Organocatalytic Asymmetric (4 + 3) Cycloaddition toward Optically Active Cyclohepta Fused Diindoles.

A novel asymmetric (4 + 3) cycloaddition of indole-2,3-quinodimethanes in situ generated from 3-methyl-2-indolylmethanols with 3-indolylmethanols via chiral phosphoric acid catalysis has been established. The cycloaddition reaction exhibits a broad substrate scope affording the diverse enantioenriched cyclohepta fused diindoles in high yields with good enantioselectivities. Significantly, this work represents the first application of 3-methyl-2-indolylmethanols as 4C synthons instead of the commonly reported three-atom synthons in cycloaddition reactions.

Organocatalytic enantioselective (4+3) cyclization for the synthesis of spiro-fused heterocyclic compounds containing isoindolinone, oxepine and indole moieties.

A refined strategy has been developed to control the regioselective asymmetric (4+3) cyclization of α-(3-isoindolinonyl) propargylic alcohols with 2-indolylmethanols, utilizing chiral phosphoric acid catalysis. This innovative organocatalytic cyclization yields spiro isoindolinone-oxepine-fused indoles featuring a spiro-quaternary stereocenter in high yields and enantioselectivities, facilitated by the solvent of 1,1-dichloro-1-fluoroethane and the additive of hexafluoroisopropanol. Additionally, the photophysical properties of product 3k are examined, revealing bright fluorescence both in the solution and the solid state.

Strong metal-support interactions of TiO2 interface-loaded Pt constructed under different atmospheres for adjusting the hydrogen storage reaction performance of N-ethylcarbazole.

In this study, two series of samples (rT-Pt/TiO2 prepared with a hydrogen pretreatment and Tr-Pt/TiO2 prepared with an oxygen pretreatment) were prepared by treating commercial TiO2 supports in different atmospheres to establish different TiO2 interfacial structures, followed by the addition of platinum nanoparticles (NPs) for the catalyzed hydrogenation/dehydrogenation cycle of N-ethylcarbazole (NEC). The kinetic analysis and reaction mechanism were investigated by combining XRD, Raman, CO-DRIFT, HRTEM, XPS, H2-TPD and DFT calculations. It was found that the performance of the samples for the NEC system's cyclic hydrogen storage could be modulated by treating the TiO2 interfacial structure with different atmospheres varying the extent of strong metal-support interaction (SMSI). In addition, a turnover frequency (TOF) of 191.52 min-1 for dehydrogenation was achieved at 170 °C, which is better than the previously reported catalysts. Experimental studies (characterization and kinetic studies) and DFT calculations confirmed that the SMSI of the Tr-Pt/TiO2 series samples promoted the escape of H2 and enhanced the catalytic activity for 4H-NEC in the 12H-NEC dehydrogenation reaction. In the NEC hydrogenation reaction, the rT-Pt/TiO2 series samples were pretreated with H2 before loading platinum metal, which led to the early activation of Ti4+ in their carriers, and thus suppressed the SMSI effect of the reduction process after loading platinum. This process caused the interface formed by rT-Pt/TiO2 to have a higher energy barrier to 6H-NEC, which is an intermediate product of the NEC hydrogenation process, and this interrupted the hydrogenation process of 6H-NEC.

Synthesis, Characterization, and Evaluation of a Hindered Phenol-Linked Benzophenone Hybrid Compound as a Potential Polymer Anti-Aging Agent.

Hindered phenol antioxidants and benzophenone UV absorbers are common polymer additives and often used in combination applications to enhance the anti-aging performance of polymer materials. This study primarily aims to incorporate hindered phenol and benzophenone structures into a single molecule to develop a multifunctional polymer additive with good anti-aging performance. Thus, a novel potential polymer anti-aging agent, namely 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid 3-(4-benzoyl-3-hydroxyphenoxy)propyl ester (3C), was synthesized using 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, 3-bromo-1-propanol, and 2,4-dihydroxybenzophenone as raw materials by two-step procedure. The structure of compound 3C was characterized by nuclear magnetic resonance (NMR), high-resolution mass spectrometry (HRMS), Fourier-transform infrared (FT-IR) spectroscopy, and X-ray single crystal diffraction. Its thermal stability and UV resistance were assessed using thermogravimetric analysis (TGA) and UV absorption spectroscopy (UV). The compound 3C as an additive was incorporated into the preparation of polyolefin elastomer (POE) films. The anti-aging performance of POE films was evaluated by measuring parameters such as oxidation induction time, melt flow index, transmittance, and infrared spectra of the artificially aged POE films. The results indicate that the compound 3C exhibits a promising anti-aging performance in both thermo-oxidative aging and ultraviolet aging tests of POE films and is a potential polymer anti-aging agent.

Temporally resolved proteomics identifies nidogen-2 as a cotarget in pancreatic cancer that modulates fibrosis and therapy response.

Pancreatic ductal adenocarcinoma (PDAC) is characterized by increasing fibrosis, which can enhance tumor progression and spread. Here, we undertook an unbiased temporal assessment of the matrisome of the highly metastatic KPC (Pdx1-Cre, LSL-KrasG12D/+, LSL-Trp53R172H/+) and poorly metastatic KPflC (Pdx1-Cre, LSL-KrasG12D/+, Trp53fl/+) genetically engineered mouse models of pancreatic cancer using mass spectrometry proteomics. Our assessment at early-, mid-, and late-stage disease reveals an increased abundance of nidogen-2 (NID2) in the KPC model compared to KPflC, with further validation showing that NID2 is primarily expressed by cancer-associated fibroblasts (CAFs). Using biomechanical assessments, second harmonic generation imaging, and birefringence analysis, we show that NID2 reduction by CRISPR interference (CRISPRi) in CAFs reduces stiffness and matrix remodeling in three-dimensional models, leading to impaired cancer cell invasion. Intravital imaging revealed improved vascular patency in live NID2-depleted tumors, with enhanced response to gemcitabine/Abraxane. In orthotopic models, NID2 CRISPRi tumors had less liver metastasis and increased survival, highlighting NID2 as a potential PDAC cotarget.

Wet peroxide oxidation process catalyzed by Cu/Al2O3: phenol degradation and Cu2+ dissolution behavior.

Catalytic wet peroxide oxidation (CWPO) has become an important deep oxidation technology for organics removal in wastewater treatments. Supported Cu-based catalysts belong to an important type of CWPO catalyst. In this paper, two Cu catalysts, namely, Cu/Al2O3-air and Cu/Al2O3-H2 were prepared and evaluated through catalytic degradation of phenol. It was found that Cu/Al2O3-H2 had an excellent catalytic performance (TOC removal rate reaching 96%) and less metal dissolution than the Cu/Al2O3-air case. Moreover, when the organic removal rate was promoted at a higher temperature, the metal dissolution amounts was decreased. Combined with hydroxyl radical quenching experiments, a catalytic oxidation mechanism was proposed to explain the above-mentioned interesting behaviors of the Cu/Al2O3-H2 catalyst for CWPO. The catalytic test results as well as the proposed mechanism can provide better guide for design and synthesis of good CWPO catalysts.

Exploring Tunable Properties, Solvent-Modulated Dynamics, and Novel C(sp3)-H Activation Mechanisms in Electron Donor-Acceptor Complexes.

Electron donor-acceptor (EDA) complex photochemistry has emerged as a vibrant area in visible-light-mediated synthetic radical chemistry. However, theoretical insights into the reaction mechanisms remain limited. Our study investigates the influence of solvent polarity and halogen atom types on radical reaction pathways in EDA complexes. We demonstrate that solvent polarity modulates the charge transfer and spatial arrangement within EDA complexes, thereby influencing their stability and reaction kinetics. Iodide ions play a crucial role in facilitating free radical generation and stabilizing reaction intermediates. Different halogen atom types exhibit distinct effects on radical reactions. Variations in radical concentration and solvent environment further affect the pathway selectivity. Additionally, light conditions influence the free radical generation and pathway selectivity. Our findings enhance the understanding of EDA complex photochemistry and radical reactions, offering insights for organic synthesis and photochemistry applications.

Support Effect of Boron Nitride on the First N-H Bond Activation of NH3 on Ru Clusters.

Support effect is an important issue in heterogeneous catalysis, while the explicit role of a catalytic support is often unclear for catalytic reactions. A systematic density functional theory computational study is reported in this paper to elucidate the effect of a model boron nitride (BN) support on the first N-H bond activation step of NH3 on Run (n = 1, 2, 3) metal clusters. Geometry optimizations and energy calculations were carried out using density functional theory (DFT) calculation for intermediates and transition states from the starting materials undergoing the N-H activation process. The primary findings are summarized as follows. The involvement of the model BN support does not significantly alter the equilibrium structure of intermediates and transition states in the most favorable pathway (MFP). Moreover, the involvement of BN support decreases the free energy of activation, ΔG≠, thus improving the reaction rate constant. This improvement is more obvious at high temperatures like 673 K than low temperatures like 298 K. The BN support effect leading to the ΔG≠ decrease is most significant for the single Ru atom case among all three cases studied. Finally, the involvement of the model BN may change the spin transition behavior of the reaction system during the N-H bond activation process. All these findings provide a deeper insight into the support effect on the N-H bond activation of NH3 for the supported Ru catalyst in particular and for supported transition metal catalysts in general.

Retraction: Enantioselective synthesis of α-tetrasubstituted (3-indolizinyl) (diaryl)methanamines via chiral phosphoric acid catalysis.

[This retracts the article DOI: 10.1039/D2RA03750E.].

Enantioselective synthesis of α-tetrasubstituted (1-indolizinyl) (diaryl)-methanamines via chiral phosphoric acid catalysis.

An enantioselective Friedel-Crafts reaction of cyclic α-diaryl N-acyl imines with indolizines catalyzed by a chiral spirocyclic phosphoric acid has been developed. The asymmetric transformation proceeds smoothly to afford α-tetrasubstituted (1-indolizinyl) (diaryl)methanamines in good yields with up to 98% ee under mild conditions.

Enantioselective Self-Assembly of a Homochiral Tetrahedral Cage Comprising Only Achiral Precursors.

How Nature synthesizes enantiomerically pure substances from achiral or racemic resources remains a mystery. In this study, we aimed to emulate this natural phenomenon by constructing chiral tetrahedral cages through self-assembly, achieved by condensing two achiral compounds-a trisamine and a trisaldehyde. The occurrence of intercomponent CH⋅⋅⋅π interactions among the phenyl building blocks within the cage frameworks results in twisted conformations, imparting planar chirality to the tetrahedrons. In instances where the trisaldehyde precursor features electron-withdrawing ester side chains, we observed that the intermolecular CH⋅⋅⋅π forces are strong enough to prevent racemization. To attain enantioselective self-assembly, a chiral amine was introduced during the imine formation process. The addition of three equivalents of chiral amino mediator to one equivalent of the achiral trisaldehyde precursor formed a trisimino intermediate. This chiral compound was subsequently combined with the achiral trisamino precursor, leading to an imine exchange reaction that releasing the chiral amino mediator and formation of the tetrahedral cage with an enantiomeric excess (ee) of up to 75 %, exclusively composed of achiral building blocks. This experimental observation aligns with theoretical calculations based on the free energies of related cage structures. Moreover, since the chiral amine was not consumed during the imine exchange cycle, it enabled the enantioselective self-assembly of the tetrahedral cage for multiple cycles when new batches of the achiral trisaldehyde and trisamino precursors were successively added.

Selective Adsorptive Desulfurization with Alkaline-Earth Metal-Modified Zeolites in Oil in the Presence of Olefin.

Adsorptive desulfurization (ADS) was a hopeful method for deep desulfurization of oil in mild conditions. In this paper, based on the alkaline-earth (AE) metal-modified Y zeolite (AEY), synthesis, systematic characterization, ADS performance test, and analysis of related adsorption mechanisms were carried out. The crystal and pore structure of Y zeolite were not damaged after ion exchange of AE, while the amount of acid sites and the ratio of Lewis/Bronsted acid sites were both decreased. Although surface acid sites on zeolites were believed to be active sites for ADS, the performance test results showed that AEY adsorbents had rather good S adsorption capacity compared to NaY. Moreover, the S adsorption selectivity in the presence of hexene-1 in oil was also desirable for all AEY adsorbents. Based on these experimental results and previously proposed mechanisms for S-containing compound adsorption, a new adsorption mechanism was proposed for AEY, and this mechanism was further supported by the aid of DFT calculations. The good S-removal performance of AEY adsorbents as well as the new proposed adsorption mechanism may help people design and synthesize further improved S-compound adsorbents for ADS processes in an oil refinery.

A density functional theory study on the adsorption of different organic sulfides on boron nitride nanosheet.

The adsorption of methanethiol (MT), thiophene (T), benzothiophene (BT), dibenzothiophene (DBT) on hexagonal boron nitride (h-BN) has been investigated by the framework of the density functional theory (DFT) calculations in this work. The prefer adsorption sites and interfacial angles of different sulfur compounds on the surface of the h-BN are investigated and analyzed. The adsorption energy results indicated that the adsorption of MT (Ead ≈ -6 kcal mol-1), T (Ead ≈ -10 kcal mol-1), BT (Ead ≈ -15 kcal mol-1), and DBT (Ead ≈ -21 kcal mol-1) on monolayer h-BN is physical interaction, and the value of Ead on bilayer h-BN is more than that on monolayer h-BN 0.05%. Adsorptive conformations show that sulfides prefer to be adsorbed on center B atoms rather than N atoms. Meanwhile, thiophene and its analogues tend to be adsorbed parallel on h-BN plane. Energy decomposition, natural population analysis (NPA), and electrostatic potential (ESP) analysis used to better understand the nature of adsorption on h-BN. van der Waals force plays a dominant role in adsorption process. Due to the π-π interactions, T, BT, and DBT have larger van der Waals forces than MT and the value of adsorption energy is negative correlated to the number of benzene rings. These findings are helpful for deeper understanding the adsorptive desulfurization mechanism and help develop better adsorbents for desulfurization in the future.

Organocatalytic Tandem Synthesis of Chiral Hexacyclic Bisindoles from Propargylic 3-Methyleneindoles with 2-Indolylmethanols.

A novel chiral phosphoric acid-catalyzed tandem regioselective 1,6-addition/double intramolecular nucleophilic addition annulation of the propargylic 3-methyleneindoles in situ generated from α-indolyl propargylic alcohols with 2-indolylmethanols has been developed. The methodology afforded the new chiral trifluoromethyl pentalenobisindoles bearing an all-carbon quaternary stereogenic center in generally good yields with excellent enantioselectivities.

Supported Ni Catalysts: Simple Vapor Deposition Preparation Method and Improved Catalytic Performance for Oxidative Dehydrogenation of Ethane.

Developing new methods of catalyst preparation is one of the most important tasks in the field of catalysis. A simple one-tube vapor deposition (VD) is provided in this paper for preparing the supported Ni catalyst. Ni(acac)2 was used as the Ni precursor. This preparation method was successfully applied to three types of catalytic supports, that is, Al2O3 and zeolites 5A and Hß. Varying Ni contents of less than 8 wt % can be obtained by employing different conditions. The Ni content, depending on different deposition conditions, was preliminarily explored. The catalytic performance for oxidative dehydrogenation of ethane (ODHE) was tested for the prepared Ni catalysts by the VD method. Several cases of catalytic tests showed that for the same Ni content, the VD-prepared Ni catalyst presented better performance for ODHE than the one prepared by a traditional impregnation method. Besides the improvement in catalytic performance, several advantages of our VD preparation method for catalysis are discussed.

On the mechanism of acceptorless dehydrogenation of N-heterocycles catalyzed by tBuOK: a computational study.

The catalytic acceptorless dehydrogenation (ADH) of saturated N-heterocycles has recently gained considerable attention as a promising strategy for hydrogen release from liquid organic hydrogen carriers (LOHCs). Recently, a simple tBuOK base-promoted ADH of N-heterocycles was developed by Yu et al. (Adv. Synth. Catal. 2019, 361, 3958). However, it is still open as to how the tBuOK plays a catalytic role in the ADH process. Herein, our density functional study reveals that the tBuOK catalyzes the ADH of 1,2,3,4-tetrahydroquinoline (THQ) through a quasi-metal-ligand bifunctional catalytic channel or a base-catalyzed pathway with close energy barriers. The hydride transfer in the first dehydrogenation process is determined to be the rate determining step, and the second dehydrogenation can proceed directly from 34DHQ regulated by the tBuOK. In addition, the computational results show that the cooperation of a suitable alkali metal ion with the tBuO- group is so critical that the tBuOLi and the isolated tBuO- are both inferior to tBuOK as a dehydrogenation catalyst.

Chiral spirocyclic phosphoric acid-catalyzed enantioselective synthesis of heterotriarylmethanes bearing an amino acid moiety.

We present herein an enantioselective protocol for the chiral phosphoric acid-catalyzed addition of 3-arylisoxazol-5-amines to highly reactive 3-methide-3H-pyrroles to provide a diverse range of heterotriarylmethanes bearing an amino acid moiety in good yields (up to 97%) and high enantioselectivities (up to 93% ee) under mild conditions. The chiral spirocyclic phosphoric acid is crucial in converting the initial 1H-pyrrol-3-yl carbinols into reactive 3-methide-3H-pyrroles and obtaining the good enantiocontrol, thereby facilitating the desired enantioselective transformation.

Pericapsular nerve group (PENG) block for early pain management of elderly patients with hip fracture: a single-center double-blind randomized controlled trial.

BACKGROUND: The pericapsular nerve group block (PENG) is a novel technique that blocks the articular branches of the hip joint. This study aimed to compare its effectiveness to a sham block in elderly patients with hip fractures. METHOD: A randomized double-blind controlled trial was conducted in elderly patients with intertrochanteric and neck of femur fractures. Patients were randomized to receive either PENG block or a sham block. Postblock, systemic analgesia was titrated using a standardized protocol of acetaminophen, oral morphine or patient-controlled analgesia. The primary outcome was the dynamic pain score (Numerical Rating Scale 0-10) at 30 min postblock. Secondary outcomes included pain scores at multiple other time points and 24-hour opioid consumption. RESULTS: 60 patients were randomized and 57 completed the trial (PENG n=28, control n=29). Patients in PENG group had significantly lower dynamic pain scores at 30 min compared with control group (median (IQR) 3 (0.5-5) vs 5 (3-10), p<0.01). For the secondary outcomes, dynamic pain scores were lower in PENG group at 1 hour (median (IQR) 2 (1-3.25) vs 5 (3-8), p<0.01) and 3 hours postblock (median (IQR) 2 (0-5) vs 5 (2-8), p<0.05). Patients in PENG group had lower 24-hour opioid consumption (median (IQR) oral morphine equivalent dose 10 (0-15) vs 15 (10-30) mg, p<0.05). CONCLUSION: PENG block provided effective analgesia for acute traumatic pain following hip fracture. Further studies are required to validate the superiority of PENG blocks over other regional techniques. TRIAL REGISTRATION NUMBER: NCT04996979.