Phenolic Bond Research Articles

Late-Stage Radical C-H Alkylamination of Tyrosine Compounds and Phenol-Containing Drugs.

A modular site-selective iron-catalyzed radical amination of a number of phenol-containing biomolecules such as tyrosine-containing peptides, estrogens, and other phenol-based pharmaceuticals has been developed. The method features the use of the cost-efficient combination of FeBr3 as catalyst along with triflic acid as Brønsted acid, thereby enabling the predictable appendance of morpholine and related heterocycles at the ortho C-H bond of phenols in a late-stage fashion.

Influence of Additives on Grinding Performance of Digital Light Processing-Printed Phenol Bond Grinding Wheels

Resin bond grinding wheels are the most common grinding tools in the industry. Until now, all research on the additive manufacturing of resin bond grinding wheels has focused on commercially available acrylate resin. However, using a phenol-based bond to print resin-bond grinding wheels has been challenging for researchers and industries. In this study, a photo-curable phenol resin bond grinding wheel was introduced for the first time, offering advantages such as lower cost, high thermal resistance, and good mechanical properties. To enhance the grinding performance of the printed wheels, various additives, such as copper, glass fiber, and carbon fiber, were incorporated into the composition. Different on-machine and out-of-machine measurements, such as force, tool wear, dimensional accuracy, and optical microscopy measurements, were conducted to investigate the grinding performance of the printed wheels. The results demonstrate that printed grinding wheels have strong potential in grinding applications, which was more prominent for the bond reinforced by glass fibers, providing improved mechanical properties (up to 50%), wear resistance (up to 75%), and higher dimensional accuracy (up to 11%).

Potential of caffeic acid as an effective natural antioxidant for polypropylene-polyethylene copolymers: A DFT and experimental study

Caffeic acid (CAF) i is a polyphenolic compound commonly found in plants, valued for its ability to act as an antioxidant. This study focused on investigating the impact of a natural antioxidant, specifically caffeic acid (CAF), compared to two synthetic antioxidants, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT), on the thermal stability of propylene/ethylene copolymer (C-PP/PE), Aiming to establish a theoretical framework for the advancement of novel polymeric antioxidant compounds. Theoretical calculations were conducted to determine each compound's thermodynamic properties and antioxidant activity. The phenolic hydroxyl bond dissociation enthalpy (BDE) values revealed that BHA had the lowest value (325.6 kJ mol−1), trailed by CAF (328.2 kJ mol−1) and BHT (341.3 kJ mol−1), indicating a higher electron-donating capacity of BHA. Transition energy (TS) calculations indicated that BHA had the lowest TS energy (49.29 kJ mol−1), succeeded by CAF (57.61 kJ mol−1) and then BHT (75.57 kJ mol−1), suggesting greater efficiency in radical scavenging. Additionally, the obtained rate constants showed that CAF had the highest hydrogen abstraction rate (k = 1.05 × 10⁵ M⁻1 s⁻1), followed by BHA (k = 1.17 × 10⁴ M⁻1 s⁻1), and then BHT (k = 4.2 × 10³ M⁻1 s⁻1). These results support the effectiveness of CAF as a potentially more active antioxidant. In the experimental part of this study, it was observed that C-PP/PE with BHA showed a lower melt flow index (MFI) (8.51), indicating more excellent thermal stability. On the other hand, samples containing natural caffeic acid extracts exhibited a gradual decrease in MFI with increasing CAF concentration (MFI of 9.4, 8.82, 7.59, 6.44, and 5.98 for concentrations of 0.025, 0.05, 0.075, 0.1, and 0.125 ppm, respectively), suggesting a progressive improvement in the thermal stability of C-PP/PE with increasing natural antioxidant. In TGA analyses, decomposition was observed around 340 °C in samples without additives and those containing 0.1 ppm of BHA. In contrast, samples with different concentrations of CAF showed delayed degradation, observed in the temperature range of 380–400 °C. This delay in degradation indicates that CAF imparts more excellent thermal stability to C-PP/PE copolymer, as it reaches temperatures above 400 °C before starting its decomposition. These findings support the feasibility of using natural antioxidants such as CAF to improve the thermal properties of copolymers.

Ex-situ catalytic fast pyrolysis of waste polycarbonate for aromatic hydrocarbons: Utilizing HZSM-5/modified HZSM-5

Catalytic pyrolysis has been proven as a highly efficient process for transforming waste polycarbonate (PC) into valuable aromatic hydrocarbons, especially benzene, toluene, ethylbenzene, and xylene (BTEX). In the present work, the ex-situ catalytic fast pyrolysis of PC on metal- or alkali-modified HZSM-5 was investigated using the double micro-fixed bed system. Experimental results indicate that the rapid pyrolysis of PC may follow a homolytic chain scission mechanism, resulting in pyrolysis products dominated by phenols. Metal- or alkali-modified HZSM-5 significantly enhances the cleavage of C-OH bonds in phenols, improving the yield of aromatics. The yield of aromatics in the liquid product is 91 %, 72 %, and 77 % when loaded with nickel (Ni), iron (Fe), and cobalt (Co), respectively, all of which are higher than unmodified HZSM-5 with the yield of 43 %. Among them, the Ni/HZSM-5 has significantly enhanced the yield of BTEX reaching 81.64 %. When using alkali-modified HZSM-5 with a larger pore volume and higher specific surface area, the yield of aromatics can be increased to 60 %. Furthermore, the dual modification of alkali treatment and Ni loading on HZSM-5 simultaneously enhanced catalytic activity and resistance to coke formation. The yield of BTEX reaches 94.47 %. The BTEX formation mechanism can be explained by direct deoxygenation (DDO) of the pyrolytic volatiles of PC and the “phenol pool” mechanisms of primary products on the catalyst surface. This study enriches the understanding of catalytic pyrolysis of PC and provides a theoretical foundation for the harmless treatment of PC.

Mechanistic Insights into the Direct Deoxygenation of Phenolic Compounds over Novel Heusler Alloy Catalysts.

The catalytic deoxygenation of phenolic compounds is a crucial step in the valorization of biomass resources, which can effectively enhance the heating value and stability of primary biofuel. In this study, the catalytic mechanism of four Heusler alloy catalysts for the direct deoxidation pathway of phenol was studied through electronic structure regulation by element occupation. We found that Heusler alloys catalysts exhibit excellent catalytic activity in the dissociation activation of H2 and the cleavage of aryl hydroxyl bond (CAr-OH) bonds. The energy barriers for the direct cleavage of the CAr-OH bond in phenol on Ni2MoAl, Co2MoAl, Ni2NbAl and Ni2MoGa catalysts are 0.86, 0.95, 1.09, and 1.28 eV, respectively. And Y element of the X2YZ catalyst has a significant impact on this reaction, while the X element has a complex influence on the hydrogenation step of the unsaturated benzene ring. Microkinetic analysis further substantiates that the phenol (CAr-OH) bond cleavage step in the reaction exhibits a fast reaction rate and high extent of reaction. The reaction of hydroxyl hydrogenation to produce water exhibits the highest energy barrier, serving as the rate-determining step of the entire reaction. This issue could potentially be addressed by further fine-tuning the electronic structure.

Ultrafast Hot Exciton Nonadiabatic Excited-State Dynamics in Green Fluorescent Protein Chromophore Analogue.

The ultrafast high-energy nonadiabatic excited-state dynamics of the benzylidenedimethylimidazolinone chromophore dimer has been investigated using an electronic structure method coupled with on-the-fly quantitative wave function analysis to gain insight into the photophysics of hot excitons in biological systems. The dynamical simulation provides a rationalization of the behavior of the exciton in a dimer after the photoabsorption of light to higher-energy states. The results suggest that hot exciton localization within the manifold of excited states is caused by the hindrance of torsional rotation due to imidazolinone (I) or phenolate (P) bonds i.e., ΦI- or ΦP-dihedral rotation, in the monomeric units of a dimer. This hindrance arises due to weak π-π stacking interaction in the dimer, resulting in an energetically uphill excited-state barrier for ΦI- and ΦP-twisted rotation, impeding the isomerization process in the chromophore. Thus, this study highlights the potential impact of the weak π-π interaction in regulating the photodynamics of the green fluorescent protein chromophore derivatives.

Advances in the Synthesis of Poly(Phenolic Ester)s via Ring‐Opening Polymerization

AbstractThe poly(phenolic ester)s are attracting growing attention due to their essential role in the application as biodegradable plastics. Thus, extensive efforts have been devoted to the development of methodology that allows facile preparation of poly(phenolic ester)s with controlled molecular weights for widespread utilities. However, it is highly challenging to introduce phenolic ester bond structure into polyesters from ring‐opening polymerization (ROP) to yield aromatic/semiaromatic poly(phenolic ester)s due to severe transesterification reactions. To synthesize poly(phenolic ester)s with desired structures and properties, scientists have developed various ring‐opening polymerization systems with distinct advantages. Here, we have summarized basic features and recent progresses of these methods, including the cyclic phenolic lactone polymerization system, the salicylic acid O‐carboxyanhydride polymerization system, and the dissymmetric cyclic phenolic lactide polymerization system, as well as other copolymerization routes. Furthermore, the advantages and unsettled problems in various synthetic ways are discussed for readers to choose fast and controllable ROP systems for poly(phenolic ester)s.

Comparing industrial and analytical kraft lignins as biobased UV-protective additives in coatings

Lignin as the second most abundant biopolymer on Earth has the potential to become the alternative to petroleum-derived materials. It exhibits excellent UV absorption ability due to its aromatic structure and the presence of numerous phenolic, ketone, and intramolecular hydrogen bonds. Due to its complex nature, it is important to investigate its properties which is a very important step towards the valorization of lignin. Revealing its structural complexity allows for a better examination of its influence on the properties of the final lignin-based materials. In our research, we used two different kraft lignins: commercial analytical kraft lignin (AL) and industrial LignoBoost kraft lignin (KL) as UV-protect additives in BPA(Bisphenol A)-free polymer coatings based on diurethane dimethacrylate (DIUR). The maximum addition of KL and AL was 2 wt%. Both lignin samples were characterized in detail (composition analysis, ash content, molar mass and polydispersity, surface morphology, thermal properties, and quantitative measurement of hydroxyl group content). We investigated the influence of lignins on the textural and thermal properties of the coatings. Finally, we studied the application of lignin as a value-added UV-protective component by UV-Vis electronic absorption spectroscopy. KL with a higher purity and lower number of aliphatic OH had a better dispersion in the polymer matrix than AL lignin which had more agglomeration in the polymer matrix. The better dispersion resulted in producing a smoother surface in the coatings made from KL. Finally, a noticeable and significant impact of KL additive on the photoprotective properties of the coating material was demonstrated. These results showed a potential application and opportunity in the valorization of available industrial lignins toward sustainable and value-added products.

Role of tea polyphenols in enhancing the performance, sustainability, and catalytic cleaning capability of membrane separation for water-soluble pollutant removal

Tea polyphenols (TPs), like green tea polyphenol (GTP) and black tea polyphenol (BTP), with phenolic hydroxyl structures, form coordination and hydrogen bonds, making them effective for bridging inorganic catalysts and membranes. Here, TPs were employed as interface agents for the preparation of TPs-modified needle-clustered NiCo-layered double hydroxide/graphene oxide membranes (NiCo-LDH-TPs/GO). The incorporation of porous guest material, NiCo-LDH-TPs, facilitated water channel expansion, enhancing membrane permeability and resulting in the development of high-performance, sustainable catalytic cleaning membranes. The introduction of TPs through coordination weakened the surface electronegativity of NiCo-LDH, promoting a uniform mixed dispersion with GO and facilitating membrane self-assembly. NiCo-LDH-GTP/GO-5 and NiCo-LDH-BTP/GO-5 membranes demonstrated permeances of 85.98 and 90.76 L m−2 h−1 bar−1, respectively, with rejections of 98.73% and 99.54% for methylene blue (MB). Notably, the NiCo-LDH-BTP/GO-5 membrane maintained a high rejection of 97.11% even after 18 cycles in the catalytic cleaning process. Furthermore, the modification of GTP and BTP enhanced MB degradation through PMS activation, resulting in a 0.33% and 0.35% increase in the reaction rate constants of NiCo-LDH, respectively, while reducing metal ion spillover. These findings highlighted the potential of TPs in enhancing the efficiency and sustainability of catalytic cleaning GO membranes for water purification and separation processes.

Modelling the fragmentation kinetics of the heterogeneous lignin macromolecule during kraft pulping with stochastic graphs

This article presents a novel concept for modelling the kinetics and related phenomena of the kraft pulping process on a macromolecule level with the initial objective to explicitly model and relate the breakage of phenolic and non-phenolic βO4 bonds to the observed three-stage delignification profile. The modelling frameworks consist of the building and the fragmentation of the lignin macromolecules. The macromolecules are modelled as stochastic graphs where monolignol object nodes are reassembled in a Monte Carlo approach into internal structures, which aggregate to a lignin macromolecule interconnected through chemical bonds represented by the edges of the graphs. The fractionation follows the splitting of βO4 ether bonds with different configurations resulting from functional groups attached to the monolignols, namely the phenolic and non-phenolic βO4 bonds with their respective stereochemistry. It is tested against a previously published model based on an extension of the established Purdue kinetic model and experimental data. The results align with the observed delignification trajectory during kraft pulping, and the hypothesis that βO4 bonds splitting is mainly responsible for the delignification. However, some discrepancies between the current model, the previous model and experimental data are presented. These differences are discussed in the context of recent experimental findings indicating that βO4 bonds splitting might not entirely be responsible for the delignification due to mass transfer/solubility effects limitations.

Tetrabutylammonium Halides as Selectively Bifunctional Catalysts Enabling the Syntheses of Recyclable High Molecular Weight Salicylic Acid‐Based Copolyesters

AbstractTo synthesize high molecular weight poly(phenolic ester) via a living ring‐opening polymerization (ROP) of cyclic phenolic ester monomers remains a critical challenge due to serious transesterification and back‐biting reactions. Both phenolic ester bonds in monomer and polymer chains are highly active, and it is difficult so far to distinguish them. In this work, an unprecedented selectively bifunctional catalytic system of tetra‐n‐butylammonium chloride (TBACl) was discovered to mediate the syntheses of high molecular weight salicylic acid‐based copolyesters via a living ROP of salicylate cyclic esters (for poly(salicylic methyl glycolide) (PSMG), Mn=361.8 kg/mol, Ð<1.30). Compared to previous catalysis systems, the side reactions were suppressed remarkably in this catalysis system because phenolic ester bond in monomer can be selectively cleaved over that in polymer chains during ROP progress. Mechanistic studies reveal that the halide anion and alkyl‐quaternaryammonium cation work synergistically, where the alkyl‐quaternaryammonium cation moiety interacts with the carbonyl group of substrates via non‐classical hydrogen bonding. Moreover, these salicylic acid‐based copolyesters can be recycled to dimeric monomer under solution condition, and can be recycled to original monomeric monomers without catalyst under sublimation condition.

Tetrabutylammonium Halides as Selectively Bifunctional Catalysts Enabling the Syntheses of Recyclable High Molecular Weight Salicylic Acid-Based Copolyesters.

To synthesize high molecular weight poly(phenolic ester) via a living ring-opening polymerization (ROP) of cyclic phenolic ester monomers remains a critical challenge due to serious transesterification and back-biting reactions. Both phenolic ester bonds in monomer and polymer chains are highly active, and it is difficult so far to distinguish them. In this work, an unprecedented selectively bifunctional catalytic system of tetra-n-butylammonium chloride (TBACl) was discovered to mediate the syntheses of high molecular weight salicylic acid-based copolyesters via a living ROP of salicylate cyclic esters (for poly(salicylic methyl glycolide) (PSMG), Mn =361.8 kg/mol, Ð<1.30). Compared to previous catalysis systems, the side reactions were suppressed remarkably in this catalysis system because phenolic ester bond in monomer can be selectively cleaved over that in polymer chains during ROP progress. Mechanistic studies reveal that the halide anion and alkyl-quaternaryammonium cation work synergistically, where the alkyl-quaternaryammonium cation moiety interacts with the carbonyl group of substrates via non-classical hydrogen bonding. Moreover, these salicylic acid-based copolyesters can be recycled to dimeric monomer under solution condition, and can be recycled to original monomeric monomers without catalyst under sublimation condition.

Preparation and Molecular Structural Characterization of Fulvic Acid Extracted from Different Types of Peat.

Humic acid is a type of polymeric, organic weak acid mixture with a core aromatic structure and main-component oxygen-containing functional group. Fulvic acid is a type of humic substance that can be dissolved in acid, alkali, or water. This study discusses the influence of different peptides on the molecular structure of fulvic acid, which was extracted from herbaceous, woody, and mossy peats using alkaline dissolution and acid precipitation methods. Analyses using infrared, UV-Vis, 13C-NMR, and X-ray photoelectron spectroscopies, as well as X-ray diffraction (XRD), were conducted to compare the effects of different peat types on the content and molecular structure of fulvic acid. The woody peat fulvic acid content was the highest among all peat fulvic acids (0.38%). However, the yield of fulvic acid from herbaceous peat was the highest (2.53%). Herbaceous peat fulvic acid contains significant quantities of carbonyl, amino, methylene, carboxyl, and phenolic hydroxyl groups and ether bonds. Woody peat fulvic acid contains carbonyl and methoxy groups, benzenes, aromatic carbons, aromatic ethers, and phenols. The degree of aromatization of woody peat fulvic acid was the highest. Mossy peat fulvic acid contains high levels of hydroxy, methyl, methylene, and phenol groups and aromatic ethers. The structural differences in fulvic acids in the different types of peat were primarily manifested in the content of functional groups, with little influence from the types of functional groups. XRD analysis of the different peats revealed that their structures all comprised benzene rings. However, mossy peat contained more C=O and -COOH groups, whereas herbaceous peat contained more C-O groups.

Spontaneous Generation of Aryl Carbocations from Phenols in Aqueous Microdroplets: Aromatic SN1 Reactions at the Air-Water Interface.

Although phenol is stable in bulk water, we report an exceptional phenomenon in which phenol is spontaneously transformed into a phenyl carbocation (Ph+) in water microdroplets. The high electric field at the air-water interface is proposed to break the phenolic Csp2-OH bond, forming Ph+, which remains in equilibrium with phenol as deciphered by mass spectrometry. We detected up to 70% conversion of phenol to Ph+ in aqueous microdroplets, although catalyst-free activation of the phenolic Csp2-OH bond is challenging. This transformation is well tolerated by a wide range of electron-donating and -withdrawing substituents in phenolic compounds. The Ph+ in water microdroplets could be reacted with various nucleophiles (amine, pyridine, azide, thiol, carboxylic acid, alcohol, and 18O-water), yielding the ipso-substitution products of phenol through an aromatic SN1 mechanism. Despite the fleeting life of Ph+ in the bulk, this study demonstrates its unusual stability at the aqueous microdroplet surface, enabling its detection and transformation.

Cleavage of macromolecule (protein/polysaccharide)-phenolic bond in soybean cell wall through Lactobacillus casei and Lactobacillus helviticus mixed culture solid-state fermentation for chlorogenic acid extraction

Out of the available dietary sources use for chlorogenic acid extraction, soybean is new and cheap that could offer cost-effective chlorogenic acid production under solid-state fermentation (SSF). Consequently, the study aimed at investigating the cleavage of protein/carbohydrate-phenolic bond in heilong48 soybean (HS) variety via solid-state fermentation by Lactobacillus casei and Lactobacillus helviticus mixed culture for chlorogenic acid extraction with high yield and increased biological activity. A simplistic two-pot bioproduct optimization approach was used; first, screening (Plackett-Burman design) of SSF conditions and second, optimizing (Box-Behnken design) the significant SSF conditions obtained from the former design. The liquid-solid (liquid:solid) ratio of 32:68 (0.47), incubation time of 48 h, pH of 5, and temperature of 50 °C were the best-optimized SSF conditions obtained from the chronological combinatory screening and optimization methods. These conditions gave a satisfactory SSF model, and correspondingly acceptable chlorogenic acid yield (9.20 ± 0.17 mg/g), fermentation efficiency (37.26 ± 0.73%), and 2,2-diphenyl-1-picrylhydrazyl free radical-scavenging activity (DPPH) (65.21 ± 2.05 μmol AA eq/g dry sample) results. The L. casei and L. helviticus mixed culture fermented heilong48 soybean (MCFHS) sample (under optimized SSF conditions) had high (p < 0.05) chlorogenic acid yield and 2,2-diphenyl-1-picrylhydrazyl free radical-scavenging activity than the raw heilong48 soybean flour (RHSF) sample. The effectiveness of the optimized solid-state fermentation conditions on the structural modifications of heilong48 soybean sample was confirmed by scanning electron microscopy, atomic force microscopy, and Fourier transform infrared results.

Recent Advances in Regioselective C-H Bond Functionalization of Free Phenols.

Phenols are important readily available synthetic building blocks and starting materials for organic synthetic transformations, which are widely found in agrochemicals, pharmaceuticals, and functional materials. The C-H functionalization of free phenols has proven to be an extremely useful tool in organic synthesis, which provides efficient increases in phenol molecular complexity. Therefore, approaches to functionalizing existing C-H bonds of free phenols have continuously attracted the attention of organic chemists. In this review, we summarize the current knowledge and recent advances in ortho-, meta-, and para-selective C-H functionalization of free phenols in the last five years.

Mechanistic insight into the free radical scavenging and xanthine oxidase (XO) inhibitor potent of monoacetylphloroglucinols (MAPGs)

Three novel antioxidant candidates based on phenolic polyketide, monoacetylphloroglucinol (MAPG), a natural antibiotic compound produced by plant growth-promoting rhizobacteria (PGPR), Pseudomonas fluorescens F113 have been proposed. Initially, a green and highly efficient route to the synthesis of MAPG and its two analogues from phloroglucinol (PG) has been developed. Afterward, their rational mechanism of antioxidant activity has been investigated based on thermodynamic descriptors involved in the double (/) radical trapping processes. These calculations have been performed using the systematic density functional theory (DFT) method at the B3LYP/Def2-SVP level of theory in the gas phase and aqueous solution. Our findings reveal that the double formal hydrogen atom transfer (df-HAT) mechanism is preferred in the gas phase, while the double sequential proton loss electron transfer (dSPLET) mechanism is preferred in aqueous solution for all MAPGs. The 6–OH group represents the most favorable site for trapping radical species for all MAPGs, which is supported by the pKa values obtained from DFT calculations. The role of acyl substituents on the PG ring has been comprehensively discussed. The presence of acyl substituents has a strong influence on the thermodynamic parameters of the phenolic O–H bond in PG. These results are supported by frontier molecular orbitals (FMOs) analysis, where the addition of acyl substituents increases the chemical reactivity of MAPGs significantly. Based on molecular docking and molecular dynamic simulations (MDs), MAPGs are also predicted to be promising candidates for xanthine oxidase (XO) inhibition. Highlights The antioxidant activity of the three synthesized monoacetylphloroglucinols (MAPGs) has been investigated using the density functional theory (DFT) method. Acyl substituents increase the chemical reactivity and antioxidant activity of MAPGs. Double formal hydrogen atom transfer (df-HAT) is the preferred mechanism in the gas phase. Double sequential proton loss electron transfer (dSPLET) seems to be more favored in aqueous solution. MAPGs are expected to be promising xanthine oxidase (XO) inhibitors.

Revealing adsorption of mixed enzymes onto lignin resulted from integration of hydrothermal and chemi-mechanical pretreatment

Lignin is the main factor inhibiting enzymatic hydrolysis of lignocellulosic biomass. Different pretreatments can alter chemical and structural characteristics of lignin, thus affecting its adsorption capacity of enzymes. Herein, enzymatic mild acid lignin (EMAL) was separated from poplar branch wood chips as substrates resulted from different combined pretreatments, and then characterized and adsorbed by enzymes, so as to study the effects of different pretreatments on enzyme adsorption capacity. The results showed that the phenolic hydroxyl content and CC bond number of lignin increased after hydrothermal pretreatment, which increased the unproductive adsorption of mixed enzymes through hydrophobic interaction and hydrogen bonds. Chemical pretreatment after hydrothermal pretreatment can further reduce the unproductive adsorption of lignin on mixed enzymes, improving the enzymatic hydrolysis of substrates. This study would help to unmask the adsorption of mixed enzymes on lignin resulted from combined pretreatments, and facilitate the rapid development of efficient pretreatment for lignocellulosic biomass.

Palladium-Catalyzed Chemo- and Regioselective C-H Bond Functionalization of Phenols with 1,3-Dienes.

Chemo- and site-selective functionalization of phenols offers a rapid strategy for the synthesis of phenol derivatives with diverse structures. Herein, we report a Pd-catalyzed regioselective C-H bond allylic alkylation of phenols with 1,3-dienes, which has precision reactivity at the ortho C-H bond of 2-naphthols, 1-naphthols, and electron-rich phenols. The reaction is accelerated by a diphosphine ligand, does not need any other additive, and features broad substrate scope and good chemo- and regioselectivity. In addition, we have also investigated the asymmetric variant, and the product could be achieved in up to 55% ee.

Esterase-Responsive Polymeric Micelles Containing Tetraphenylethene and Poly(ethylene glycol) Moieties for Efficient Doxorubicin Delivery and Tumor Therapy.

Enzyme-responsive drug delivery systems have drawn much attention in the field of cancer theranostics due to their high sensitivity and substrate specificity under mild conditions. In this study, an amphiphilic polymer T1 is reported, which contains a tetraphenylethene unit and a poly(ethylene glycol) chain linked by an esterase-responsive phenolic ester bond. In aqueous solution, T1 formed stable micelles via self-assembly, which showed an aggregation-induced emission enhancement of 32-fold at 532 nm and a critical micelle concentration of 0.53 μM as well as esterase-responsive activity. The hydrophobic drug doxorubicin (DOX) was efficiently encapsulated into the micelles with a drug loading of 21%. In the presence of the esterase, the selective decomposition of drug-loaded T1 micelles was observed, and DOX was subsequently released with a half-life of 5 h. In vitro antitumor studies showed that T1@DOX micelles exhibited good therapeutic effects on HeLa cells, while normal cells remained mostly intact. In vivo anticancer experiments revealed that T1@DOX micelles indeed suppressed tumor growth and had reduced side effects compared to DOX·HCl. The present work showed the potential clinical application of esterase-responsive drug delivery in cancer therapy.