Diels-Alder Research Articles

A self‐healing polymer electrolyte based on the Diels–Alder reaction in lithium‐ion batteries

AbstractIn lithium‐ion batteries, the polymer electrolyte was susceptible to mechanical damage from external stimuli or internal expansion caused, which in turn affected the performances of the batteries. The thermally reversible self‐healing gel polymer electrolyte (DASHPE) based on the Diels–Alder reaction was prepared to solve the above problems. The DASHPE electrolytes exhibited good flexibility and self‐healing ability, achieving self‐healing at 80°C for 30 min. Furthermore, the DASHPE electrolyte exhibited excellent thermal stability and could withstand temperatures above 300°C. Additionally, it had a wide electrochemical window (about 5 V) and good electrochemical performances. Serving as the electrolyte in lithium‐ion batteries, DASHPE‐2 showed an initial specific capacity of 133.11 mAh g−1 at 0.1 C. The DASHPE electrolyte was expected to be a candidate material for self‐healing battery.

Triazine-containing porous organic polymers from Diels-Alder reactions for efficient molecular adsorption and photocatalytic degradation

As a reversible and simple synthetic strategy, Diels-Alder (DA) reactions were recently exploited for the construction of porous organic polymers (POPs) with diverse structures and functions, which hold the promise to synthesize functional POPs in large scale. However, these methods typically need high polymerization temperature, and the structural diversity is limited for their practical applications. In this work, a series of DA-POPs were successfully synthesized via the Diels-Alder reactions of furan- and alkynyl-functionalized monomers. To reduce the activation energy of the reaction, we introduced 1,3,5-triazine moiety to alkynyl-functionalized monomers, which substantially lowered the polymerization temperature to 120 °C. Leveraging the reported photoelectric activity from triazine moiety, we applied these POPs materials to the adsorption and photocatalytic degradation of the organic dye Rhodamine B, exhibiting remarkable adsorption and degradation ability. Photophysical tests further elucidated the degradation mechanism and corroborated the photocatalytic application potential of these DA-POPs. This work brings a new synthetic strategy for the elaboration of POPs for reducing environmental pollution via photocatalytic waste degradation.

Kinetics of the Diels–Alder Reaction of Thiofluorenone with 9,10-Dimethylanthracene

Kinetics of the Diels–Alder Reaction of Thiofluorenone with 9,10-Dimethylanthracene

Asymmetric Total Synthesis of (+)-Verrubenzospirolactone and (+)-Capillobenzopyranol.

The first asymmetric total synthesis of (+)-verrubenzospirolactone (1), a distinctive highly fused benzosesquiterpenoid, characterized by a pentacyclic skeletal structure, is realized through a concise 10-step synthetic pathway with an impressive 22.8% overall yield. Notable highlights of this synthetic endeavor include (i) the introduction of a Ru-catalyzed ortho C-H activation step, (ii) the application of Pd-catalyzed asymmetric allylic alkylation to establish a pivotal stereocenter at C-3 with an excellent enantiomeric excess, (iii) B-alkyl Suzuki-Miyaura coupling to construct a Diels-Alder precursor, and, ultimately, (iv) the successful deployment of an intramolecular Diels-Alder reaction to complete the synthesis of (+)-verrubenzospirolactone without erosion of the enantiomeric excess.

Asymmetric Total Synthesis of (+)-Chuanxiongnolide L1 via a Stereoselective Oxidative Dearomatization/Diels-Alder Strategy.

The first asymmetric total synthesis of chuanxiongnolide L1 was achieved in 16 steps and 1.9% overall yield by employing a bioinspired chiral auxiliary strategy. The key steps involving asymmetric oxidative dearomatization of chiral amino ether and subsequent asymmetric Diels-Alder reaction of the resulting masked chiral ortho-benzoquinone were adopted.

Total Syntheses of Borolithochromes A, D and G.

Total syntheses of borolithochromes A, D and G, red pigments isolated from fossils of Jurassic putative red alga Solenopora jurassica, have been achieved. The benzo[gh]tetraphene skeletons of the borate ligands in these substances were constructed using Diels-Alder reactions of aryl dienes with naphthoquinone, followed by intramolecular Corey-Chaykovsky reactions. Complexation of these ligands with trimethyl borate generated homocomplexes, which upon sequential O-demethylation produced borolithochromes A and G. In the route to borolithochrome D, a heterocomplex was prepared by stepwise complexation of the ligands with 2-(dimethylamino)ethyl dimethyl borate. The strategy devised to accomplish the first total synthesis of borolithochromes A, D and G should be applicable to the preparation of other borolithochromes as well as spiroborates possessing two fused polycyclic aromatic ligands.

The variational quantum eigensolver self-consistent field method within a polarizable embedded framework.

We formulate and implement the Variational Quantum Eigensolver Self Consistent Field (VQE-SCF) algorithm in combination with polarizable embedding (PE), thereby extending PE to the regime of quantum computing. We test the resulting algorithm, PE-VQE-SCF, on quantum simulators and demonstrate that the computational stress on the quantum device is only slightly increased in terms of gate counts compared to regular VQE-SCF. On the other hand, no increase in shot noise was observed. We illustrate how PE-VQE-SCF may lead to the modeling of real chemical systems using a simulation of the reaction barrier of the Diels-Alder reaction between furan and ethene as an example.

A Neutral PCNHCP Co(I)-Me Pincer Complex as a Catalyst for N-Allylic Isomerization with a Broad Substrate Scope.

Earth-abundant-metal catalyzed double bond transposition offers a sustainable and atom-economical route toward the synthesis of internal alkenes. With an emphasis specifically on internal olefins and ethers, the isomerization of allylic amines has been particularly under represented in the literature. Herein, we report an efficient methodology for the selective isomerization of N-allylic organic compounds, including amines, amides, and imines. The reaction is catalyzed by a neutral PCNHCP cobalt(I) pincer complex and proceeds via a π-allyl mechanism. The isomerization occurs readily at 80-90 °C, and it is compatible with a wide variety of functional groups. The in situ formed enamines could additionally be used for a one-pot inverse-electron-demand Diels-Alder reaction to furnish a series of diversely substituted heterobiaryls, which is further discussed in this report.

Mechanistic insights into Ga-modified hollow ZSM-5 catalyzed fast pyrolysis of cassava residue

The preparation of valuable chemicals by catalytic fast pyrolysis (CFP) is a promising and environmentally-friendly approach for the selective upgrading of waste cassava residue (CR). This work systematically investigated the conversion mechanism and kinetic characteristics of CR pyrolysis over Ga-modified hollow ZSM-5, for the purpose of enhancing aromatics production. The hollow configuration significantly regulated the structural characteristics of ZSM-5, thus facilitating the diffusion, deoxygenation, and aromatization of pyrolysis intermediates. The incorporation of Ga species and generated Brønsted acid sites remarkably accelerated the reaction rate and suppressed the carbonization at high temperatures, through enhancing the end scission of starch and cellulose components. With the aid of 5Ga/ZSM-H, the relative content of aromatics achieved 95.4% at 700 °C, and still maintained over 92.5% even after 5 cycles. The ring-opening and retro-aldol degradation were identified as crucial steps for the production of ketones and aldehydes separately, which were further transformed into hydrocarbon pools by deoxygenation and subsequently converted into aromatics via Diels-Alder reaction. Kinetic analysis demonstrated that the use of 5Ga/ZSM-H lowered the average activation energy of CR pyrolysis by 14.8%, particularly for the initial pyrolysis stage. Moreover, the plausible mechanism for aromatics formation from Ga-modified hollow ZSM-5 catalyzed CR pyrolysis was proposed.

Selective Late-Stage Functionalization of Tryptophan-Containing Peptides To Facilitate Bioorthogonal Tetrazine Ligation.

Site-selective modification of complex peptides and the functionalization of their C-H bonds hold great promise for expanding their use in therapeutics and biomedical research. Herein, we leverage the power of late-stage chemoenzymatic catalysis using an indole prenyltransferase (IPT) enzyme and alkyl diphosphates to specifically modify the indole ring of tryptophan in clinically relevant peptides. Furthermore, the installed handle enables bioorthogonal click chemistry through an inverse electron-demand Diels-Alder (IEDDA) reaction with a biotin-conjugated tetrazine probe.

Electrospun photothermally active graphene-based nanofibers with a Retro-Diels-Alder reaction to initiate drug release

Externally controlled local drug release systems have garnered significant interest, with stimuli-responsive electrospun nanofibers emerging as a prominent platform for local drug delivery. Their advantages, such as a high surface area and facile production have made them appealing materials for various biomedical applications. While nanofiber scaffolds have been widely used for drug release through physical entrapment, control over the passive release and precise dosage regulation remains challenging. To overcome these limitations, in this study, maleimide-modified functional molecules were covalently conjugated to reduced graphene oxide-containing nanofiber scaffolds (average diameter 475 ± 94 nm) fabricated using furan-containing copolymers. The Diels-Alder cycloaddition at ambient temperature conjugates the molecules of interest, whereas the thermally promoted retro Diels-Alder cycloreversion reaction releases them. Photothermal heating using near-infrared light at 980 nm facilitated control over the drug release, and switching the irradiation on and off allows on-demand release. One can envision that these photothermally active nanofiber mats could enable on-demand drug delivery of a variety of active therapeutic agents for localized delivery.

Recent Advances in Polymer Nanocomposites: Unveiling the Frontier of Shape Memory and Self-Healing Properties-A Comprehensive Review.

Shape memory and self-healing polymer nanocomposites have attracted considerable attention due to their modifiable properties and promising applications. The incorporation of nanomaterials (polypyrrole, carboxyl methyl cellulose, carbon nanotubes, titania nanotubes, graphene, graphene oxide, mesoporous silica) into these polymers has significantly enhanced their performance, opening up new avenues for diverse applications. The self-healing capability in polymer nanocomposites depends on several factors, including heat, quadruple hydrogen bonding, π-π stacking, Diels-Alder reactions, and metal-ligand coordination, which collectively govern the interactions within the composite materials. Among possible interactions, only quadruple hydrogen bonding between composite constituents has been shown to be effective in facilitating self-healing at approximately room temperature. Conversely, thermo-responsive self-healing and shape memory polymer nanocomposites require elevated temperatures to initiate the healing and recovery processes. Thermo-responsive (TRSMPs), light-actuated, magnetically actuated, and Electrically actuated Shape Memory Polymer Nanocomposite are discussed. This paper provides a comprehensive overview of the different types of interactions involved in SMP and SHP nanocomposites and examines their behavior at both room temperature and elevated temperature conditions, along with their biomedical applications. Among many applications of SMPs, special attention has been given to biomedical (drug delivery, orthodontics, tissue engineering, orthopedics, endovascular surgery), aerospace (hinges, space deployable structures, morphing aircrafts), textile (breathable fabrics, reinforced fabrics, self-healing electromagnetic interference shielding fabrics), sensor, electrical (triboelectric nanogenerators, information energy storage devices), electronic, paint and self-healing coating, and construction material (polymer cement composites) applications.

Caged xanthone derivatives to promote mitochondria-mediated apoptosis in breast cancer cells

Caged xanthones represent a class of natural secondary metabolites exhibiting significant potential as antitumor agents. These compounds are characterized by their distinct cage-like structures, which offer novel and compelling frameworks for drug design. Nonetheless, there exists a dearth of research focused on the structural modification of these compounds, particularly in relation to their cage-like architectures. This study aims to address this gap by introducing an innovative synthetic method for constructing a novel caged structure that incorporates a widely employed maleimide group. Drawing upon the well-established synthetic approach for dihydroxanthones previously developed within our research group, we successfully synthesized 13 new caged xanthones using the Diels-Alder reaction. Subsequently, we evaluated their anti-proliferative activity against HepG2, A549, and MDA-MB-231 cell lines. The results revealed that compound 10i exhibited IC50 values of 15.86 µM ± 1.29, 19.27 µM ± 1.58, and 12.96 µM ± 0.09 against these cell lines, respectively. Further investigations into the mechanism of action of 10i demonstrated its ability to induce G2/M cell cycle arrest and initiate mitochondria-mediated apoptosis in breast cancer cells.

Construction of trifloaluminate ionic liquid catalyst on the silica surface dedicated for continuous flow Diels-Alder synthesis

Supported ionic liquid phases (SILP) are efficiently use for the construction of highly active, heterogeneous and recyclable catalysts. In this study, three strategies towards chemical immobilization of trifloaluminate ionic liquid catalyst into microporous/mesoporous silica support were investigated. The order of silica surface modification with trifloaluminate ILs components had crucial influence on the catalytic activity and stability which was tested in the model Diels-Alder reaction between isoprene and maleic anhydride in acetonitrile at room temperature. The best catalytic performance (maleic anhydride conversion > 97% in ten reaction cycles) was achieved for catalyst created through the synthesis of trifloaluminate ionic liquid in the first step with further bounding to the silica surface using 25 wt% of ionic liquid loading. The effective transformation of the Diels-Alder reaction to continuous flow synthesis led to 97% maleic anhydride conversion over 432 h with a TOF of 104.3 h−1 and significantly improved process sustainability.

Injectable and Multifunctional Hydrogels Based on Poly(N-acryloyl glycinamide) and Alginate Derivatives for Antitumor Drug Delivery.

Chemotherapy is a conventional treatment that uses drugs to kill cancer cells; however, it may induce side effects and may be incompletely effective, leading to the risk of tumor recurrence. To address this issue, we developed novel injectable thermal/near-infrared (NIR)-responsive hydrogels to control drug release. The injectable hydrogel formulation was composed of biocompatible alginates, poly(N-acryloyl glycinamide) (PNAGA) copolymers with an upper critical solution temperature, and NIR-responsive cross-linkers containing coumarin groups, which were gelated through bioorthogonal inverse electron demand Diels-Alder reactions. The hydrogels exhibited quick gelation times (120-800 s) and high drug loading efficiencies (>90%). The hydrogels demonstrated a higher percentage of drug release at 37 °C than that at 25 °C due to the enhanced swelling behavior of temperature-responsive PNAGA moieties. Upon NIR irradiation, the hydrogels released most of the entrapped doxorubicin (DOX) (97%) owing to the cleavage of NIR-sensitive coumarin ester groups. The hydrogels displayed biocompatibility with normal cells, while induced antitumor activity toward cancer cells. DOX/hydrogels treated with NIR light inhibited tumor growth in nude mice bearing tumors. In addition, the injected hydrogels emitted red fluorescence upon excitation at a green wavelength, so that the drug delivery and hydrogel degradation in vivo could be tracked in the xenograft model.

Endergonic synthesis driven by chemical fuelling

AbstractSpontaneous chemical reactions proceed energetically downhill to either a local or global minimum, limiting possible transformations to those that are exergonic. Endergonic reactions do not proceed spontaneously and require an input of energy. Light has been used to drive a number of deracemizations and thermodynamically unfavourable bond-forming reactions, but is restricted to substrates that can absorb, directly or indirectly, energy provided by photons. In contrast, anabolism involves energetically uphill transformations powered by chemical fuels. Here we report on the transduction of energy from an artificial chemical fuel to drive a thermodynamically unfavourable Diels–Alder reaction. Carboxylic acid catalysed carbodiimide-to-urea formation is chemically orthogonal to the reaction of the diene and dienophile, but transiently brings the functional groups into close proximity, causing the otherwise prohibited cycloaddition to proceed in modest yield (15% after two fuelling cycles) and with high levels of regio- (>99%) and stereoselectivity (92:8 exo:endo). Kinetic asymmetry in the fuelling cycle ratchets the Diels–Alder reaction away from the equilibrium distribution of the Diels–Alder:retro-Diels–Alder products. The driving of the endergonic reaction occurs through a ratchet mechanism (an energy or information ratchet, depending on the synthetic protocol), reminiscent of how molecular machines directionally bias motion. Ratcheting synthesis has the potential to expand the synthetic chemistry toolbox in terms of reactivity, complexity and control.

Responsive Microgels through RAFT-HDA Dynamic Covalent Bonding Chemistry.

This paper developed a method for preparing ultrasound-responsive microgels based on reversible addition fragmentation chain transfer-hetero Diels-Alder (RAFT-HAD) dynamic covalent bonding. First, a styrene cross-linked network was successfully prepared by a Diels-Alder (DA) reaction between phosphoryl dithioester and furan using double-ended diethoxyphosphoryl dithiocarbonate (BDEPDF) for RAFT reagent-mediated styrene (St) polymerization, with a double-ended dienophile linker and copolymer of furfuryl methacrylate (FMA) and St as the dienophile. Subsequently, the microgel system was constructed by the HDA reaction between phosphoryl disulfide and furan groups using the copolymer of polyethylene glycol monomethyl ether acrylate (OEGMA) and FMA as the dienophore building block and hydrophilic segment and the polystyrene pro-dienophile linker as the cross-linker and hydrophobic segment. The number of furans in the dienophile chain and the length of the dienophile linker were regulated by RAFT polymerization to investigate the effects of the single-molecule chain functional group degree, furan/dithioester ratio, and hydrophobic cross-linker length on the microgel system. The prepared microgels can achieve the reversible transformation of materials under force responsiveness, and their preparation steps are simple and adaptive to various potential applications in biomedical materials and adaptive electrical materials.

Asymmetric Diels–Alder reaction of chalcone and isoprene mediated by titanium-based complexes

The asymmetric Diels–Alder reaction of chalcone and isoprene has been accomplished by use of chiral titanium complexes. Notably, an enantiomeric excess as high as 61% and a regioselectivity of 95% have been achieved. The preparation of the chiral titanium complexes is simple and does not require the pre-installation of a chiral auxiliary. This study represents the first example of asymmetric Diels–Alder reaction between chalcone and isoprene.

On the reactivity and selectivity trends in the tandem Diels-Alder cycloaddition and dehydrative aromatization between dimethylfuran and ethene over solid acids

Tandem Diels-Alder (DA) cycloaddition and dehydration reactions between bio-derived furans and dienophiles offer a sustainable route potentially able to meet the growing demands of aromatic chemicals worldwide. In particular, efforts to maximize the production of p-xylene from dimethylfuran (DMF) and ethene have led to an expanding list of solid acids with, reportedly, outstanding catalytic performances. In this work, we have revisited the kinetic complexities of this reaction that are characterized by a distinct shift in the rate-limiting step depending sensitively on catalyst mass, and addressed the possible origins of reactivity and selectivity trends across a range of solid acids that hold promise for the target reaction, including aluminosilicates and a series of mesoporous metal phosphate catalysts (MOPOx; M = Sn, Ti, Zr, Hf, Nb and Ta), in both dehydration- and cycloaddition-limiting regimes. In contrast to initial p-xylene formation rates in the dehydration-limiting regime, which benefit from an increased acid strength of Brønsted acid sites, p-xylene formation rates within the cycloaddition-limiting regime are essentially unaffected by variations in acid site densities, Lewis and Brønsted acid strength, and pore confinement. Such weak dependences of DA reactivity on a multitude of acid properties provide strong hints that DA cycloaddition between DMF and ethene follows an inverse-electron-demand [4 + 2] route, most likely as a consequence of a more favorable adsorption of DMF than that of ethene on the acid sites enhancing so the electrophilicity of DMF, but not that of ethene as required by the normal-electron-demand cycloaddition. Product selectivities and carbon balances were tracked as functions of reaction time, conversion and reactant pressure or concentration to identify the side reactions and acid properties responsible for p-xylene selectivity losses and the ultimate formation of carbonaceous deposits. These findings deepen our understanding of the roles of Lewis acid sites and Brønsted acid sites for the chemical reactivities toward the DA cycloaddition, the consecutive cycloadduct dehydrative aromatization and undesired acid-catalyzed side reactions, and inform strategies to enhance DA reactivities and suppress deleterious side reactions from the standpoint of both materials and process design.

Click-imprinted furan-modified poly(acrylonitrile-co-divinylbenzene for S-naproxen recognition

Naproxen (NX) drug exists in two R- and S-enantiomers, requiring enantioseparation for effective pharmacological effects. Herein, a new S-NX enantioselective poly(acrylonitrile-co-divinylbenzene) (CPAN)-based polymeric sorbent was successfully synthesized and used to separate the NX racemate. First, low crosslinked CPAN was prepared in microparticles via suspension polymerization. Furan-2-ylmethylhydrazine (Fu-Hyd) was then interacted with the abundant nitrile units. The resulting cationic furan-hydrazidine-functionalized polymeric particles (FUH-P) were loaded with the anionic S-NX, which was then imprinted via post-crosslinking upon treatment with bis-maleimidoethane (BME) dienophile crosslinker that interacted with the conjugate diene system of the already inserted furan units via Diels-Alder cycloaddition reaction. Using acidic elution, the S-NX enantiomers were then freed from the polymer particle and left their enantio-selective receptor-like active sites in the structure of the imprinted polymeric particles (S-NX-P). FTIR, 13C NMR, and XRD techniques were utilized for investigating the obtained polymers. Also, the surface morphologies of the sorbent materials were visualized using SEM. The best conditions for enantio-selective uptake showed that 235 mg/g of S-NX could be adsorbed at pH 7. The enantiomeric separation of the NX racemic mixture was effectively achieved with an enantiomeric excess (ee) of 99% for R-NX upon the initial solution run and 93% for S-NX upon the elution step.