Latest ArticlesN-formylation of amines, a class of synthetically important reactions, is typically conducted using metal catalysts that are relatively expensive or not readily available and usually needs harsh conditions to increase the reaction efficiency. Here, an efficient continuous microflow strategy was developed for the gas-liquid visible-light photocatalytic N-formylation of piperidine, which achieved a reaction yield of 82.97% and a selectivity of > 99% at 12 min using cheap organic dye photocatalyst under mild reaction conditions. The influence of essential parameters, including light intensity, temperature and equivalents of the gas, additive and photocatalyst, on the reaction yield was systematically studied. Furthermore, kinetic investigations were conducted, exhibiting the dependence of reaction rate and equilibrium yield of N-formylpiperidine on light intensity, temperature and photocatalyst equivalent. The microflow photocatalytic approach established in this work, which realized a markedly higher space-time yield than the conventional batch method (37.9 vs. 0.212 mmol h−1 L−1), paves the way for the continuous, green and efficient synthesis of N-formamides.
Unnatural amino acids (UAAs) have broad applications in pharmaceutical sciences and biological studies. Current synthetic methods for UAAs mainly rely on asymmetric catalysis and often require several steps. There is a lack of direct and simple methods. To address this challenge, we designed the LADA (labeling-activation-desulfurization-addition) strategy: selective labeling and activation of cysteine residues, the photocatalytic desulfurization and the subsequent radical addition to alkenes. Although composed of two steps, it is one-pot synthesis and has advantages such as high functional group tolerance, biocompatible reaction condition, and retained stereochemistry. This highly efficient strategy was successfully applied in the direct synthesis of unnatural amino acids and modifications of peptides with more than 50 examples.
Immobilizing enzyme to nano interfaces has demonstrated to be a favorable strategy for prompting the industrialized application of enzyme. Despite tremendous endeavor has been devoted to using gold nanoparticles (AuNPs) as conjugation matrix due to its fascinating physico-chemical properties, maintaining enzymatic activity while circumventing cumbersome modification remains a formidable challenge. Herein, the freezing-directed conjugation of enzyme/nano interfaces was constructed without extra reagent. As the proof of concept, glucose oxidase (GOx) was chosen as model enzyme. The one-pot conjugation process can be facilely completed at −20 ℃ under aqueous solution. Moreover, with the loading of GOx on AuNP at freezing, the enzyme exhibited superior catalytic activity and stability upon thermal and pH perturbation. The mechanism of boosted activity was then discussed in detail. It was found that higher loading density under freezing condition and more enzyme tending to bind AuNPs via Au-S bond were the main factors for the superior activity. More importantly, this methodology was universal and can also be applied to other enzyme which contains natural cysteine, such as horseradish peroxidase (HRP) and papain. This facile conjugation strategy accompanied by remarkable bioactivity expand the possibilities for enzymatic biosensing, microdevice and even drug delivery.
A series of photoinduced palladium-catalyzed 1,3-diene-selective fluoroalkylamination derivatives was rationally synthesized based on diversity-oriented synthesis via cross coupling of 1,3-dienes, amines and fluoroalkyl iodides. The reaction featured good function group tolerance and a broad substrate scope, which could be extended to the late-stage modification of bioactive molecules. Bactericidal activity of all the compounds against Xanthomonas oryzae pv. oryzae (Xoo) was evaluated. Among them, compound E14 showed significant activity against Xanthomonas oryzae pv. oryzae (Xoo) with half maximal effective concentration (EC50) value of 6.61 µmol/mL. In pot experiments, the results showed that E14 could control rice bacterial blight with protective and curative efficiencies of 37.5% and 63.2% at 200 µg/mL, respectively. Additionally, a plausible mechanism for antibacterial behavior of E14 was proposed by electron microscopy, flow cytometry, reactive oxygen species detection, and biofilm assay. In current work, it can promote the development of photoinduced palladium-catalyzed 1,3-diene-selective fluoroalkyl amination compounds as prospective antibacterial agent bearing an intriguing mode of action.
A general, facile and eco-friendly iron catalysis enables oxidation of unstrained tertiary aromatic alcohols to ketones through C−C bond cleavage even with H2O2 as the oxidant. Notably, this transformation can tolerate oxidation-labile functional groups. The robustness of this method is further demonstrated on the late-stage oxidation of complex bioactive molecules.
The rapid and precise fabrication of multiscale supramolecular assemblies using micro/nanofluidic techniques has emerged as a dynamic area of research in supramolecular chemistry, materials chemistry, and organic chemistry. This review summarizes the application of micro/nanofluidic techniques in constructing supramolecular assemblies, including nanoscale supramolecular assemblies such as macrocycles and cages, microscale supramolecular assemblies such as metal organic frameworks (MOFs) and covalent organic frameworks (COFs), and macroscale supramolecular assemblies such as supramolecular hydrogels. Compared to conventional synthesis methods, micro/nanofluidic techniques for the production of supramolecular assemblies have significant advantages, including enhanced safety, high reaction rates, improved selectivity/yield, and scalability. Additionally, micro/nanofluidic systems facilitate the creation of precisely controllable micro/nanoconfined environments, allowing for a unique flow behavior that improves our understanding of the supramolecular self-assembly process. Such systems may also lead to the development of novel supramolecular assemblies that differ from those generated via traditional methods.
Four pillar[5]arene-based bicyclic compounds, so-called molecular universal joint (MUJ), were synthesized by incorporating a bisamide ring containing N, O, or S-heteroatom groups, which served as stimuli-responsive chiroptical molecular devices. The structure of MUJ was confirmed by 1H NMR spectra and single-crystal X-ray diffraction analysis, and their planar-chiral enantiomers were successfully separated. Chiroptical inversion behaviors from in to out configurations triggered by temperature, solvent, and guest complexation were investigated by circular dichroism spectra. Chiroptical inversion could be realized in the presence of adiponitrile in certain solvents due to the solvation effects on the side ring and the threading of the guest into the pillar[5]arene cavity. However, the stronger self-included interactions between the cavity and the inside ring of certain MUJs led to inhibition of the switching.
It is challenging to cooperatively improve the nonlinear optical (NLO) efficiency and the laser-induced damage threshold (LIDT). This work reports a novel IR NLO materials CsInP2S7 (CIPS) designed by combination the strategies of alkali metals substitution and microscopic NLO units PS4 introduction based on AgGaS2. CIPS was composed of strongly distorted [InS6]9- octahedra and [P2S7]4- dimers constructed by corner-sharing [PS4]3-, which increase the NLO efficiency and decrease thermal expansion anisotropy simultaneously. Compared with AgGaS2, CIPS exhibited strong phase matchable NLO response ca. 1.1 × AGS@2.1 µm, high LIDT ca. 20.8 × AgGaS2, and IR transparency up to 15.3 µm. Structural analysis and theoretical investigation confirmed that large SHG effect and ultrahigh LIDT of CIPS originated from the synergistic contribution of [InS6]9- octahedra and [P2S7]4- dimers. These results indicate that CIPS is a promising NLO candidate in the mid-IR region, and this study provides a new approach for developing potential NLO-LIDT compatible materials.
Carbon nanofibers (CNFs) have received extensive and in-depth studied as anodes for sodium-ion batteries (SIBs), and yet their initial Coulombic efficiency and rate capability remain enormous challenge at practical level. Herein, CNFs anchored with cobalt nanocluster (CNFs-Co) were prepared using chemical vapor deposition and thermal reduction methods. The as-prepared CNFs-Co shows a high initial Coulombic efficiency of 91% and a high specific discharge capacity of 246 mAh/g at 0.1 A/g after 200 cycles as anode for SIBs. Meanwhile, the CNFs-Co anode still delivers a high cycling stability with 108 mAh/g after 1000 cycles at 10 A/g. These excellent electrochemical properties could be attributed to the involved spin state Co, which endows CNFs with large interplanar spacing (0.39 nm) and abundant vacancy defects. Importantly, the spin state Co downshifts the p-band center of carbon and strengthens the Na+ adsorption energy from −2.33 eV to −2.64 eV based on density functional theory calculation. This novel strategy of modulating the carbon electronic structure by the spin state of magnetic metals provides a reference for the development of high-performance carbon-based anode materials.
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