The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform

Emanuele Attolino - One of the best experts on this subject based on the ideXlab platform.

  • regiospecific synthesis of 4 deoxy d threo hex 3 enopyranosides by simultaneous activation elimination of the talopyranoside axial 4 oh with the nah im2so2 system manifestation of the Stereoelectronic Effect
    European Journal of Organic Chemistry, 2006
    Co-Authors: Emanuele Attolino, Giorgio Catelani, Felicia Dandrea
    Abstract:

    A new and high-yielding method for the regioselective preparation of 4-deoxy- and 2,4-dideoxy-2-acetamido-β-D-threo-hex-3-enopyranosides has been developed. The process involves a simultaneous activation–elimination of the OH-4 group of β-D-talopyranosides and 2-acetamido-2-deoxy-β-D-talopyranosides, mediated by the NaH/N,N′-sulfuryldiimidazole system at –30 °C. The same reaction applied on the analogous β-D-galactopyranosides takes place without any regioselectivity, affording mixtures of hex-3- and hex-4-enopyranosides. In the case of the methyl 2,3,6-tri-O-benzyl-α-D-talo- and α-D-galactopyranosides, the corresponding 4-O-imidazylates can be isolated by quenching the reactions at –30 °C. Upon warming these crude products to room temperature, the α-talo-4-O-imidazylate gives the corresponding hex-3-eno derivative in very high yield, but its α-galacto analogue gives the hex-4-enopyranoside enol ether in poor yield. The different regiochemical outcome between the talo and the galacto series has been attributed to the Stereoelectronic Effect exerted, exclusively in talo-configured compounds, by the axially disposed C-2 electronegative substituent, which selectively accelerates the breaking of the antiperiplanar C(3)–H bond. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

  • Regiospecific synthesis of 4-deoxy-D-threo -hex -3 -enopyranosides by simultaneous activation-elimination of the talopyranoside axial 4-OH with the NaH/Im2SO2 system : Manifestation of the Stereoelectronic Effect
    European Journal of Organic Chemistry, 2006
    Co-Authors: Emanuele Attolino, Giorgio Catelani, Felicia D'andrea
    Abstract:

    A new and high-yielding method for the regioselective preparation of 4-deoxy- and 2,4-dideoxy-2-acetamido-β-D-threo-hex-3-enopyranosides has been developed. The process involves a simultaneous activation–elimination of the OH-4 group of β-D-talopyranosides and 2-acetamido-2-deoxy-β-D-talopyranosides, mediated by the NaH/N,N′-sulfuryldiimidazole system at –30 °C. The same reaction applied on the analogous β-D-galactopyranosides takes place without any regioselectivity, affording mixtures of hex-3- and hex-4-enopyranosides. In the case of the methyl 2,3,6-tri-O-benzyl-α-D-talo- and α-D-galactopyranosides, the corresponding 4-O-imidazylates can be isolated by quenching the reactions at –30 °C. Upon warming these crude products to room temperature, the α-talo-4-O-imidazylate gives the corresponding hex-3-eno derivative in very high yield, but its α-galacto analogue gives the hex-4-enopyranoside enol ether in poor yield. The different regiochemical outcome between the talo and the galacto series has been attributed to the Stereoelectronic Effect exerted, exclusively in talo-configured compounds, by the axially disposed C-2 electronegative substituent, which selectively accelerates the breaking of the antiperiplanar C(3)–H bond. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Felicia D'andrea - One of the best experts on this subject based on the ideXlab platform.

  • Regiospecific synthesis of 4-deoxy-D-threo -hex -3 -enopyranosides by simultaneous activation-elimination of the talopyranoside axial 4-OH with the NaH/Im2SO2 system : Manifestation of the Stereoelectronic Effect
    European Journal of Organic Chemistry, 2006
    Co-Authors: Emanuele Attolino, Giorgio Catelani, Felicia D'andrea
    Abstract:

    A new and high-yielding method for the regioselective preparation of 4-deoxy- and 2,4-dideoxy-2-acetamido-β-D-threo-hex-3-enopyranosides has been developed. The process involves a simultaneous activation–elimination of the OH-4 group of β-D-talopyranosides and 2-acetamido-2-deoxy-β-D-talopyranosides, mediated by the NaH/N,N′-sulfuryldiimidazole system at –30 °C. The same reaction applied on the analogous β-D-galactopyranosides takes place without any regioselectivity, affording mixtures of hex-3- and hex-4-enopyranosides. In the case of the methyl 2,3,6-tri-O-benzyl-α-D-talo- and α-D-galactopyranosides, the corresponding 4-O-imidazylates can be isolated by quenching the reactions at –30 °C. Upon warming these crude products to room temperature, the α-talo-4-O-imidazylate gives the corresponding hex-3-eno derivative in very high yield, but its α-galacto analogue gives the hex-4-enopyranoside enol ether in poor yield. The different regiochemical outcome between the talo and the galacto series has been attributed to the Stereoelectronic Effect exerted, exclusively in talo-configured compounds, by the axially disposed C-2 electronegative substituent, which selectively accelerates the breaking of the antiperiplanar C(3)–H bond. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Felicia Dandrea - One of the best experts on this subject based on the ideXlab platform.

  • regiospecific synthesis of 4 deoxy d threo hex 3 enopyranosides by simultaneous activation elimination of the talopyranoside axial 4 oh with the nah im2so2 system manifestation of the Stereoelectronic Effect
    European Journal of Organic Chemistry, 2006
    Co-Authors: Emanuele Attolino, Giorgio Catelani, Felicia Dandrea
    Abstract:

    A new and high-yielding method for the regioselective preparation of 4-deoxy- and 2,4-dideoxy-2-acetamido-β-D-threo-hex-3-enopyranosides has been developed. The process involves a simultaneous activation–elimination of the OH-4 group of β-D-talopyranosides and 2-acetamido-2-deoxy-β-D-talopyranosides, mediated by the NaH/N,N′-sulfuryldiimidazole system at –30 °C. The same reaction applied on the analogous β-D-galactopyranosides takes place without any regioselectivity, affording mixtures of hex-3- and hex-4-enopyranosides. In the case of the methyl 2,3,6-tri-O-benzyl-α-D-talo- and α-D-galactopyranosides, the corresponding 4-O-imidazylates can be isolated by quenching the reactions at –30 °C. Upon warming these crude products to room temperature, the α-talo-4-O-imidazylate gives the corresponding hex-3-eno derivative in very high yield, but its α-galacto analogue gives the hex-4-enopyranoside enol ether in poor yield. The different regiochemical outcome between the talo and the galacto series has been attributed to the Stereoelectronic Effect exerted, exclusively in talo-configured compounds, by the axially disposed C-2 electronegative substituent, which selectively accelerates the breaking of the antiperiplanar C(3)–H bond. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Na Xin - One of the best experts on this subject based on the ideXlab platform.

  • Atomically Precise Engineering of Single-Molecule Stereoelectronic Effect.
    Angewandte Chemie (International ed. in English), 2021
    Co-Authors: Sheng Meng, Linan Meng, Na Xin, Jingying Wang, Shizhao Ren, Zhuang Yan, Miao Zhang, Cheng Shen, Guangyu Zhang
    Abstract:

    Charge transport in a single-molecule junction is extraordinarily sensitive to both the internal electronic structure of molecule and its microscopic environment. Two distinct conductance states of a prototype terphenyl molecule are observed, corresponding to the bistability of outer phenyl rings at each end. An azobenzene unit is intentionally introduced through atomically precise side-functionalization at the central ring of the terphenyl, which is reversibly isomerized between trans and cis forms by either electric or optical stimuli. Both experiment and theory demonstrate that the azobenzene side-group delicately modulates charge transport in the backbone via single-molecule Stereoelectronic Effect. We reveal that the dihedral angle between the central and outer phenyl ring, as well as the corresponding rotation barrier, is subtly controlled by isomerization, while the behaviors of the phenyl ring away from the azobenzene are hardly affected. This tunability offers a new route to precisely engineer multiconfigurational single-molecule memories, switches, and sensors.

  • Stereoelectronic Effect-Induced Conductance Switching in Aromatic Chain Single-Molecule Junctions
    Nano letters, 2017
    Co-Authors: Na Xin, Jinying Wang, Chuancheng Jia, Zitong Liu, Xisha Zhang, Shuopei Wang, Yao Gong, Hantao Sun
    Abstract:

    Biphenyl, as the elementary unit of organic functional materials, has been widely used in electronic and optoelectronic devices. However, over decades little has been fundamentally understood regarding how the intramolecular conformation of biphenyl dynamically affects its transport properties at the single-molecule level. Here, we establish the Stereoelectronic Effect of biphenyl on its electrical conductance based on the platform of graphene-molecule single-molecule junctions, where a specifically designed hexaphenyl aromatic chain molecule is covalently sandwiched between nanogapped graphene point contacts to create stable single-molecule junctions. Both theoretical and temperature-dependent experimental results consistently demonstrate that phenyl twisting in the aromatic chain molecule produces different microstates with different degrees of conjugation, thus leading to stochastic switching between high- and low-conductance states. These investigations offer new molecular design insights into buildin...

  • Stereoelectronic Effect-Induced Conductance Switching in Aromatic Chain Single-Molecule Junctions
    2017
    Co-Authors: Na Xin, Jinying Wang, Chuancheng Jia, Zitong Liu, Xisha Zhang, Shuopei Wang, Yao Gong, Hantao Sun
    Abstract:

    Biphenyl, as the elementary unit of organic functional materials, has been widely used in electronic and optoelectronic devices. However, over decades little has been fundamentally understood regarding how the intramolecular conformation of biphenyl dynamically affects its transport properties at the single-molecule level. Here, we establish the Stereoelectronic Effect of biphenyl on its electrical conductance based on the platform of graphene-molecule single-molecule junctions, where a specifically designed hexaphenyl aromatic chain molecule is covalently sandwiched between nanogapped graphene point contacts to create stable single-molecule junctions. Both theoretical and temperature-dependent experimental results consistently demonstrate that phenyl twisting in the aromatic chain molecule produces different microstates with different degrees of conjugation, thus leading to stochastic switching between high- and low-conductance states. These investigations offer new molecular design insights into building functional single-molecule electrical devices

  • Stereoelectronic Effect-Induced Conductance Switching in Aromatic Chain Single-Molecule Junctions
    NANO LETTERS, 2017
    Co-Authors: Na Xin, Wang Jinying, Jia Chuancheng, Liu Zitong, Zhang Xisha, Yu Chenmin, Li Mingliang, Wang Shuopei, Gong Yao, Sun Hantao
    Abstract:

    Biphenyl, as the elementary unit of organic functional materials, has been widely used in electronic and optoelectronic devices. However, over decades little has been fundamentally understood regarding how the intramolecular conformation of biphenyl dynamically affects its transport properties at the single-molecule level. Here, we establish the Stereoelectronic Effect of biphenyl on its electrical conductance based on the platform of graphene-molecule single-molecule junctions, where a specifically designed hexaphenyl aromatic chain molecule is covalently sandwiched between nanogapped graphene point contacts to create stable single-molecule junctions. Both theoretical and temperature-dependent experimental results consistently demonstrate that phenyl twisting in the aromatic chain molecule produces different microstates with different degrees of conjugation, thus leading to stochastic switching between high- and low-conductance states. These investigations offer new molecular design insights into building functional single-molecule electrical devices.National Natural Science Funds of China [21225311, 91333102, 21373014, 11222431]; 973 Project [2012CB921404]SCI(E)ARTICLE2856-8611

Giorgio Catelani - One of the best experts on this subject based on the ideXlab platform.

  • regiospecific synthesis of 4 deoxy d threo hex 3 enopyranosides by simultaneous activation elimination of the talopyranoside axial 4 oh with the nah im2so2 system manifestation of the Stereoelectronic Effect
    European Journal of Organic Chemistry, 2006
    Co-Authors: Emanuele Attolino, Giorgio Catelani, Felicia Dandrea
    Abstract:

    A new and high-yielding method for the regioselective preparation of 4-deoxy- and 2,4-dideoxy-2-acetamido-β-D-threo-hex-3-enopyranosides has been developed. The process involves a simultaneous activation–elimination of the OH-4 group of β-D-talopyranosides and 2-acetamido-2-deoxy-β-D-talopyranosides, mediated by the NaH/N,N′-sulfuryldiimidazole system at –30 °C. The same reaction applied on the analogous β-D-galactopyranosides takes place without any regioselectivity, affording mixtures of hex-3- and hex-4-enopyranosides. In the case of the methyl 2,3,6-tri-O-benzyl-α-D-talo- and α-D-galactopyranosides, the corresponding 4-O-imidazylates can be isolated by quenching the reactions at –30 °C. Upon warming these crude products to room temperature, the α-talo-4-O-imidazylate gives the corresponding hex-3-eno derivative in very high yield, but its α-galacto analogue gives the hex-4-enopyranoside enol ether in poor yield. The different regiochemical outcome between the talo and the galacto series has been attributed to the Stereoelectronic Effect exerted, exclusively in talo-configured compounds, by the axially disposed C-2 electronegative substituent, which selectively accelerates the breaking of the antiperiplanar C(3)–H bond. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

  • Regiospecific synthesis of 4-deoxy-D-threo -hex -3 -enopyranosides by simultaneous activation-elimination of the talopyranoside axial 4-OH with the NaH/Im2SO2 system : Manifestation of the Stereoelectronic Effect
    European Journal of Organic Chemistry, 2006
    Co-Authors: Emanuele Attolino, Giorgio Catelani, Felicia D'andrea
    Abstract:

    A new and high-yielding method for the regioselective preparation of 4-deoxy- and 2,4-dideoxy-2-acetamido-β-D-threo-hex-3-enopyranosides has been developed. The process involves a simultaneous activation–elimination of the OH-4 group of β-D-talopyranosides and 2-acetamido-2-deoxy-β-D-talopyranosides, mediated by the NaH/N,N′-sulfuryldiimidazole system at –30 °C. The same reaction applied on the analogous β-D-galactopyranosides takes place without any regioselectivity, affording mixtures of hex-3- and hex-4-enopyranosides. In the case of the methyl 2,3,6-tri-O-benzyl-α-D-talo- and α-D-galactopyranosides, the corresponding 4-O-imidazylates can be isolated by quenching the reactions at –30 °C. Upon warming these crude products to room temperature, the α-talo-4-O-imidazylate gives the corresponding hex-3-eno derivative in very high yield, but its α-galacto analogue gives the hex-4-enopyranoside enol ether in poor yield. The different regiochemical outcome between the talo and the galacto series has been attributed to the Stereoelectronic Effect exerted, exclusively in talo-configured compounds, by the axially disposed C-2 electronegative substituent, which selectively accelerates the breaking of the antiperiplanar C(3)–H bond. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)