Aliphatic Epoxides Research Articles

Aliphatic Olefin Epoxidation with Hydrogen Peroxide Catalyzed by an Integrated Mn/TS-1/N System

AbstractPropylene liquid-phase epoxidation with 50–75% H2O2 is an important process for the industrial production of propylene oxide (PO). To realize a propylene epoxidation process that proceeds with low hydrogen peroxide concentration, we developed an integrated Mn/TS-1/N catalytic system via in-situ reaction of Mn/TS-1 with an N-donor ligand, affording the PO product in excellent yield with only 30 wt% H2O2. Other long-chain aliphatic epoxides were also readily synthesized by this catalytic epoxidation system. Moreover, in addition to the standard micro-pressure reactor, a continuous-flow microreactor was developed that executed the hydrogen peroxide propylene oxide (HPPO) process with excellent efficiency for 1300 hours. This innovative Mn/TS-1/N catalyzed epoxidation represents a promising direction for advancing HPPO industrial processes, offering improved efficiency while minimizing the reliance on high concentrations of H2O2.

Solvent-free conversion of CO2 in carbonates through a sustainable macroporous catalyst

The novelty of this work consists of synthesizing and exploiting a heterogeneous catalyst containing ammonium chloride as part of the polymeric sponge sites for CO2 capture. To this aim, the polymerization of 2-acryloyl(oxyethyl)trimethylammonium chloride was performed in cryo-condition, in the presence of a crosslinking agent, obtaining a lightweight macroporous freestanding material. Its efficiency in converting aromatic and aliphatic epoxides to the corresponding carbonates was successfully proved by using proton Nuclear Magnetic Resonance (1H NMR). Remarkably, the conversion of styrene oxide (SO) to styrene carbonate (SC) reached a yield of 99 % after 24 h of reaction. The calculated yield versus the aliphatic cyclohexene oxide is 71 %. Similar results were obtained by substituting the resin counter anion with Br−, although the conversion kinetic was slower than the chloride. It is worth noticing that reactions took place in the mixture without adding the tetrabutylammonium bromide (TBAB), typically used as a co-catalyst to convert epoxides into carbonates. The recyclability of the as-prepared catalyst was evaluated for four reaction cycles, evidencing stable properties without significant depletion of CO2 capture efficiency. Most importantly, the post-cleaning of the catalytic sponge is not required to be reused. Finally, the green chemistry metrics applied to the process demonstrated that our approach significantly mitigates risks and reduces environmental impact, thus elevating the overall cleanliness of our proof of concept.

Multi-functional epoxides cross-linked collagen sponges for tissue engineering scaffolds

With the efficient cross-linking abilities and the flexible regulation abilities to the performances of cross-linked products, the multi-functional aliphatic epoxides were once widely used to cross-link the collagen-based materials in the last century. In present work, the multi-functional epoxides were used to construct and cross-link collagen sponges for tissue engineering scaffolds, which was hoped to board the theoretical system of epoxides and explore their potentials for modern applications. The bi- to tetra-functional epoxides were used to cross-link collagen solutions and establish the gel-like precursors, then using freeze-drying to form the final sponges. The SEM observed that the sponges had shown regular porous structures with a wide range of pore sizes from 160 to 440 μm. The sponges had presented the resistance to enzymatic degradation, shape-remaining ability, and reversible compressibility in aqueous environments, which all could be regulated through the functionalities of epoxides. The regulation abilities of multi-functional epoxides on the performances of sponges had been mainly achieved through the cross-linking degrees that the higher functionality of epoxides would bring higher cross-linking degree. Such higher cross-linking degrees could enhance the elastic behaviors of gel-like precursors, and improve the compressive strengths and thermal stabilities of sponges. Nevertheless, the multi-functional epoxides had barely affected the safety of collagen sponges at the cellular level according to the results of CCK8 assay and the SEM and CLSM images of L929 fibroblasts cultured on the cross-sections of sponges.Graphical abstract

Ionic liquid confined spaces controlled catalytic CO2 cycloaddition of epoxides in BMIm.ZnCl3 and its supported ionic liquid phases

Chemical fixation of CO2 to epoxides is an atom-economic and environment-benign approach to generate cyclic carbonates. Herein, we report efficient activation of the different aromatic and aliphatic epoxides at ambient reaction conditions. Our n-butyl-3-methylimidazulim trichlorozincate (BMIm.ZnCl3) ionic liquid presents higher activity with 56–95% conversion for the different aromatic and aliphatic epoxides from atmospheric pressure to 5 bar pressure at 40 °C. Small sized epoxides showed higher conversion and selectivity to cyclic carbonate as compared to bulky ones suggesting that the large epoxide substrates restricted diffusion into the confined spaces of BMIm.ZnCl3 IL, which limited the access of reactants to the catalytic active sites. By supporting the IL on the simple commercial SiO2, the confined SILP-ZnCl3 catalyst boosted the activity with maximum conversion and yield (99%) to cyclic carbonates under 10 bar at 100 °C. This higher performance could be attributed to the formation of the IL-cages onto SiO2 that enhances the local charge density and modulates the orientation of the IL near the surface to assist substantial charge transfer, leading to surface polarization and specific adsorption to ions. The reaction exemplifies a rare mechanism, supplemented by ex-situ ESI-MS analysis, in which epoxide 'O' is strongly H-bonded to the C2-H of imidazolium cation, while the ZnCl3 anion acts as nucleophile to facilitate the ring opening without its dissociation in chloride anion and ZnCl2, contrasting to the previous reports.

Metal- and solvent-free synthesis of 2-benzyl-3-arylquinoline using a pseudo-three-component reaction

A highly efficient and straightforward synthetic protocol for the synthesis of 2-benzyl-3-arylquinoline derivatives is developed from aryl amines and styrene oxides in the presence of 20 mol% p-toluenesulfonic acids under metal- and solvent-free conditions by employing a pseudo-three-component reaction. Using similar reaction conditions, the synthesis of 2,3-dialkylquinoline derivative can also be accomplished using aliphatic epoxide. The methodology has several advantages such as ease to handle, a broad substrate scope, good yields, metal- and solvent-free reaction conditions, and the formation of one CN and two CC bonds in a single step.

Chalcopyrite UiO-67 metal-organic framework composite for CO2 fixation as cyclic carbonates

The conversion of greenhouse gas carbon dioxide (CO2) into cyclic carbonates which are, used as green solvents and are considered sustainable substitution to toxic chemicals, can be a competent approach to net zero-emission. This work successfully incorporated Chalcopyrite (CuFeS2) in UiO-67 (University of Oslo-67) to form a composite Ch@UiO-67 using a solvothermal method. After characterization by powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FT-IR), N2 adsorption isotherm, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), Field Emission Scanning Electron Microscopy- Energy Dispersive Spectroscopy (FESEM-EDS) and Inductively coupled plasma mass spectrometry (ICP-MS), Ch@UiO-67 was tested for CO2 uptake and as a catalyst in the cycloaddition reaction of styrene epoxide (SO) with CO2 to produce cyclic carbonates, in comparison to pristine UiO-67. Ch@UiO-67 was found to be more effective as a catalyst than pristine UiO-67. This catalyst was also successful with different aromatic and aliphatic epoxides for cycloaddition with CO2 and was efficiently recycled for seven consecutive cycles without a noticeable deficit in the catalytic activity.

Improving and stabilizing fluorinated aryl borane catalysts for epoxide ring-opening

Epoxide ring-opening is a key reaction in organic chemistry. We have previously shown that B(C6F5)3, a strongly Lewis acidic arylborane, exhibited high rates and unusual selectivities for catalyzing the ring-opening of aliphatic epoxides with alcohols. Here we compare catalysts of the form B(C6H5−XFX)3 (x = 5, 4, 3, and 0) and determine that moderately Lewis acidic arylboranes have higher regioselectivity, but slower rates in this reaction. At high temperatures, these arylboranes can also hydrolyze into inactive species. However, deactivation is suppressed in the presence of co-catalytic amounts of 1,2-propanediol, and DFT calculations suggest a role for arylborane-H2O-diol complexes. Thermal stabilization and regioselectivity enhancement by diol are both more pronounced for B(C6F5)3 than for less Lewis acidic B(C6HF4)3 and B(C6H2F3)3 catalysts. These results further demonstrate the catalytic relevance of H-bound networks of arylboranes and diols and enable their use at higher temperatures and greatly increased rates.

TfOH/Hexafluoroisopropanol-Promoted Friedel–Crafts Reaction of Arenes with Aliphatic Epoxides or Alcohols

TfOH/Hexafluoroisopropanol-Promoted Friedel–Crafts Reaction of Arenes with Aliphatic Epoxides or Alcohols

Bifunctional organoboron-phosphonium catalysts for coupling reactions of CO2 and epoxides.

Recent years have witnessed intensive research activity in exploring novel metal-free organocatalysts for catalyzing the coupling reactions of CO2 and epoxides to afford cyclic or polymeric carbonates. In this direction, herein we report a series of boron-phosphonium organocatalysts for catalyzing the coupling reactions of CO2 and epoxides. These organophosphonium catalysts were synthesized in high yields by following a two step protocol involving Menschutkin and hydroboration reactions in succession. The purity of these organocatalysts was confirmed by spectroscopic techniques like 1H, 13C and 31P NMR, and molecular structures were confirmed by single crystal X-ray diffraction studies. We have also demonstrated that these bifunctional organoboron-phosphonium catalysts are comparatively much less hygroscopic compared to the analogus ammonium catalysts. These phosphonium organocatalysts were shown to catalyze the copolymerization of CO2 and cyclohexene oxide or vinyl cyclohexene oxide to provide polycarbonates with >99% polymer selectivity and carbonate linkages. The coupling reactions of aliphatic epoxides such as PO, having lower energy barrier to cycloaddition formation compared to alicyclic epoxides, preferentially provided cyclic carbonates in good yields. It was demonstrated that these organoboron-phosphonium catalysts are sensitive to chain transfer agents like water, and hence are deactivated in its presence. This is opposite to what is observed for metal based catalysts for these transformations, where water serves as a precursor to the chain-transfer agent diols.

Unlocking the Friedel-Crafts arylation of primary aliphatic alcohols and epoxides driven by hexafluoroisopropanol

Unlocking the Friedel-Crafts arylation of primary aliphatic alcohols and epoxides driven by hexafluoroisopropanol

Cellulose sulfate: An efficient heterogeneous catalyst for the ring-opening of epoxides with alcohols and anilines

Cellulose sulfate was synthesized by esterification of α-cellulose with concentrated sulfuric acid at −10°C in ethanol. Cellulose is mainly sulfated on 3-, 6- and 3, 6-positions of the cellulose. It acts as a heterogeneous catalyst for the ring-opening of epoxides with alcohols or anilines and the Friedel-Crafts reaction between N-benzylindole and crotonaldehyde at room temperature. Methanolysis of cyclic epoxides, styrene oxide, terminal aliphatic epoxides, and glycidyl ethers were carried out using the catalyst (0.4–6.8 mg/mmol of epoxide) and afforded the corresponding products in 53–97% isolated yields after 10 min–24 h. Cellulose sulfate was successfully recycled and reused up to 3 catalytic cycles for the ring-opening of styrene oxide with methanol.

Polybenzoxazine intrinsically installed N-methylpyridinium iodide functions efficient organocatalyst for CO2 fixation into cyclic carbonate

Polybenzoxazine containing N-methylpyridinium iodide (PBz-[PyMe]I) was first utilized as an efficient catalyst for CO2 fixation into cyclic carbonates. The polymer structure was determined as a phenolic-type polybenzoxazine characterized by FT-IR, 1H NMR. PBz-[PyMe]I shows a wide scope of substrates for the reaction of cycloaddition of CO2 with epoxides including aliphatic epoxides, styrene oxide derivatives, glycidyl ethers, and spiro-epoxyoxindole at 120 °C within two hours, and obtains high yields up to 96%. The catalyst was recycled up to four times remaining 82% catalytic activity comparing to the first run. A combined hydrogen-bonding mechanism activated by both phenol and pyridinium salt was proposed and verified. The synthesis and application of PBz-[PyMe]I suggested the viability of other catalytic moieties could be introduced into polybenzoxazine.

Ytterbium(III) triflate catalyzed domino reaction of arylamines and styrene oxides: Synthesis of 2-benzyl-3-arylquinoline derivatives

An efficient and straightforward method for the synthesis of 2-benzyl-3-arylquinoline derivatives is reported involving the domino reaction of substituted arylamines and styrene oxides in the presence of 10 mol% ytterbium(III) triflate in acetonitrile at 80 °C. Additionally, the reaction of aliphatic epoxides with p-anisidine provided 2,3-dialkylquinoline derivatives under identical reaction conditions. Important features of the protocol are ease of handling, broad substrate scope, good yields, and the formation of two CN and two CC bonds.

Selective palladium nanoparticles-catalyzed hydrogenolysis of industrially targeted epoxides in water

Palladium nanoparticles, with core sizes of ca. 2.5 nm, were easily synthesized by chemical reduction of Na2PdCl4 in the presence of hydroxyethylammonium salts and proved to be efficient for the selective hydrogenolysis of various aromatic, alkylphenyl, aliphatic epoxides in water as green solvent. Capping agents of the metal species were screened to define the most suitable micellar nanoreactors on two target substrates of industrial interest, epoxystyrene and 7,8-epoxy-2-methoxy-2,6-dimethyloctane. In our conditions, the hydrogenolysis of epoxystyrene proved to be pH-dependent, producing either the diol under acidic conditions, or the sweet-smelling 2-phenylethanol in the presence of a base. Promisingly, 7,8-epoxy-2-methoxy-2,6-dimethyloctane was completely and selectively hydrogenated into Florsantol®, a sandalwood odorant at a multigram scale (40 g and up to 175g). A general mechanism for the palladium nanoparticles-catalyzed hydrogenolysis of terminal epoxides was proposed according to steric and electronic properties and finely corroborated with deuterium labelling experiments.

Effect of Aromatic/Aliphatic Structure and Cross-Linking Density on the Thermal Conductivity of Epoxy Resins

High thermal conductivity polymers are in great demand as thermal management materials. However, the thermal conductivity of polymers is typically low, ∼0.2 W/(m K), and a predictive understanding of the relationship between the thermal conductivity and the molecular structure of polymers is not yet established. In this work, 14 epoxy resin thermosets are synthesized from one aliphatic epoxide and one aromatic epoxide with seven amine hardeners. These thermosets are used to systematically examine the dependence of the thermal conductivity on the molecular structure of the epoxide and the hardener. In general, aromatic structures have a higher thermal conductivity than aliphatic structures. Moreover, naphthalene-based hardeners provide the highest thermal conductivity, 0.34 W/(m K), 230% higher than the lowest thermal conductivity among the 14 epoxy resin thermosets. The cross-linking density is controlled by mixing different molar ratios of diamine and triamine and does not influence the thermal conductivity, volumetric heat capacity, density, or longitudinal speed of sound. Measured thermal conductivities of 14 epoxy resins lie between 50 and 115% of the prediction of the minimum thermal conductivity model.

Functionalization of Chitosan Oligomers: From Aliphatic Epoxide to Cardanol-Grafted Oligomers for Oil-in-Water Emulsions.

Hydrophobically modified chitooligosaccharides (COSs) were tested for suitability as an emulsifier in cationic bituminous emulsions. COSs with polymerization degrees (DPs) of 5, 10, 15, and 20 were obtained by nitrous acid deamination. A complete study on depolymerization and precise product and side product characterization was undergone. Chemical modification of COSs was performed to achieve amphiphilic structures using three fatty epoxides with a growing chain length butyl (C4), octadecyl (C9), and hexadecyl glycidyl ether (C16)). The grafting efficiency according to reaction conditions was established. Different substitution degrees (DSs) were obtained by modulating the ratio of fatty epoxy to NH2. It was shown that after a certain DS, the oligomers thus formed were not water-soluble anymore. At the end, cardanol glycidyl ether was grafted on DP 5, 10, and 15 COSs, cardanol being a biobased compound extracted from cashew nut shell; this reaction led to a potentially fully biobased structure. Water-soluble candidates with a higher DS were used as surfactants to emulsify motor oil as a simulation of bitumen. Cardanol-chitosan-based surfactants led to direct oil-in-water emulsion (60/40 w/w) composed of particles of 15 μm average size that were stable at least for 24 h.

Facile Amberlyst A-21 catalyzed access of β-hydroxynitriles via epoxide opening in water

β-Hydroxynitriles are essential intermediates in the synthesis of diverse bioactive compounds and clinical drugs. One of the precursor reactions to these intermediates is the opening of an epoxide ring with a cyanide nucleophile. In the present study, we report a milder and safer route to β-hydroxynitriles employing recyclable, Amberlyst A-21 resin in the ring-opening of epoxides with acetone cyanohydrin in water. A diverse range of substrates (fifteen), including aromatic epoxides, phenoxy epoxides, non-terminal, and terminal aliphatic epoxides, are investigated under the optimized conditions to afford the desired β-hydroxynitriles in good to excellent yield. In addition to this, the recyclability of the Amberlyst A-21 resin is also successfully demonstrated. This relatively safer methodology has the potential to be explored in other organic transformations.

Regioselective Cross-Electrophile Coupling of Epoxides and (Hetero)aryl Iodides via Ni/Ti/Photoredox Catalysis.

A cross-electrophile coupling reaction of epoxides and (hetero)aryl iodides that operates via the merger of three catalytic cycles involving a Ni-, Ti-, and organic photoredox catalyst has been developed. Three distinct classes of epoxides, styrene oxides, cyclic epoxides, and terminal aliphatic epoxides, all undergo coupling in moderate to good yield and high regioselectivity with the use of three different nitrogen-based ligands for Ni under otherwise identical reaction conditions. The mild reaction conditions accommodate a broad scope of abundant and complex coupling partners. Mechanistic studies suggest that when styrene oxides are employed radical intermediates are involved via Ti-radical ring-opening of the epoxide. Conversely, for terminal aliphatic epoxides, involvement of an iodohydrin intermediate enables the formation of the unexpected linear product.

Sc(OTf)3-Mediated One-Pot Synthesis of 2,3-Disubstituted Quinolines from Anilines and Epoxides.

Here, we report the first synthesis of 2,3-disubstituted quinolines from anilines and aromatic or aliphatic epoxides. This reaction utilizes Sc(OTf)3 as a Lewis acid and TEMPO as an oxygen scavenger. A wide variety of highly substituted quinolines were obtained with moderate to excellent yields (up to 96%).

Synthesis and characterization of polyisobutylene telechelic prepolymers with epoxide functionality

Syntheses of novel polyisobutylene telechelic prepolymers with various types of epoxide functionality, including aliphatic glycidyl ether, phenyl glycidyl ether, non-glycidyl aliphatic epoxide, and cycloaliphatic epoxide have been developed. The polyisobutylene prepolymers with aliphatic and phenyl glydicyl ether functionalities were achieved by reaction of primary alcohol-terminated and phenol-terminated polyisobutylene, respectively, with epichlorohydrin. Exo-olefin epoxide-terminated polyisobutylene was synthesized by direct epoxidation of exo-olefin-terminated polyisobutylene with a strong oxidizing agent, meta-chloroperoxybenzoic acid. The cycloaliphatic epoxide-terminated polyisobutylene was obtained by nucleophilic substitution of primary bromide end-functional polyisobutylene with a pre-formed potassium cyclohex-3-enecarboxylate salt, followed by epoxidation with meta-chloroperoxybenzoic acid. 1H NMR and MALDI-TOF mass spectrometry analyses demonstrated that the functionality for all types of epoxide prepolymers was 2.0. Gel permeation chromatography (GPC) analysis showed that targeted molecular weight and narrow molecular weight distribution were achieved for these prepolymers and no polymer chain degradation or coupling occurred during post-polymerization modifications.