Alcoholysis Of Epoxides Research Articles

Post-Synthetic Modification of a 1D Mixed-Linker Zn(II) Coordination Polymer for Acid-Catalyzed Alcoholysis of Epoxides.

Rational design of heterogeneous acid catalysts possessing uniform dispersion of active sites plays a significant role in the catalytic performance. In the present work, a coordination polymer, [Zn(4,4´-bpy)(µ-Hbtc)(H2O)]∙2H2O (Zn-CP), was solvothermally synthesized using 4,4´-bpy (= 4,4´-bipyridine) and H3btc (= 1,3,5-benzenetricarboxylic acid) mixed linkers. Single crystal X-ray analysis of the polymer displayed that Zn-CP chains were decorated with 4,4´-bpy having unidentate coordination fashion. Then, the free N atom of the linker in Zn-CP was functionalized by -SO3H groups to afford Zn-CP-SO3H with enhanced acidity. The structures were characterized by FT-IR, thermogravimetric analysis, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature programmed desorption of NH3 (NH3-TPD), and field emission scanning electron microscopy (FE-SEM) analyses. The coordination polymer was employed as heterogeneous catalyst for alcoholysis of epoxides under room conditions. The Zn-CP-SO3H exhibited excellent catalytic activity and regioselectivity in the methanolysis of styrene oxide within short reaction time.

1T/2H MoSe2 modified ZnIn2S4 with modulating internal electric field to boost efficient performance of photocatalytic H2 evolution and epoxide alcoholysis

Herein, the extended layer spacing 1T MoSe2 coupled with ZnIn2S4 nanosheets through in-situ growth, and ultimately obtained 1T /2H MoSe2/ZnIn2S4 photocatalysts with S-scheme heterojunction. This rational structure enables photogenerated carriers to rapidly transfer to MoSe2 via Mo-S bond. In order to further address the problem of wasted oxidative half-reaction, we rely on the dehydrogenation of benzyl alcohol as a carrier for hole depletion. Notably, optimized 1T/2H MoSe2/ZnIn2S4 has superior H2 evolution ability, reaching up to 11.271 mmol·g−1·h−1 and the apparent quantum efficiency at 420 nm is 10.3 %. Meanwhile, the conversion rate of benzyl alcohol to high value-added benzaldehyde is 60.60 %. In addition, the Zn acidic sites can achieve polarization of epoxides and precise cleavage C-O bond. Thus, it also has the ability to high selectivity and efficient photocatalytic epoxide alcoholysis. This work proposes a new insight for enhancing photocatalytic properties via regulating IEF to fabricate S-scheme heterostructure.

Modulation of the assembly fashion among metal-organic frameworks for enantioretentive epoxide activation.

Highly enantioretentive alcoholysis of epoxides is an important way to synthesize enantiopure β-alkoxy alcohols, which are irreplaceable intermediates demanded by biomedicines, fine chemicals and other industries. In this report, we exploit a series of Zr-based metal-organic frameworks (Zr-MOFs) as the catalysts to achieve high activity and enantioretentivity in the alcoholysis of styrene oxide via modulating their assembly fashions. It is explored that hcp-UiO-66 not only exhibits a ∼10 fold improved catalytic activity than both hxl-CAU-26 and fcc-UiO-66 of varied assemblies but also maintains superior product enantioretentivity. Theoretic calculations together with experimental proof discloses the origin of distinct catalytic activity caused by different assembly fashions. This assembly modulation strategy offers a potential protocol for seeking high-performance catalysts among MOFs by virtue of their rich polymorphisms.

Construction of a series of pH stable Ca-based MOFs, their CO2 adsorption and catalytic activity.

In this study, three different solvent systems have been employed to investigate the effect of reaction parameters on the synthesis of four alkaline earth metal-based MOFs namely [Ca(0.5 1,4-phenyl diacetic acid)2(H2O)DMF]∞ (Ca-MOF-1), [Ca(1,4-naphthalene dicarboxylate)DMF]∞ (Ca-MOF-2), [Ca2(0.5 1,2,4,5-benzene tetracarboxylate)2(H2O)3DMF]∞ (Ca-MOF-3) and [Ca2(2,6-naphthalene dicarboxylate)2(H2O)6]∞ (Ca-MOF-4). The crystal structures of these four MOFs have been resolved through single crystal X-ray analysis and the bulk phase purity of these MOFs was assessed using PXRD and FT-IR analysis. To check the stability of these MOFs, thermogravimetric analysis (TGA) was carried out. To analyze the robustness of these MOFs, the PXRD of the samples was also collected at different pH levels. These MOFs were further explored as Lewis acid catalysts for the alcoholysis of epoxides and the activity of these catalysts depend on the open metal sites present in the MOFs. The catalytic activity follows the order: Ca-MOF-2 > Ca-MOF-4 > Ca-MOF-1 > Ca-MOF-3. The activity was also checked with various epoxide substrates using Ca-MOF-2. Density functional theory (DFT) calculations also support this trend with the help of the thermodynamic feasibility of epoxide binding, considering model MOF structures. The weak interaction between the epoxide oxygen and the metal centre of the most stable MOF structure has also been clarified by computational studies.

Immobilization of phosphotungstic acid on the surface of chemically modified magnetite nanoparticles: An efficient heterogeneous acid catalyst for alcoholysis of epoxides

A new magnetically recoverable heterogeneous acid catalyst was easily synthesized by electrostatic interaction of phosphotungstic acid (HPW) species with 3-aminopyridine (Ampy) modified magnetite-silica heterostructure (Fe3O4/SiO2-Ampy-HPW). The step by step modification of magnetite nanoparticles along with structural stability, and maintenance of magnetization and morphology of bare magnetite nanoparticles after chemical functionalization steps were confirmed by various physicochemical techniques. The size of these nanoparticles was obtained to be 10–30 nm from TEM analysis, which was in accordance with the data estimated from XRD technique. Also, it was observed that the presence of HPW on the surface of catalyst has increased the acid content of catalyst. Catalytic property of Fe3O4/SiO2-Ampy-HPW catalyst was assessed in acid-catalyzed ring opening of epoxides with alcohols. According to the results obtained at optimum reaction condition, the prepared catalyst exhibited good performance (conversion of 93%) with high selectivity (100%) in methanolysis of styrene oxide compared to the unfunctionalized Fe3O4/SiO2, which is definitely due to the presence of HPW acidic species on the surface of Fe3O4/SiO2. Moreover, other epoxides and alcohols were tested in this catalytic system, which subsequently, reasonable results with more or less conversion were obtained based on the types of the epoxides and alcohols used.

Exposed Zinc Sites on Hybrid ZnIn2S4@CdS Nanocages for Efficient Regioselective Photocatalytic Epoxide Alcoholysis

AbstractPhotocatalytic epoxide alcoholysis through C−O bond cleavage and formation has emerged as an alternative to synthesizing anti‐tumoral pharmaceuticals and fine chemicals. However, the lack of crucial evidence to interpret the interaction between reactants and photocatalyst surface makes it challenging for photocatalytic epoxide alcoholysis with both high activity and regioselectivity. In this work, we report the hierarchical ZnIn2S4@CdS photocatalyst for epoxide alcoholysis with high regioselectivity nearly 100 %. Mechanistic studies unveil that the precise activation switch on exposed Zn acid sites for C−O bond polarization and cleavage has a critical significance for achieving efficient photocatalytic performance. Furthermore, the establishment of Z‐scheme heterojunction facilitates the interface charge separation and transfer. Remarkably, the underlying regioselective photocatalytic reaction pathway has been distinctly revealed.

Exposed Zinc Sites on Hybrid ZnIn2 S4 @CdS Nanocages for Efficient Regioselective Photocatalytic Epoxide Alcoholysis.

Photocatalytic epoxide alcoholysis through C-O bond cleavage and formation has emerged as an alternative to synthesizing anti-tumoral pharmaceuticals and fine chemicals. However, the lack of crucial evidence to interpret the interaction between reactants and photocatalyst surface makes it challenging for photocatalytic epoxide alcoholysis with both high activity and regioselectivity. In this work, we report the hierarchical ZnIn2 S4 @CdS photocatalyst for epoxide alcoholysis with high regioselectivity nearly 100 %. Mechanistic studies unveil that the precise activation switch on exposed Zn acid sites for C-O bond polarization and cleavage has a critical significance for achieving efficient photocatalytic performance. Furthermore, the establishment of Z-scheme heterojunction facilitates the interface charge separation and transfer. Remarkably, the underlying regioselective photocatalytic reaction pathway has been distinctly revealed.

Ppm-level Cu dopant on ultrathin Pd nanosheets/TiO2 for highly enhanced photocatalytic alcoholysis of epoxides

Photocatalysis provides a new avenue for organic synthesis, to which catalyst design at atomic level holds the key. Herein, the first case of ppm-level (39 ppm) Cu dopant based photocatalyst has been successfully constructed as Cu1Pd200/TiO2, in which Cu element dopes ultrathin Pd nanosheets (thickness of 2 nm) with atomic dispersion using TiO2 as the semiconductor host. The alcoholysis of styrene oxide, as a model reaction, can produce valuable β-alkoxy alcohols, conventionally requiring corrosive strong acids or harsh reaction conditions. The presence of ppm-level Cu atoms in Cu1Pd200/TiO2 can boost alcoholysis with a quite high reaction rate of 176 mmol·g−1·h−1 at room temperature under light illumination (100 mW·cm2), which is 6 times and 17 times higher than Pd/TiO2 and bare TiO2, respectively. Moreover, the Cu-doped photocatalyst presents excellent stability without deactivation after ten cycles. Based on X-ray photoelectron spectroscopy, infrared spectroscopy and control experiments, this unexpected photocatalytic behavior mainly origins from the electron transfer effect and unique chemisorption of epoxides owing to Cu dopant.

MBA-cross-linked poly(N-vinyl-2-pyrrolidone)/ferric chloride macromolecular coordination complex as a novel and recyclable Lewis acid catalyst: Synthesis, characterization, and performance toward for regioselective ring-opening alcoholysis of epoxides

A novel macromolecular-metal coordination complex, MBA-cross-linked PNVP/FeCl3 material was fabricated by immobilization of water intolerant ferric chloride onto the porous cross-linked poly(N-vinyl-2-pyrrolidone) carrier beads as a macromolecular ligand or carrier which was prepared by suspension free-radical copolymerization of N-vinyl-2-pyrrolidone (NVP) and N,N′-methylene bis-acrylamide (MBA) as a crosslinking agent in water. The obtained PNVP/FeCl3 was characterized by UV/vis and FT-IR spectroscopies, TGA, FE-SEM, EDX, and ICP techniques. This heterogenized version of ferric chloride is a convenient and safe alternative to highly water intolerant ferric chloride. The catalytic performance of (PNVP/FeCl3) as an efficient and recyclable polymeric Lewis acid catalyst was appropriately probed in the regio-and stereoselective nucleophilic ring opening of various epoxides with various alcohols in excellent yields with TOF up to 182.48 h−1 without generating any waste. The activity data indicate that this heterogeneous catalyst is very active and could be easily recovered, and reused at least six times without appreciable loss of activity indicating its stability under experimental conditions.

Cross‐linked poly(N‐vinylpyrrolidone)‐titanium tetrachloride complex: A novel stable solid TiCl4 equivalent as a recyclable polymeric Lewis acid catalyst for regioselective ring‐opening alcoholysis of epoxides

AbstractCross‐linked poly(N‐vinylpyrrolidone) resin beads were prepared as macromolecular ligand precursors by suspension copolymerization of N‐vinyl‐2‐pyrrolidone and N,N′‐methylenebisacrylamide (MBA) as a crosslinking agent in water. Subsequently, the resulting polymer carrier precursor was readily combined with titanium tetrachloride to form a stable polymeric coordination complex (PNVP/TiCl4), and this novel stable TiCl4 equivalent evaluated as a heterogeneous and reusable solid Lewis acid catalyst for the regio‐and stereoselective nucleophilic ring opening of various epoxides with various alcohols to prepare β‐alkoxy alcohols in excellent yields without generating any waste. The MBA‐cross‐linked PNVP and resultant catalyst were characterized by Fourier transform infrared spectroscopy (FT–IR), field‐emission scanning electron microscope (FE–SEM), energy dispersive X‐ray (EDX), inductively coupled plasma (ICP), and thermogravimetric analysis (TGA) techniques. Moreover, the catalyst is very stable, easily separated, and reused at least five times without significant loss of activity. In terms of scope, yields, the amount of catalyst used, and reaction time, the PNVP‐TiCl4 complex catalyst is an improvement over previously reported heterogeneous catalysts for ring opening of epoxides methods. Further, the experimental outcome revealed that using the copolymer beads as carriers with a high percentage of crosslinking and the high mesh size leads had an adverse effect on the reaction rate.

Exploring tailor-made Br\xf8nsted acid sites in mesopores of tin oxide catalyst for \u03b2-alkoxy alcohol and amino alcohol syntheses

The generation of Brønsted (Sn–OH) and Lewis (coordinatively unsaturated metal centers) acidic sites on the solid surface is a prime demand for catalytic applications. Mesoporous materials are widely employed as catalysts and supports owing to their different nature of acidic sites. Nevertheless, the procedure adopted to generate acid functionalities in these materials involves tedious steps. Herein, we report the tunable acidic sites containing Brønsted sites with relatively varied acid strength in tin oxide by employing soft template followed by simple thermal treatment at various temperatures. The readily accessible active sites, specifically Brønsted acidic sites distributed throughout the tin oxide framework as well as mesoporosity endow them to perform with exceptionally high efficiency for epoxide ring opening reactions with excellent reusability. These features promoted them to surpass stannosilicate catalysts for the epoxide ring opening reactions with alcohol as a nucleophile and the study was extended to aminolysis of epoxide with the amine. The existence of relatively greater acid strength and numbers in T-SnO2-350 catalyst boosts to produce a high amount of desired products over other tin oxide catalysts. The active sites responsible in mesoporous tin oxide for epoxide alcoholysis were studied by poisoning the Brønsted acidic sites in the catalyst using 2,6-lutidine as a probe molecule.

Metalation of Catechol-Functionalized Defective Covalent Organic Frameworks for Lewis Acid Catalysis.

Covalent organic frameworks (COFs) have emerged as a fascinating crystalline porous material and are widely used in the field of catalysis. However, developing simple approaches to fabricate conjugated COFs with specific functional groups remains a significant challenge. In this study, the construction of defective COF-LZU1 with Lewis acid sites embedded into the frameworks is fulfilled by a facile solvent-assisted ligand exchange method. A monodentate ligand, protocatechualdehyde, is successfully introduced into the skeleton of COF-LZU1, which endows the defects in the structure of COF-LZU1 via replacement of the original coordinated benzene-1,3,5-tricarbaldehyde ligand. As-synthesized defective COF-LZU1 decorated with protocatechualdehyde is rich of free hydroxy groups for chelating with active metal ions. Specifically, after combining with Fe3+ , the defective COF-LZU1 shows excellent activity in catalytic alcoholysis of epoxides under mild conditions. The method reported here will open up the opportunity to incorporate different functional groups into COFs and enrich the strategies for creating new types of porous catalysts.

A new Brønsted acid MIL‐101(Cr) catalyst by tandem post‐functionalization; synthesis and its catalytic application

A new heterogeneous Brønsted solid acid catalyst was prepared by tandem post‐functionalization of MIL‐101(Cr) and utilized for acetic acid esterification and alcoholysis of epoxides under solvent‐free conditions. First, MIL‐101(Cr) was functionalized with pyrazine to achieve MIL‐101(Cr)‐Pyz. Afterwards, the nucleophilic reaction of MIL‐101(Cr)‐Pyz with 1,3‐propane sultone and next acidification with diluted sulfuric acid gave MIL‐101(Cr)‐Pyz‐RSO3H Brønsted solid acid catalyst. Various characterization methods such as Fourier transformation infrared (FT‐IR) spectroscopy, X‐ray diffraction (XRD), elemental analysis (CHNS), X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy‐dispersiveX‐ray(EDX) spectroscopy, thermal analysis (TGA/DTA), acid–base titration, and N2 adsorption/desorption analysis were employed to fully characterize the prepared catalyst. The catalyst showed high activity compared to unmodified MIL‐101(Cr) in both catalytic acetic acid esterification and alcoholysis of epoxides. It can also be readily isolated from the reaction mixture and reused three times without major decrease in its activity.

Enhancing the Regioselectivity of B(C6F5)3-Catalyzed Epoxide Alcoholysis Reactions Using Hydrogen-Bond Acceptors

Epoxide alcoholysis is extensively employed in the synthesis of polymers and chemical intermediates, and it generally requires an acid catalyst for high rates and selectivity. Tris(pentafluoropheny...

A metal organic cage with semi-rigid ligand for heterogeneous alcoholysis of epoxides

A metal organic cage, [Cu6(L)4(DMF)2(H2O)4](1,4-Dioxane)2(DMF)10(H2O)4 (H3L = 4,4′,4″-(benzene-1,3,5-triyltris(oxy))tribenzoic acid) (FJU-18), has been constructed by six Cu2(CO2)4 paddle-wheel building units and eight semi-rigid L. The porous FJU-18 containing large cage of 1.6 nm shows high catalytic activity for the ring opening of styrene oxide in methanol at 65 °C under nitrogen atmosphere.

Lead-Free Cs3 Bi2 Br9 Perovskite as Photocatalyst for Ring-Opening Reactions of Epoxides.

Herein, an innovative approach was developed by using stable, lead-free halide perovskite for solar-driven organic synthesis. The ring-opening reaction of epoxides was chosen as a model system for the synthesis of value-added β-alkoxy alcohols, which require energy-intensive process conditions and corrosive, strong acids for conventional synthesis. The developed concept included the in situ preparation of Cs3 Bi2 Br9 and its simultaneous application as photocatalyst for epoxide alcoholysis under visible-light irradiation in air at 293 K, with exceptional high activity and selectivity ≥86 % for β-alkoxy alcohols and thia-compounds. The Cs3 Bi2 Br9 photocatalyst exhibited good stability and recyclability. In contrast, the lead-based perovskite showed a conversion rate of only 1 %. The origin of the unexpected catalytic behavior was attributed to the combination of the photocatalytic process and the presence of suitable Lewis-acidic centers on the surface of the bismuth halide perovskite photocatalyst.

Molecular mechanism of heterogeneous supramolecular catalysis of metal-free cucurbituril solid for epoxide alcoholysis

Heterogeneous and supramolecular catalysis are fundamental processes in chemistry. To understand the synergistic role between heterogeneous and supramolecular catalysis, the catalytic mechanism of cucurbituril solid for epoxide alcoholysis was investigated by performing density functional theory (DFT) calculations. The results reveal that styrene oxide (StyOx) ethanolysis has an inherent regioselectivity, which results from different groups linked to the epoxy group. The hydronium ion can catalyze the ring-opening of StyOx ethanolysis and lead to the formation of a planar carbenium ion. StyOx can also be hydrolyzed via the homogenous catalysis of acid to produce 1, 2-diol. Cucurbituril solid can catalyze epoxide alcoholysis because of its acidic property. Its unique cavity can lead to a favorable frontside-attack of the alcohol on the carbenium ion. The product from the heterogeneous catalysis of cucurbituril solid is pure β-alkoxy alcohol. The results are important to understand heterogeneous and supramolecular catalysis and the design of new and effective supramolecular catalysts.

Computation and structural elucidation of compounds formed via epoxide alcoholysis.

Isobenzofuranones are known for their wide range of biological activities such as fungicide, insecticide, and anticancer. The search for novel bioactive compounds was performed by reaction of epoxide 2 with methanol, ethanol, propan-1-ol, propan-2-ol, and butan-1-ol. The mechanism for the stereoselective and stereospecific epoxide opening with methanol was reasoned by calculating the transition states for the two putative structures (rac)-3a and (rac)-3b. The compound (rac)-3a is the kinetic product as inferred from the lower energies of its transition state (TS1). The 1 H and 13 C nuclear magnetic resonance (NMR) chemical shifts for these two candidate structures were calculated and compared with the experimental data using mean absolute error (MAE) and DP4 analyses. Therefore, the relative stereochemistry of (rac)-3a was established by the mechanism, MAE, and DP4 approaches. The hydroxyl group was acetylated to surpass the problem of signal overlapping of H5 and H6 in the 1 H NMR. The relative stereochemistry of the corresponding ester determined by NMR interpretation was in agreement with the structure of (rac)-3a.

A Linear Trinuclear Oxidodiperoxido‐molybdenum(VI) Complex with Single Triazole Bridges: Catalytic Activity in Epoxidation, Alcoholysis, and Acetalization Reactions

AbstractThe complex (Htrz)2[Mo3O6(O2)4(trz)2]⋅H2O (1), isolated from the reaction of MoO3 with H2O2 in the presence of 1,2,4‐triazole (trz), displays singular structural features such as double bridges comprising one oxido and one triazole ligand, and peripheral oxidodiperoxido‐molybdenum(VI) units. A comparative study was performed regarding the catalytic activity and stability of complex 1 and the hybrid material [MoO3(trz)0.5] (2) for the epoxidation of cis‐cyclooctene (Cy8), the alcoholysis of epoxides, and the acetalization of benzaldehyde (PhCHO). Methanol or ethanol were used as solvents and reagents for the latter two reactions. For the substrates Cy8, styrene oxide, and PhCHO, the corresponding epoxide, β‐alkoxy alcohol, and dialkyl acetal were obtained with 100 % selectivity at very high conversions. In general, 1 performed better than 2 for the different catalytic reactions. Under certain oxidant/co‐solvent conditions used for Cy8 epoxidation, 1 was converted to 2 during the reaction.

Graphene‐Oxide‐Supported SO3H‐Functionalized Imidazolium‐Based Ionic Liquid: Efficient and Recyclable Heterogeneous Catalyst for Alcoholysis and Aminolysis Reactions

AbstractIonic liquids have been established as solvents and catalysts in a number of reactions due to their unique properties. In this study, we have synthesized sulfonic acid functionalized imidazolium based strongly acidic ionic liquid supported on graphene oxide (PTS−Im‐3@GO). PTS−Im‐3@GO was synthesized by grafting 1‐(4‐sulfobutyl)‐3‐(3‐propyltriethoxysilyl)imidazolium hydrogen sulfate onto graphene oxide (GO) by covalent bonds. The prepared PTS−Im‐3@GO was used for regio‐selective ring opening reaction of styrene oxide with isopropyl alcohol giving 95% conversion and 100% regio‐selectivity towards 2‐isopropoxy‐2‐phenylethan‐1‐ol at 50 °C. The activity of the said catalyst was compared with various heterogeneous catalysts such as GO, PTS−Im‐1@GO, PTS−Im‐2@GO, PTS−Im‐1, PTS−Im‐2, PTS−Im‐3, Hβ‐zeolite, and montmorillonite K‐10. Among all catalysts, PTS−Im‐3@GO showed good conversion towards the desired product. PTS−Im‐3@GO was characterized by FTIR, SEM, EDS, TGA, XRD, 29Si NMR, XPS and CHNS analysis. Systematic studies demonstrated that PTS−Im‐3@GO had excellent catalytic activity and regio‐selectivity for the alcoholysis of epoxides rendering β‐alkoxy alcohols and aminolysis of epoxide giving β‐amino alcohols in very good yields. The protocol is clean and green.