Diastereoselective Synthesis of Functionalized Spirocyclopropyl Oxindoles via P(NMe₂)₃‑Mediated Reductive Cyclopropanation

A P­(NMe₂)₃-mediated reductive cyclopropanation reaction of α-keto esters or amides with isatin-derived alkenes has been developed, providing efficient and diastereoselective synthesis of highly functionalized spirocyclopropyl oxindoles bearing two all-carbon quaternary centers. This reaction also represents a complementary and nonmetal-involving protocol for the challenging cyclopropanation of electron-deficient alkenes

Adsorption and Diffusion of <i>n</i>‑Heptane and Toluene over Mesoporous ZSM‑5 Zeolites

ZSM-5 zeolites with different mesoporosities were prepared by alkaline treatment and characterized by powder XRD and nitrogen adsorption. Two C₇ hydrocarbons of <i>n</i>-heptane and toluene were employed as probe molecules to investigate the effects of the introduction of mesopore on the adsorption and diffusion properties of ZSM-5 zeolites by comparing the experimental results of the samples treated and untreated by using NaOH. Adsorption isotherms were measured gravimetrically in the pressure range 0–32 mbar and from 293 to 338 K. The isotherms of microporous and mesoporous ZSM-5 were successfully fitted by using the Langmuir–Freundlich model and the dual-site Langmuir–Freundlich model, respectively. Henry’s constants and the initial heats of adsorption calculated from the adsorption isotherms as well as the fitting parameters displayed that the interactions between adsorbent and adsorbate were weakened after the introduction of mesopore, and the interactions between the adsorbates with microporous surface are much stronger than that between them with the mesoporous surface. Diffusion measurements were undertaken using the zero length column (ZLC) technique at partial pressure of <i>p</i>/<i>p</i>₀ < 0.000 15 from 333 to 393 K. The results showed that the effective diffusion constants (<i>D</i>_eff/<i>R</i>²) of the two C₇ hydrocarbons increased greatly in the presence of mesopores, while the corresponding activation energy decreased due to the reduced diffusion resistance and the shortened diffusion path in the mesoporous zeolites. Also, higher and much more dramatic enhancement of the efficient diffusivities as a function of mesoporous volume for toluene relative to that for <i>n</i>-heptane were found, indicating that the diffusion of <i>n</i>-heptane is controlled by the micropore diffusion and that the diffusion of toluene is exclusively determined by mass transfer through the mesopores

Ratiometric Fluorescent Probe for Rapid Detection of Bisulfite through 1,4-Addition Reaction in Aqueous Solution

A ratiometric fluorescent probe based on a positively charged benzo­[<i>e</i>]­indolium moiety for bisulfite is reported. The bisulfite underwent a 1,4-addition reaction with the C-4 atom in the ethylene group. This reaction resulted in a large emission wavelength shift (Δλ = 106 nm) and an observable fluorescent color change from orange to cyan. The reaction could be completed in 90 s in a PBS buffer solution and displayed high selectivity and sensitivity for bisulfite. A simple paper test strip system was developed to detect bisulfite rapidly. Probe <b>1</b> was used to detect bisulfite in real samples with good recovery

Big World in the Small Space: Constructing Hollow Zeolite Microspheres Using a Sustainable Template

Hollow zeolite microspheres have attracted considerable interest due to their unique properties and great potential applications. In this work, we report a simple and cost-effective approach for constructing hollow zeolite microspheres based on a biomass-derived template, i.e., carboxymethylcellulose sodium (CMC). As an example, a hollow ZSM-5 microsphere with a hollow core smaller than 1 μm in diameter and a complete crystal shell is synthesized. This approach overcomes most of the limitations associated with the existing methods, such as complex operations and costly spherical templates. By studying the growth process in detail, a possible formation mechanism is proposed. The crystallization of the hollow zeolite microsphere is through a “surface to core” process, in which the interaction between the CMC and the zeolite gel and the decomposition of the polymer network play the critical roles

Applications of α‑Phosphonovinyl Tosylates in the Synthesis of α‑Arylethenylphosphonates via Suzuki–Miyaura Cross-Coupling Reactions

It has been demonstrated for the first time that α-phosphonovinyl tosylates could efficiently couple with a range of arylboronic acids to access α-arylethenylphosphonates. The unprecedented procedure exhibits excellent functional group tolerance, giving the terminal vinylphosphonates in good to excellent isolated yields (60–99%) under mild reaction conditions

Chemoselective P(NMe₂)₃‑Mediated Reductive Epoxidation between Two Different Carbonyl Electrophiles: Synthesis of Highly Functionalized Unsymmetrical Epoxides

Herein, we report a chemoselective P­(NMe₂)₃-mediated reductive epoxidation of α-dicarbonyl compounds such as isatins, α-keto esters, and α-diketones with aldehydes and ketones, leading to an efficient synthesis of a wide range of highly functionalized unsymmetrical epoxides in moderate to excellent yields and diastereoselectivities. The Kukhtin–Ramirez adduct, which is exclusively generated in situ from an α-dicarbonyl compound and P­(NMe₂)₃, plays a key role in governing the chemoselectivity. It represents the first practical synthesis of unsymmetrical epoxides via direct reductive epoxidation of two different carbonyl electrophiles and also complements the existing methods of generating epoxides

Chemoselective P(NMe₂)₃‑Mediated Reductive Epoxidation between Two Different Carbonyl Electrophiles: Synthesis of Highly Functionalized Unsymmetrical Epoxides

Herein, we report a chemoselective P­(NMe₂)₃-mediated reductive epoxidation of α-dicarbonyl compounds such as isatins, α-keto esters, and α-diketones with aldehydes and ketones, leading to an efficient synthesis of a wide range of highly functionalized unsymmetrical epoxides in moderate to excellent yields and diastereoselectivities. The Kukhtin–Ramirez adduct, which is exclusively generated in situ from an α-dicarbonyl compound and P­(NMe₂)₃, plays a key role in governing the chemoselectivity. It represents the first practical synthesis of unsymmetrical epoxides via direct reductive epoxidation of two different carbonyl electrophiles and also complements the existing methods of generating epoxides

Immobilization of Highly Dispersed Ag Nanoparticles on Carbon Nanotubes Using Electron-Assisted Reduction for Antibacterial Performance

Silver nanoparticles (Ag NPs) supported on certain materials have been widely used as disinfectants. Yet, to date, the antibacterial activity of the supported Ag NPs is still far below optimum. This is mainly associated with the easy aggregation of Ag NPs on the supporting materials. Herein, an electron-assisted reduction (EAR) method, which is operated at temperatures as low as room temperature and without using any reduction reagent, was employed for immobilizing highly dispersed Ag NPs on aminated-CNTs (Ag/A-CNTs). The average Ag NPs size on the EAR-prepared Ag/A-CNTs is only 3.8 nm, which is much smaller than that on the Ag/A-CNTs fabricated from the traditional thermal calcination (25.5 nm). Compared with Ag/A-CNTs fabricated from traditional thermal calcination, EAR-prepared Ag/A-CNTs shows a much better antibacterial activity to <i>E. coli</i>/<i>S. aureus</i> and antifouling performance to <i>P. subcordiformis</i>/<i>T. lepidoptera</i>. This is mainly originated from the significantly enhanced Ag⁺ ion releasing rate and highly dispersed Ag NPs with small size on the EAR-prepared Ag/A-CNTs. The findings from the present work are helpful for fabricating supported Ag NPs with small size and high dispersion for efficient antibacterial process

Flowerlike Hierarchical Y with Dramatically Increased External Surface: A Potential Catalyst Contributing to Improving Precracking for Bulky Reactant Molecules

Crude oil is becoming more and more difficult to refine because of increasingly large heavy oil molecules. Increased external surface of catalysts contributes to promoting precracking of heavy or extra-heavy oil molecules. Flowerlike hierarchical Y zeolite with considerably increased external surface was synthesized without using any organic templates by a hydrothermal procedure. Because the isolated nanoparticles are unstable, the primary nanocrystals gather via self-assembly into loose aggregates. The inner crystals, which act as the “pistils”, are difficult to grow because of the confined spaces, while the outer crystals in the aggregates can further grow and form the oriented sheet “petals”. The increased exterior surface offers the catalysts dramatically elevated conversion when tested in the catalytic cracking of triisopropylbenzene. The result also suggests that the activity of the catalysts in large reactant involved reactions may generally depend on its external surface properties

Enhancement of Two-Photon Fluorescence and Low Threshold Amplification of Spontaneous Emission of Zn-processed CuInS₂ Quantum Dots

Heavy-metal-free I–III–VI₂ quantum dots (QDs) have recently emerged as favorable alternatives to toxic II–VI QDs for optoelectronic and biological applications, but low fluorescence efficiency is a key issue related to the promising nanocrystals. In this work, we demonstrate big enhancement of two-photon fluorescence efficiency and low threshold two-photon pumped amplification of spontaneous emission (ASE) of Zn-processed CuInS₂ (CIS) QDs for the first time. The change of two-photon process caused by Zn²⁺ cation exchange in CIS QDs is systematically investigated. Two-photon ASE in Zn-processed CIS QDs films is achieved with a record of low threshold fluence of 5.7 μJ/cm². With high two-photon fluorescence quantum yields and low threshold ASE, the Zn-processed CIS QDs could become a promising candidate for two-photon bioimaging, nonlinear optical and novel QDs laser devices