5 research outputs found

    Highly <i>trans-</i>Stereoselective Synthesis of Bicyclic Isoxazolidines via Copper-Catalyzed Triple Cascade Catalysis

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    A triple cascade was developed using a simple copper catalyst to <i>trans</i>-selectively access bicyclic isoxazolidines in a one-pot synthesis. This strategy features the in situ generation of nitrones and subsequent trapping by [3 + 2] cycloaddition. In this method, copper serves three catalytic functions: as a Lewis acid for the ene reaction, as an organometallic for aerobic oxidation, and as a Lewis acid for an <i>endo</i>-selective [3 + 2] cycloaddition. The successful merging of aerobic oxidation and Lewis acid catalysis demonstrated efficient cascade synergy

    Highly <i>trans-</i>Stereoselective Synthesis of Bicyclic Isoxazolidines via Copper-Catalyzed Triple Cascade Catalysis

    No full text
    A triple cascade was developed using a simple copper catalyst to <i>trans</i>-selectively access bicyclic isoxazolidines in a one-pot synthesis. This strategy features the in situ generation of nitrones and subsequent trapping by [3 + 2] cycloaddition. In this method, copper serves three catalytic functions: as a Lewis acid for the ene reaction, as an organometallic for aerobic oxidation, and as a Lewis acid for an <i>endo</i>-selective [3 + 2] cycloaddition. The successful merging of aerobic oxidation and Lewis acid catalysis demonstrated efficient cascade synergy

    Highly <i>trans-</i>Stereoselective Synthesis of Bicyclic Isoxazolidines via Copper-Catalyzed Triple Cascade Catalysis

    No full text
    A triple cascade was developed using a simple copper catalyst to <i>trans</i>-selectively access bicyclic isoxazolidines in a one-pot synthesis. This strategy features the in situ generation of nitrones and subsequent trapping by [3 + 2] cycloaddition. In this method, copper serves three catalytic functions: as a Lewis acid for the ene reaction, as an organometallic for aerobic oxidation, and as a Lewis acid for an <i>endo</i>-selective [3 + 2] cycloaddition. The successful merging of aerobic oxidation and Lewis acid catalysis demonstrated efficient cascade synergy

    Gated Water Transport through Graphene Nanochannels: From Ionic Coulomb Blockade to Electroosmotic Pump

    No full text
    Understanding and controlling water or ion transport in nanochannels plays an important role in further unravelling the transport mechanism of biological membrane channels and designing functional nanofluidic devices. Molecular dynamics simulations were conducted to investigate water and ion transport in graphene nanochannels. Similar to electron coulomb blockade phenomenon observed in quantum dots, we discovered an ionic coulomb blockade phenomenon in our graphene nanochannels, and another two ion transport modes were also proposed to rationalize the observed phenomena under different electric-field intensities. Furthermore, on the basis of this blockade phenomenon we found that the Open and Closed states of the graphene nanochannels for water transport could be switched according to external electric-field intensities, and electroosmotic flow could further enhance the water transport. These findings might have potential applications in designing and fabricating controllable valves in lab-on-chip nanodevices

    Double-Edged Role of VOCs Reduction in Nitrate Formation: Insights from Observations during the China International Import Expo 2018

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    Aerosol nitrate (NO3–) constitutes a significant component of fine particles in China. Prioritizing the control of volatile organic compounds (VOCs) is a crucial step toward achieving clean air, yet its impact on NO3– pollution remains inadequately understood. Here, we examined the role of VOCs in NO3– formation by combining comprehensive field measurements conducted during the China International Import Expo (CIIE) in Shanghai (from 10 October to 22 November 2018) and multiphase chemical modeling. Despite a decline in primary pollutants during the CIIE, NO3– levels increased compared to pre-CIIE and post-CIIENO3– concentrations decreased in the daytime (by βˆ’10 and βˆ’26%) while increasing in the nighttime (by 8 and 30%). Analysis of the observations and backward trajectory indicates that the diurnal variation in NO3– was mainly attributed to local chemistry rather than meteorological conditions. Decreasing VOCs lowered the daytime NO3– production by reducing the hydroxyl radical level, whereas the greater VOCs reduction at night than that in the daytime increased the nitrate radical level, thereby promoting the nocturnal NO3– production. These results reveal the double-edged role of VOCs in NO3– formation, underscoring the need for transferring large VOC-emitting enterprises from the daytime to the nighttime, which should be considered in formulating corresponding policies
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