Facile Esterification Research Articles

Organocatalytic synthetic route to esters and their application in hydrosilylation process

A facile esterification of α,β-unsaturated aldehydes with alcohols has been developed for the synthesis of esters by using bulky N-heterocyclic (NHC) carbene as a metal-free and eco-friendly organocatalyst. This new protocol has been proved to be effective with a wide substrate scope, giving selective esters in yields greater than 84% under mild conditions. Moreover, proposed synthetic strategy enables modification of various types of silsesquioxanes (SQ) which cannot or are technically difficult to be carried out with known protocols. For the first time, a one-pot sequential esterification/hydrosilylation has been successfully carried out.

Synthesis of polymerizable betulin maleic diester derivative for dental restorative resins with antibacterial activity

ObjectiveBisphenol A glycidyl methacrylate (Bis-GMA) is of great importance for dental materials as the preferred monomer. However, the presence of bisphenol-A (BPA) core in Bis-GMA structure causes potential concerns since it is associated with endocrine diseases, developmental abnormalities, and cancer lesions. Therefore, it is desirable to develop an alternative replacement for Bis-GMA and explore the intrinsic relationship between monomer structure and resin properties. MethodsHere, the betulin maleic diester derivative (MABet) was synthesized by a facile esterification reaction using plant-derived betulin and maleic anhydride as raw materials. Its chemical structure was confirmed by 1H and 13C NMR spectra, FT-IR spectra, and HR-MS, respectively. The as-synthesized MABet was then used as polymerizable comonomer to partially or completely substitute Bis-GMA in a 50:50 Bis-GMA: TEGDMA resin (5B5T) to formulate dental restorative resins. These were then determined for the viscosity behavior, light transmittance, real-time degree of conversion, residual monomers, mechanical performance, cytotoxicity, and antibacterial activity against Streptococcus mutans (S. mutans) in detail. ResultsAmong all experimental resins, increasing the MABet concentration to 50 wt% made the resultant 5MABet5T resin have a maximum in viscosity and appear dark yellowish after polymerization. In contrast, the 1MABet4B5T resin with 10 wt% MABet possessed comparable shear viscosity and polymerization conversion (46.6 ± 1.0% in 60 s), higher flexural and compressive strength (89.7 ± 7.8 MPa; 345.5 ± 14.4 MPa) to those of the 5B5T control (48.5 ± 0.6%; 65.7 ± 6.7 MPa; 223.8 ± 57.1 MPa). This optimal resin also had significantly lower S. mutans colony counts (0.35 ×108 CFU/mL) than 5B5T (7.6 ×108 CFU/mL) without affecting cytocompatibility. SignificanceIntroducing plant-derived polymerizable MABet monomer into dental restorative resins is an effective strategy for producing antibacterial dental materials with superior physicochemical property.

Novel Porous Organic Polymer Catalyst with Phosphate and Sulfonic Acid Sites for Facile Esterification of Levulinic Acid.

Biomass-derived value-added materials such as levulinic acid (LA) are favorable natural resources for producing ester-based biolubricants owing to their biodegradability, nontoxicity, and excellent metal-adhering properties. However, highly active catalysts must be developed to carry out efficient esterification of LA with aliphatic alcohols, especially long-chain aliphatic alcohols. In this study, we developed a novel porous covalent organic polymer catalyst (BPOP-SO3H) with dual acid sites, phosphate and sulfonic acid sites, for the esterification of LA. The prepared BPOP-SO3H catalyst was verified using various surface analysis techniques. BPOP-SO3H exhibited 98% LA conversion with n-butanol and 99% selectivity for butyl levulinate ester within 30 min, which is superior to that of most reported catalysts. BPOP-SO3H also showed high LA conversion and ester selectivity when other aliphatic alcohols were used. Moreover, BPOP-SO3H showed good recyclability for five consecutive cycles. We believe that incorporating a high density of acid sites into a porous polymer with a large surface area and hierarchical pores is a promising approach for developing heterogeneous acid catalysts for the production of alkyl levulinate esters from LA.

Tin(II) Chloride-Catalyzed Direct Esterification and Amidation of tert-Butyl Esters Using α,α-Dichlorodiphenylmethane Under Mild Conditions.

A practical one-pot synthesis of esters and amides from tert-butyl esters via acid chloride was developed. Reactions of tert-butyl esters with α,α-dichlorodiphenylmethane as the chlorinating agent and SnCl2 as catalyst-generated acid chloride intermediates in situ were subsequently used in reactions with a variety of alcohols and amines to afford the corresponding esters and amides in high yields under mild reaction conditions. This catalytic synthetic procedure offers an effective strategy for the facile esterification and amidation of tert-butyl esters.

Construction of durable and original color constancy photochromic cotton fabrics by a facile esterification strategy

Cotton-based photochromic textiles have emerged as a representative smart textile, yet constrained by the complicated process, deep original color and limited durability in practical applications. Here, spiropyran (SP) with a simple carboxy linking group was directly covalently immobilized onto cotton fabric through a facile and effective esterification strategy. Benefit from the simple structure, this modification process does not affect the basic properties and color of the fabric. In addition, the SP-cotton fabrics exhibited excellent reversible photochromic properties from colorless to violet and allowed to print exquisite patterns with long-distance control by switching light resource and photomasks. Moreover, the stable ester covalent bond endowed these SP-cotton fabrics with appropriate washing fastness and photo fatigue resistance. This study not only added value to cotton, but also paved a rational and general approach for the construction of durable and original color constancy photochromic textiles, providing a potential candidate for brand protection, anti-counterfeiting, and fashion textiles. • A novel photochromic fabric was prepared by directly covalently immobilizing spiropyran (SP) contained carboxy linking group. • A simple and extensible immobilized strategy was proposed for constructing original color constancy photochromic textiles. • SP cotton with photochromic performance from colorless to violet and allowed to print patterns with long-distance control.

Redox-responsive self-assembled polymeric nanoprodrug for delivery of gemcitabine in B-cell lymphoma therapy

Gemcitabine, as a standard and classic strategy for B-cell lymphoma in the clinic, is limited by its poor pharmacodynamics. Although stimuli-responsive polymeric nanodelivery systems have been widely investigated in the past decade, issues such as complicated procedures, low loading capacity, and uncontrollable release kinetics still hinder their clinical translation. In view of the above considerations, we attempt to construct hyperbranched polyprodrug micelles with considerable drug loading via simple procedures and make use of the particularity of the tumor microenvironment to ensure that the micelles are “inactivated” in normal tissues and “activated” in the tumor microenvironment. Hence, in this work, a redox-responsive polymeric gemcitabine-prodrug (GEM-S-S-PEG) was one-pot synthesized via facile esterification and acylation. The self-assembled subsize (< 100 nm) GEM-S-S-PEG (GSP NPs) with considerable loading capacity (≈ 24.6%) exhibited on-demand and accurate control of gemcitabine release under a simulated tumor microenvironment and thus significantly induced the apoptosis of B-cell lymphoma in vitro. Moreover, in the A20 tumor xenograft murine model, GSP NPs efficiently decreased the expansion of tumor tissues with minimal systemic toxicity. In summary, these redox-responsive and self-assembling GSP NPs with a facile one-pot synthesis procedure may hold great potency in clinical translation for enhanced chemotherapy of B-cell lymphoma. Statement of significanceA redox-responsive polymeric gemcitabine-prodrug (GEM-S-S-PEG) was one-pot synthesized via facile esterification and acylation.The self-assembled subsize (< 100 nm) GEM-S-S-PEG (GSP NPs) exhibited significant tumor therapeutic effects in vitro and in vivo.The polyprodrug GEM-S-S-PEG prepared in this study shows the great potential of redox-responsive nanodrugs for antitumor activity, which provides a reference value for the optimization of the design of functional polyprodrugs.

Nonionic nontoxic antimicrobial polymers: indole-grafted poly(vinyl alcohol) with pendant alkyl or ether groups

A series of new nonionic antimicrobial polymers with a biodegradable polyvinyl alcohol (PVA) backbone grafted with indole units and different hydrophobic alkyl or ether groups were synthesized by facile esterification.

Ionic liquid infused starch-cellulose derivative based quasi-solid dye-sensitized solar cell: exploiting the rheological properties of natural polymers

Starch and cellulose have long been used in various industrial applications as gelating agents. In this work, the intrinsic adhesive properties of these biopolymers are exploited for application as electrolytes in DSSC. Firstly, potato starch was chemically modified into phthaloyl starch in a facile esterification process. Fabrication of polymer electrolyte with phthaloyl starch (PhSt) and hydroxyethyl cellulose (HEC) incorporated with dimethylformamide and tetrapropylammonium iodide produced homogeneous gels with diminished crystallinity. Infusion of different weight percentages of 1-butyl-3-methylimidazolium iodide (BMII) into the gels were revealed to further suppress polymer crystallinity and elevate ionic conductivity. Rheological analysis revealed that addition of up to 6 wt% of ionic liquid aid in elevating the rigidity, strength and tackiness of the gels. The improved adhesiveness of the gels can be correlated to effective reduction of interfacial resistance and restraining of recombination reactions based on electrochemical impedance spectroscopy. Quasi-solid DSSC fabricated with PhSt-HEC with 8 wt% of BMII exhibited enhanced short-circuit current density, JSC and fill factor, contributing to an optimized efficiency of 5.20%.

Novel phosphorus/nitrogen/boron-containing carboxylic acid as co-curing agent for fire safety of epoxy resin with enhanced mechanical properties

It is a great challenge to develop a high-efficiency reactive flame retardant, applied to anhydride-cured epoxy resin (EP) system, simultaneously possessing good compatibility with matrix and mechanical reinforcement. In this respect, we successfully synthesized a novel phosphorus/nitrogen/boron-containing carboxylic acid (TMDB) through the facile esterification and addition reaction among 1,3,5-tris(2-hydroxyethyl)isocyanurate (THEIC), maleic anhydride (MAH), 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and boric acid (BA). TMDB was utilized as a co-curing agent for EP/methyltetrahydrophthalic anhydride (MeTHPA) system and finally cured EP behaved great transparency, suggesting excellent compatibility of TMDB with EP. Compared with pure EP, modified EP exhibited comparable thermal stability and heat resistance but higher flame retardance. With only 15.1 wt% TMDB loading, the LOI value of anhydride-cured EP increased to 29.6% from 20.1% of pure EP, and UL-94 V-0 rating was achieved. The peak heat release rate (PHRR), total heat release (THR) and total smoke production (TSP) remarkably decreased by 58.5%, 41.7% and 47.2% compared with that of pure EP, respectively. Besides, different measurements revealed TMDB simultaneously functioned in the condensed and gaseous phase during combustion. Furthermore, after incorporation of TMDB, mechanical properties of cured EP were improved and the maximum increments of flexural and tensile strength can reach 11.8% and 61.4%, respectively.

Boosting the electrochemical performance of nitrogen-oxygen co-doped carbon nanofibers based supercapacitors through esterification of lignin precursor

A facile esterification and electrospinning method is utilized to convert the waste lignin into nitrogen-oxygen co-doped esterified lignin/polyacrylonitrile based carbon nanofibers (E-CNFs). The analysis of FTIR and H 1 -NMR shows that the esterification reaction occurs between the hydroxyl group and the anhydride group and the ester bond is established in precursor. The lignin after esterification has lower glass transition temperature (Tg), and hence the obtained E-CNFs exhibit inter-fiber bonding structure, higher heteroatom content, and better wettability, rendering an efficient electron transport network and contributing pseudo capacitance. Such unique structure and morphology endow E-CNFs electrode with ultra-high specific capacitance of 320 F g −1 at 1 A g −1 and 200.4 F g −1 at 20 A g −1 with 6 M KOH aqueous as electrolyte, revealing outstanding rate capability. Moreover, the assembled E-CNFs//E-CNFs symmetric supercapacitors using 1 M Na 2 SO 4 aqueous as electrolyte deliver a high coulombic efficiency of 112.5% at the current density 1 A g −1 , a remarkable energy density of 17.92 Wh kg −1 at the power density of 800 W kg −1 , and excellent cycling stability (∼5.5% loss after 5000 cycles). This inter-fiber bonding structure control strategy provides a perspective and avenue for the further development of high-performance electrode material for supercapacitors applications. High performance supercapacitors are fabricated by carbon nanofibers with inter-fiber bonding structure as electrode materials using a facile esterification and electrospinning method. • By change the molecular microstructure to control macroscopic properties. • Building inter-fiber bonding structure to reduce resistance of electrode materials. • Elucidated the mechanism between micromorphology and electrochemical properties.

Green flame-retardant flexible polyurethane foam based on cyclodextrin

Flexible polyurethane (PU) foam is one of the most versatile materials, which has a widely range of applications. However, flexible PU foam it is easily ignitable and highly flammable. This study developed a kind of post-modification method to prepare inherent FR PU foam, which use β-CD as chain extender and introduce FR additive through a facile esterification between phosphoric acid and β-CD moiety in PU foams. The morphology and elasticity of PU still maintained after the modification of PU. β-CDs, as a bio-resources, can not only act as polyol carbon sources to promote carbon formation, but also crosslinked with phosphate ester and PU matrix through P–O–C bonds to form compact carbon layer during the combustion. This dense carbon layer effectively isolates the heat source of the flame, resulting in great improvement of combustion resistance. The time to ignition for 15% CD-H3PO4-PUF foam reached 152 s, which was over 10 times longer than that of pure PU foams. And the foam immediately self-extinguished when the flame was removed. The THR of 15% CD-H3PO4-PUF foam decreased by 70.43% compared to that of neat PU foam. The significant delay of TTI and reduction of THR can reduce the hazards of flame spread greatly.

AIE-active fluorescent polymeric nanoparticles about dextran derivative: preparation and bioimaging application

Aggregation-induced emission (AIE), as a special phenomenon of fluorescence, can elegantly overcome the fluorescence quenching caused by common fluorescent materials under high concentration conditions and has attracted interest of researchers in many fields. Particularly AIE-active polymer nanoparticles have been widely utilized in a modern biomedical research. In this work, we prepared a novel kind of AIE-active fluorescent polymeric nanoparticals (Dex-OH-CHO) through a facile esterification between a new hydrophobic AIE-active 1, 8-naphthalimide derivative and the hydrophilic dextran. The structure and optical properties of Dex-OH-CHO were characterized in detail by FTIR, 1H NMR, XPS, TEM and fluorescence spectra. The results showed that Dex-OH-CHO emitted light-blue fluorescence in aqueous solution with high fluorescent quantum yield (Φ = 24.43%, concentration is 20 μg/mL), low CMC (5 μg/mL), good photostability, high water solubility and well dispersivity. Moreover, good biocompatibility and ideal cell uptake made Dex-OH-CHO had a great application potential in biological imaging.

Reduction responsive liposomes based on paclitaxel-ss-lysophospholipid with high drug loading for intracellular delivery

In this report, a novel redox-responsive liposomes based on disulfide derivative paclitaxel-ss-lysophosphatidylcholine prodrug (PTX-ss-PC) with high PTX loading was developed for triggering drug release. First of all, PTX-ss-PC was synthesized by a facile esterification and verified by MS, 1H NMR and HPLC. After that, PTX-ss-PC derived liposomes (PTX-ss-PC liposomes) containing EPC:Chol:mPEG2000-DSPE components were prepared by the conventional film method. Moreover, physicochemical characterizations of the PTX-ss-PC liposomes were carried out by using transmission electron microscope (TEM), dynamic light scattering (DLS) and release test. It was demonstrated that the PTX-ss-PC liposomes possessed average diameter of 234.9 nm and zeta potential of −29.1 mV with highest PTX loading 7.97%. The PTX-ss-PC liposomes dissociated rapidly in a reduction medium, as confirmed by their triggered aggregation/disruption and rapid release of PTX in the presence of glutathione (GSH). Finally, in vitro cytotoxicity of the liposomes was checked against MCF-7 and A549 cells. It was found that the PTX-ss-PC liposomes exhibited favorable GSH-mediated anti-proliferative activity in comparison with the nonresponsive counterpart. Taken together, the novel PTX-ss-PC based liposomes possess improved loading capacity, reduction triggered release of PTX and efficient anti-proliferative activity, which should be valuable for further preclinical evaluation.

Facile Esterification of Degraded and Non‐Degraded Starch

AbstractThe iodine‐catalyzed esterification (acetylation and propionation) and esterification with longer fatty acids of white dextrins (degraded starches) and “waxy potato” starch containing more than 95% amylopectin are reported. The degree of substitution can be finely tuned by a simple variation of the catalyst versus the amount of anhydroglucose units. Longer fatty acids can be readily converted using 1‐methylimidazole as a solvent. The esterified carbohydrates are attractive for industrial purposes, offering high functionality, a broad variety of functional groups, high solubility, and a unique rheological behavior.

Facile synthesis of diphenylmethyl esters from 2-diphenylmethoxypyridine using catalytic boron trifluoride·diethyl etherate

A practical method for the direct preparation of diphenylmethyl (DPM) esters from 2-diphenylmethoxypyridine is described. The reaction was readily performed in the presence of a catalytic amount of boron trifluoride-diethyl etherate at room temperature. Using this reaction protocol, various carboxylic acids were converted to DPM esters with high yields. This method is highly effective for the protection of carboxylic acids and the synthesis of DPM esters, and offers a promising approach for facile esterification of a variety of carboxylic acids.

Liposomes of dimeric artesunate phospholipid: A combination of dimerization and self-assembly to combat malaria

Artemisinin and its derivatives are highly effective drugs in the treatment of P. falciparum malaria. However, their clinical applications face challenges because of short half-life, poor bioavailability and growing drug resistance. In this article, novel dimeric artesunate phospholipid (Di-ART-GPC) based liposomes were developed by combination of dimerization and self-assembly to address these shortcomings. Firstly, Di-ART-GPC conjugate was synthesized by a facile esterification of artesunate (ART) and glycerophosphorylcholine (GPC) and confirmed by MS, 1H NMR and 13C NMR. The conjugate was then assembled to form liposomes without excipient by thin film hydration method. The assembled Di-ART-GPC liposomes have typical multilamellar vesicle structure with bilayer morphology as determined by transmission electron microscopy (TEM) and cryogenic electron microscopy (cryo-EM). Moreover, the liposomes displayed an average hydrodynamic diameter of 190 nm and negative zeta potential at −20.35 mV as determined by Zetasizer. The loading capacity of ART was calculated approximately 77.6% by weight with this liposomal formulation after a simple calculation. In vitro drug release and degradation results showed that the Di-ART-GPC liposomes were stable in neutral physiological conditions but effectively degraded to release parent ART in simulated weakly acidic microenvironment. In vivo pharmacokinetics study revealed that Di-ART-GPC liposomes and conjugate have longer retention half-life in bloodstream. Importantly, Di-ART-GPC liposomes (IC50 0.39 nM) and the conjugate (IC50 1.90 nM) demonstrated excellent in vitro antiplasmodial activities without causing hemolysis of erythrocytes, which were superior to free ART (IC50 5.17 nM) and conventional ART-loaded liposomes (IC50 3.13 nM). Furthermore, the assembled liposomes resulted in enhanced parasites killing in P. berghei-infected mice in vivo with delayed recrudescence and improved survivability, compared to free ART administration. Based on these encouraging results, Di-ART-GPC liposomal formulation could be a replacement to parent ART in clinical malarial therapy after thorough investigation.

Development of hyperbranched crosslinkers from bio-derived platform molecules for the synthesis of epoxidised soybean oil based thermosets.

Bio-based carboxyl-terminated hyperbranched crosslinkers have been synthesised by the facile esterification reaction of glycerol with succinic anhydride (Gly-SA). The Gly-SA crosslinking molecules have a large number of terminal carboxyl groups, which can crosslink through the epoxide of epoxidised soybean oil (ESO), making a highly flexible transparent film with excellent oxidative resistance. The effect of different molecular weights of Gly-SA cured ESO on the thermal and mechanical properties of the resulting films was also investigated. This study demonstrated that an increase in the molecular weights of Gly-SA, led to a decrease in the curing rate of mixtures, whilst the glass transition temperature (Tg) of Gly-SA cured ESO increased due to the incorporation of the bulky crosslinker. The use of a Gly-SA crosslinker prepared at 150 °C, resulted in a film (EGS150) with a tensile strength 13 times greater than of the control film, exhibited more than a 220% increase in elongation at break and the Young's modulus quadrupled compared to the value obtained for the control sample. It is noteworthy that the tensile strength and elongation at break improved with increasing Gly-SA chain length, suggesting the pre-polymerised crosslinkers contribute to the enhanced mechanical properties of the materials.

Liposomes assembled from dimeric retinoic acid phospholipid with improved pharmacokinetic properties

All-trans-retinoic acid (ATRA) exhibits potent cytotoxicities against different cancer cells by binding to retinoic acid receptors (RARs), which is regarded as the first example of targeted therapy in acute promyelocytic leukemia (APL). However, its extensive clinical applications have been limited because of poor aqueous solubility, short half-life time and side effects. In this report, dimeric ATRA phosphorylcholine prodrug (Di-ATRA-PC) was designed and assembled into nanoliposomes to improve its pharmacokinetic properties. Di-ATRA-PC prodrug was synthesized by a facile esterification and characterized by mass spectrometry (MS) and nuclear magnetic resonance spectroscopy (NMR). The Di-ATRA-PC assembled liposomes were prepared by thin film hydration method with ATRA loading efficiency up to 73wt%. The liposomes have a uniform particle size (73.1±3.6nm) with negatively charged surface (−20.5±2.5mV) and typical lipid bilayer structure as measured by dynamic light scattering (DLS), transmission electron microscope (TEM) and cryogenic transmission electron microscope (cryo-TEM). In vitro drug release study confirmed that Di-ATRA-PC liposomes could sustainedly release free ATRA in a weakly acidic condition. Furthermore, cellular uptake, MTT and cell apoptosis analysis demonstrated that the liposomes could be successfully internalized into tumor cells to induce apoptosis of MCF-7 and HL-60 cells. More importantly, in vivo pharmacokinetic assay indicated that Di-ATRA-PC liposomes had much longer retention time in comparison with ATRA. In conclusion, Di-ATRA-PC liposomal formulation could be a potential drug delivery system of ATRA with enhanced pharmacokinetic properties.

Magnetically recoverable AlFe/Te nanocomposite as a new catalyst for the facile esterification reaction under neat conditions

In this work, a new Fe3O4/AlFe/Te nanocomposite was synthesized by a one‐step sol–gel method. The Fe3O4 magnetic nanoparticles (MNPs) were prepared and then mixed with aluminum telluride (Al2Te3) in an alkali medium to produce the desired catalyst. After characterization of the Fe3O4/AlFe/Te nanocomposite by SEM, TEM, EDS, XRD, and ICP analyses, it was used in the esterification reaction. This heterogeneous catalyst showed high catalytic activity in the esterification of commercially available carboxylic acids with various alcohols to produce the desired esters at high conversions under neat conditions. The Fe3O4/AlFe/Te nanocomposites were separated from the reaction mixture via an external magnet and re‐used 8 times without significant loss of catalytic activity.

Green and Facile Esterification Procedure Leading to Crystalline-Functionalized Graphite Oxide.

A simple and eco-friendly procedure of esterification of graphite oxide (GO), which uses acetic anhydride as a model reagent and ethyl acetate as a green solvent, is reported. The procedure leads to high functionalization degrees (at least up to 4.5 mol % of acetyl groups, referred to as graphitic C atoms) and it is much more effective than the literature method based on pure acetic anhydride. Surprisingly, our acetylation procedure does not destroy or reduce GO crystallinity but, irrespective of a substantial increase of distance between GO layers (from 0.84 nm up to 0.95 nm), leads to an increased order in the direction perpendicular to the graphitic planes. This phenomenon indicates that acetyl groups of acetylated GO (AcGO) are easily accommodated between graphitic layers, even improving interlayer order. The esterification procedure is generally applicable with various anhydrides providing differently functionalized graphite oxide. Dispersion of crystalline functionalized GO in volatile organic solvents followed by solvent fast removal, can easily lead to complete exfoliation.