxovanadium(V) (V 5+ = O vanadyls), along with a component around 35,000 cm −1 due to a small fraction of Td V 5+ = O in di- or oligomeric V xO y clusters. The V 5+ = O ions were reversibly transformed to V 4+ = O species by reduction, and could also change their coordination (to octahedral geometry) in the presence of water molecules. The presence of isolated V 5+ = O was confirmed by resonant Raman studies. IR spectroscopy of adsorbed probes (CO and NO) revealed the presence of two families of framework V 4+ = O ions with different Lewis acidity V A 4 + and V B 4 + forming monocarbonyls (bands at 2192 cm −1 and 2184 cm −1) and di-nitrosyls (bands at 1905–1755 cm −1 and 1835–1680 cm −1). Small differences in the local environment of the vanadyl ions (symmetry, defects), that can have an influence over their Lewis acidity, did not play a major role in influencing the overall product selectivity, whilst the differences in rate and turnover frequency could be explained on the basis of the differing pore diameters of the two catalysts.

Selective liquid-phase oxidation of cyclopentene over MWW type titanosilicate

The epoxidation of cyclopentene has been carried out over titanosilicate catalysts of Ti-Beta, TS-1 and Ti-MWW. Ti-MWW exhibited the highest cyclopentene conversion and epoxide selectivity with either H 2O 2 or tert-butyl hydroperoxide as an oxidizing agent. The cyclopentene conversion depended greatly on the post treatment conditions. Acid-treated but uncalcined Ti-MWW gave cyclopentene conversion twice as high as the calcined one, while the epoxide selectivity was maintained at high levels in both cases. Various techniques such as XRD, UV–vis, 29Si MAS NMR, N 2 adsorption and liquid-phase adsorption, and chemical analyses have verified consistently that the acid treatment removed the organic species located between the layers of MWW sheets, which made the interlayer entrance open and easily accessible to bulky molecules. Nevertheless, a further calcination led to a complete interlayer dehydroxyaltion and made the catalyst to be more effective for the epoxidation of linear alkenes but less active for the epoxidation of cyclic ones.

A spectroscopic study on the 12-heteropolyacids of molybdenum and tungsten (H 3PMo 12− nW nO 40) combined with cetylpyridinium bromide in the epoxidation of cyclopentene

The epoxidation of cyclopentene with hydrogen peroxide catalyzed by 12-heteropolyacids of molybdenum and tungsten (H 3PMo 12− n W n O 40, n = 1–11), 12-tungstophosphoric acid and 12-molybdophosphoric acid combined with cetylpyridinium bromide as a phase transfer reagent was carried out in acetonitrile. Among 13 heteropolyacids investigated, catalyst of H 3PMo 6W 6O 40 showed the highest activity, giving a conversion of 60% and a selectivity of 95% in the epoxidation of cyclopentene. The fresh catalysts and the catalysts under reaction condition were characterized by UV–vis, FT-IR and 31P NMR spectroscopy, which has revealed that all of the molybdotungstophosphoric acids were degraded in the presence of hydrogen peroxide to form a considerable amount of phosphorus-containing species. The active species resulted from H 3PMo 6W 6O 40 are new kinds of phosphorus-containing species, which is different from {PO 4[WO(O 2) 2] 4} 3−.