Β-alkoxy Alcohols Research Articles

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.

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.

Copper-Catalyzed Oxidative Cleavage of the C-C Bonds of β-Alkoxy Alcohols and β-1 Compounds.

Copper-catalyzed aerobic oxidation conditions were employed to promote the C–C bond cleavage of β-alkoxy alcohols and β-1 compounds (lignin model compounds). Besides these compounds, various 1,2 and 1,3-diols were successfully converted to aldehydes. We propose the Cu(I)-catalyzed mechanism explaining the C–C cleavage of these 1,2 and 1,3-dihydroxy compounds and β-alkoxy alcohols based on XPS data. Although our reaction conditions do not include large excess of bases and elaborated ligand-modified catalysts, copper salts with/without Me-TBD show good catalytic activities for C–C bond cleavage of various lignin model compounds.

Baeyer-Villiger-Including Domino Two-Step Oxidations of β-O-Substituted Primary Alcohols: Reflection of the Migratory Aptitudes of O-Substituted Alkyl Group in the Outcome of the Reaction

Following the recent development of the one-pot two-step oxidation protocol for primary β-alkoxy alcohols, additional primary β-oxy alcohols were examined under similar conditions. The outcome of these reactions closely follows the migratory aptitudes of the related α-oxy-alkyls in Baeyer-Villiger oxidation vs. that of hydrogen. Thus, these experiments helped to establish the correct order of these aptitudes for α-oxy-alkyls. Furthermore, in the case of primary β,β-dialkoxyalcohols, the formation of dialkoxymethyl formates by the domino oxidation reaction was followed by secondary reactions, forming a number of interesting products.

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.

Synthesis and structure of an air-stable bis(pentamethylcyclopentadienyl) zirconium pentafluorbezenesulfonate and its application in catalytic epoxide ring-opening reactions

An air-stable mononuclear complex of bis(pentamethylcyclopentadienyl) zirconium pentafluorbezenesulfonate was successfully synthesized by treating C6F5SO3Ag with [(CH3)5Cp]2ZrCl2, which showed the cationic uninuclear structure of [{(CH3)5Cp}2Zr(CH3CN)2(H2O)][OSO2C6F5]2·CH3CN (1) confirmed by the X-ray analysis. Complex 1 was also characterized by other techniques and found to have the good nature of air-stability, water tolerance, thermally-stability and strong Lewis-acidity. Moreover, the complex showed high catalytic activity and recyclability in catalytic epoxide ring-opening reactions by amines or alcohols. This catalytic system affords a simple and efficient approach for synthesis of β-amino alcohols or β-alkoxy alcohols.

Zirconium triflate grafted on SBA-15 as a highly efficient solid acid catalyst for ring opening of epoxides by amines and alcohols

Metal (Al, Ti, Zr) triflate grafted mesoporous SBA-15 (AlTf/S, TiTf/S, ZrTf/S) samples were synthesized as inexpensive solid acid materials by a simple one-pot-two-step synthesis methodology. These materials were characterized by X-ray diffraction, N2-sorption, thermogravimetric analysis, Fourier transform infrared spectroscopy (FT-IR), in-situ pyridine FT-IR spectroscopy, and elemental analysis. ZrTf/S was found to be a highly efficient and reusable solid acid catalyst for ring opening of epoxides with amines and alcohols and produced β-amino alcohols and β-alkoxy alcohols respectively under ambient reaction conditions. The ZrTf/S catalyst showed the highest activity, which was attributed to its high acidity compared with that of the Ti and Al containing samples.

Gadolinium-Based Metal–Organic Framework as an Efficient and Heterogeneous Catalyst To Activate Epoxides for Cycloaddition of CO2 and Alcoholysis

Development of heterogeneous catalysts for the cycloaddition of CO2 with epoxides to prepare cyclic carbonates is a hot topic in the field of CO2 transformation. Herein, a rare-earth-metal gadolinium-based metal–organic framework (Gd-MOF) was synthesized from GdCl3 and pyromellitic dianhydride in N,N-dimethylformamide, which was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption–desorption, and Fourier transform infrared (FT-IR) spectroscopy. The synthesized Gd-MOF could be used as heterogeneous catalyst for the cycloaddition of CO2 with epoxides in the presence of quaternary ammonium salts, and Gd-MOF/n-Bu4NBr showed the best performance for the cycloaddition of CO2 with various epoxides to form the corresponding cyclic carbonates due to the excellent synergetic effect. Furthermore, the prepared Gd-MOF could be used as heterogeneous catalyst for alcoholysis of various epoxides to form β-alkoxy alcohols effectively.

Salts of 1-(Chloromethyl)-DABCO: A Highly Efficient Organocatalyst for the Alcoholysis of Epoxides

Background: Epoxides are useful and important intermediates in pharmaceutical and agrochemical industries. In particular, the opening of epoxides with alcohols is an important transformation for the synthesis of β-alkoxy alcohols which are considered as valuable organic solvents, versatile synthons and intermediates. We have synthesized simple, highly efficient and environment benign catalyst and applied for the ring opening of epoxides with alcohols at room temperature. Methods: All the chemicals were purchased from commercial sources. Solvents used for the chemical synthesis were acquired from commercial sources, were of analytical grade and used without further purification. Thin layer chromatography (Merck Kiesel 60 F254, 0.2 mm thickness) was used to monitor the progress of the reactions and the compounds were purified by silica gel (60-120 mesh) column chromatography. Determination of the purity of the substrate and reaction monitoring were accomplished by GC analysis (Shimadzu GC-2010 Plus) using N2 as a carrier gas and Rtx-5 column (30 m x 0.25 mm x 0.25 mm, Restek, USA). 1H NMR (400 MHz) and 13C NMR (100 MHz) spectra were recorded on Jeol ECX FT-NMR instrument using CDCl3 as solvent and TMS as internal reference. The chemical shift values were expressed on δ scale and the coupling constant (J) in Hz. Results: The quaternary salts of 1-(chloromethyl)-DABCO was synthesised from 1-(chloromethyl)-4- aza-1-azonia-bicyclo[2.2.2]octane tetrafluoroborate and different acids in acetone at 25 °C temperature. These salts were exhibits high catalytic activity for the ring opening of epoxides and gave corresponding β-alkoxy alcohols in good to excellent yields. Styrene oxide and phenyl glycidyl ether gave completely regioselective β-alkoxy alcohol. Conclusion: We have synthesized simple, convenient, highly efficient salts of 1-(chloromethyl)- DABCO and applied as organocatalysts (0.127 mol%) for the regioselective ring opening of epoxides with methanol. Ring opening of styrene oxide with different alcohols to afforded β-alkoxy alcohols in good to excellent yields. The cyclic epoxides gave trans-2-methoxy-cyclic alcohols in excellent yields. The catalyst also catalyzed the less reactive epoxide like glycidyl ethers, epichlorohydrin required a high loading of organocatalyst 3 (2 mol%) to complete the reaction. Keywords: Alcoholysis, epoxides, salt of DABCO, alkoxy ethers, ring opening of epoxides.

An epoxide ring-opening reaction by using sol–gel-synthesized palladium supported on a strontium hydroxyl fluoride catalyst

Palladium supported on a strontium hydroxyl fluoride catalyst was synthesized by a one-pot fluorolytic sol–gel method. The prepared catalyst was characterized by various physicochemical techniques. The sol–gel method has led to the formation of a high surface area (57 m2g−1), mesoporous (pore diameter = 13.0 nm) catalyst with uniform dispersion of Pd nanoparticles of size ∼7 nm on the surface of strontium hydroxyl fluoride. The catalyst was used for epoxide alcoholysis, and 100% conversion was obtained with 96% selectivity for β-alkoxy alcohols under mild conditions. The catalyst could be recycled for up to three catalytic cycles without any appreciable decrease in conversion and selectivity, indicating the stability of the catalyst under the reaction conditions. Further, the mechanism of alcoholysis was proposed on the basis of the physicochemical characteristics of the catalyst and on the basis of the products formed during the catalytic reaction.

Catalytic alcoholysis of epoxides using metal-free cucurbituril-based solids.

Metal-free cucurbit[7]uril (CB7) solid-state assemblies promote acid-catalysed alcoholysis of aliphatic and aromatic epoxides under mild conditions to give β-alkoxy alcohols, which are important intermediates for the synthesis of a vast range of compounds such as bioactive pharmaceuticals. The catalytic process is heterogeneous and the catalyst can be reused in consecutive runs without any reactivation treatment. The acid species responsible for the catalytic activity of CB7 may be entrapped hydronium ions.

Temperature-Dependent Immobilization of a Tungsten Peroxo Complex That Catalyzes the Hydroxymethoxylation of Olefins.

A tungsten peroxo complex stabilized by the bidentate picolinato ligand has been synthesized and then immobilized successfully on imidazole-functionalized silica. The immobilized tungsten-based catalyst was employed as an efficient catalyst for the one-pot synthesis of β-alkoxy alcohols from olefins and methanol with H2 O2 . Regarding the catalyst evaluation and the results of characterization by the various methods, it was demonstrated that the immobilization of tungsten peroxo complex was highly temperature-dependent. The tungsten peroxo complex can dissociate and diffuse into the liquid phase at reaction temperature, resulting in a homogeneous reaction. Nevertheless, the catalytically active species was anchored on the imidazole-functionalized silica by hydrogen bonding as the temperature was lowered to 0 °C after the reaction, which thus offered a highly effective approach for recycling the catalyst for consecutive cycles. In addition, various olefins can be converted to the corresponding β-alkoxy alcohols with good conversion and selectivity under relative mild conditions by H2 O2 .

ChemInform Abstract: Ring Opening of Epoxides with Alcohols Using Fe(Cp)2BF4 as Catalyst.

Abstract Fe(Cp) 2 BF 4 is an efficient catalyst for the alcoholysis of aromatic, aliphatic, and cyclic epoxides giving excellent yields of the corresponding β-alkoxy alcohols under ambient conditions. The methanolysis of styrene oxide using Fe(Cp) 2 BF 4 as a catalyst (5 mol %) gave excellent yield of 2-methoxy-2-phenylethanol with complete regio-selectivity. The ring opening of cyclic epoxides gave 77–97% yields of trans -β-methoxy alcohols, in 0.5–6 h. The use of 1,2-epoxyhexane and 1,2-epoxydodecane as substrates gave both regioisomers in excellent yields. The first order rate of reaction with respect to catalyst was observed for the kinetics of ring opening of 1,2-epoxyhexane with methanol.

Graphite oxide: a simple and efficient solid acid catalyst for the ring-opening of epoxides by alcohols

A simple, efficient, and general procedure for the ring-opening of epoxides with various alcohols to give the corresponding β-alkoxy alcohols using graphite oxide (GO) as the catalyst, under very mild reaction conditions is described. The method proceeds in good to excellent yields and in short reaction times at room temperature under metal-free conditions.

Modified Montmorillonite clay catalyzed regioselective ring opening of epoxide with amines and alcohols under solvent free conditions

Modification of Montmorillonite by acid treatment depletes the layered structure and generates micro- and mesopores. The catalytic activity of naturally occurring Montmorillonite clay modified by acid treatment is reported for the reactions of epoxides with nucleophiles such as amines and alcohols at ambient temperature and solvent-free condition. The solid acid catalyst of the present study is reusable and exhibits significantly higher catalytic activities than known catalysts for the opening of the oxirane ring with nitrogen (aromatic as well as aliphatic amines) and oxygen (aromatic as well as aliphatic alcohols). A wide range of β-amino alcohols and β-alkoxy alcohols are synthesized with high epoxide conversion of excellent regioselectivity. The modified catalyst is recycled up to five times without significant loss in conversion and selectivity.

Ring opening of epoxides with alcohols using Fe(Cp)2BF4 as catalyst

Fe(Cp)2BF4 is an efficient catalyst for the alcoholysis of aromatic, aliphatic, and cyclic epoxides giving excellent yields of the corresponding β-alkoxy alcohols under ambient conditions. The methanolysis of styrene oxide using Fe(Cp)2BF4 as a catalyst (5mol%) gave excellent yield of 2-methoxy-2-phenylethanol with complete regio-selectivity. The ring opening of cyclic epoxides gave 77–97% yields of trans-β-methoxy alcohols, in 0.5–6h. The use of 1,2-epoxyhexane and 1,2-epoxydodecane as substrates gave both regioisomers in excellent yields. The first order rate of reaction with respect to catalyst was observed for the kinetics of ring opening of 1,2-epoxyhexane with methanol.

ChemInform Abstract: Efficient and Regioselective Ring‐Opening of Epoxides with Alcohols and Sodium Azide by Using Catalytic Amounts of GaCl3/Polyvinylpyrrolidone.

/PVP). This catalyst was employed for efficient and regioselective ring-opening reaction of epoxides by variousalcohols under solvent-free conditions at room temperature. In our procedure, this heterogeneous catalyst wasused at neutral and mild reaction conditions to afford high yields of β-alkoxy alcohols. Also, regioselectiveconversion of epoxides to β-azidohydrines was accomplished by sodium azide in MeOH in the presence ofGaCl

Efficient and Regioselective Ring-Opening of Epoxides with Alcohols and Sodium Azide by using Catalytic Amounts of GaCl3/Polyvinylpyrrolidone

/PVP). This catalyst was employed for efficient and regioselective ring-opening reaction of epoxides by variousalcohols under solvent-free conditions at room temperature. In our procedure, this heterogeneous catalyst wasused at neutral and mild reaction conditions to afford high yields of β-alkoxy alcohols. Also, regioselectiveconversion of epoxides to β-azidohydrines was accomplished by sodium azide in MeOH in the presence ofGaCl

Sulphated yttria–zirconia as a regioselective catalyst system for the alcoholysis of epoxides

It has been reported that sulphated yttria–zirconia efficiently catalysed the epoxide ring opening with a variety of alcohols under solvent free conditions to give corresponding β-alkoxy alcohols. In most of the cases reaction of epoxides with 1°, 2° and 3° alcohols in the presence of catalytic amounts of SO42−/YxZr1−xO2 gives exclusively one regioisomer with excellent yields. The catalysts were characterized by XRD, SEM/EDAX, total acidity and TGA. The protocol is highly efficient, regioselective, atom economical, greener and applicable for a wide range of aliphatic and aromatic epoxides and alcohols with excellent yields of the corresponding β-alkoxy alcohols. The catalysts show reusability for up to four consecutive catalytic cycles without any significant loss of catalytic activity.

Tuning of the Activity and Induction Period of the Polymerization of Propylene Oxide Catalyzed by Double Metal Cyanide Complexes Bearing β-Alkoxy Alcohols as Complexing Agents

For the development of commercially viable catalyst systems for the polymerization of propylene oxide (PO), a series of double metal cyanide (DMC) complexes have been developed by reacting aqueous zinc(II) chloride with aqueous potassium hexacyanocobaltate(III) in the presence of various complexing agents (CAs) such as 2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol, 2-butoxyethanol (BE), 1-methoxypropan-2-ol, 1-ethoxypropan-2-ol, 1-propoxypropan-2-ol, and 1-butoxypropan-2-ol (BP) with different polarities and tert-butyl alcohol (tBuOH). The catalyst composition was estimated by combining elemental analysis with thermogravimertic analysis. The coordination of the CA can be identified by employing X-ray photoelectron spectroscopy, X-ray diffraction patterns, and infrared spectroscopy of the catalysts. Pursuing a catalyst system showing favorable polymerization behavior for commercial aspects of both catalytic activity and reaction control, the kinetics of PO polymerizations were investigated by using 4...