The Experts below are selected from a list of 369 Experts worldwide ranked by ideXlab platform

Viktor V. Zhdankin - One of the best experts on this subject based on the ideXlab platform.

Q.a Wang - One of the best experts on this subject based on the ideXlab platform.

Chaojie Li - One of the best experts on this subject based on the ideXlab platform.

Roberta Bernini - One of the best experts on this subject based on the ideXlab platform.

  • Synthesis of Biologically Active Catecholic Compounds via ortho-Selective Oxygenation of Phenolic Compounds Using Hypervalent Iodine(V) Reagents
    Current Organic Synthesis, 2012
    Co-Authors: Roberta Bernini, Giancarlo Fabrizi, Laurent Pouységu, Denis Deffieux, Stéphane Quideau
    Abstract:

    A review. Catecholic motifs are present in numerous natural products and synthetic compds. used in various sectors of the chem. industries such as food, cosmetic, pharmaceutical and polymer industries. The antioxidant activity usually conferred to compds. bearing catecholic motifs is the property on which their application is often based. Although several (bio) chem. methods are available to chemists to produce catechols, the oxygenation of phenols constitutes one of the most practical approaches as long as the o-​selectivity of the process can be controlled. In this context, oxygenating hypervalent iodine(V) reagents offer a convenient metal-​free soln. Among these reagents, 2-​iodoxybenzoic Acid (IBX) or its stabilized (non explosive) SIBX and polymer-​supported versions have found the most useful and successful applications in the conversion of phenols into o-​quinones, followed by redn. into catechols. Examples of oxygenative demethylation of 2-​methoxyphenols and o-​hydroxylation of phenolic compds. for the synthesis of biol. and industrially-​relevant catechols are highlighted in this review article, together with some mechanistic discussions on these transformations

  • Synthesis and Structure/Antioxidant Activity Relationship of Novel Catecholic Antioxidant Structural Analogues to Hydroxytyrosol and Its Lipophilic Esters
    Journal of Agricultural and Food Chemistry, 2012
    Co-Authors: Roberta Bernini, Maurizio Barontini, Fernanda Crisante, Daniela Tofani, Valentina Balducci, Augusto Gambacorta
    Abstract:

    A large panel of novel catecholic antioxidants and their fatty Acid or methyl carbonate esters has been synthesized in satisfactory to good yields through a 2-Iodoxybenzoic Acid (IBX)-mediated aromatic hydroxylation as the key step. The new catechols are structural analogues of naturally occurring hydroxytyrosol (3,4-DHE). To evaluate structure/activity relationships, the antioxidant properties of all catecholic compounds were evaluated in vitro by ABTS assay and on whole cells by DCF fluorometric assay and compared with that of the corresponding already known hydroxytyrosyl derivatives. Results outline that all of the new catechols show antioxidant capacity in vitro higher than that of the corresponding hydroxytyrosyl derivatives. Less evident positive effects have been detected in whole cells experiments. Cytotoxicity experiments, using MTT assay, on a representative set of compounds evidenced no influence in cell survival.

  • Convenient Synthesis of 1-Aryl-dihydroxyisochromans Exhibiting Antioxidant Activity
    Current Organic Chemistry, 2012
    Co-Authors: Roberta Bernini, Fernanda Crisante, Giancarlo Fabrizi, Patrizia Gentili
    Abstract:

    Several 1-aryl-hydroxy and dihydroxyisochromans were synthesized by a two-steps procedure based on the oxa-Pictet-Spengler reaction performed for the first time in dimethyl carbonate (DMC) from phenethyl alcohols and substituted benzaldehydes followed by the regioselective aromatic hydroxylation/oxidative aromatic demethylation with 2-Iodoxybenzoic Acid (IBX)/sodium dithionite (Na2S2O4) system. Some of them showed a novel pattern of hydroxylation degree into A ring. All synthesized isochromans were tested about their radical scavenging activity by 2,2-diphenyl-2-picrylhydrazyl radical (DPPH center dot) method. Experimental results showed that dihydroxyisochromans were more active than the corresponding phenolic or guaiacolic parent compounds confirming the key role of the catecholic moiety for the antioxidant activity

  • Selective and Efficient Oxidative Modifications of Flavonoids with 2-Iodoxybenzoic Acid (IBX).
    ChemInform, 2010
    Co-Authors: Maurizio Barontini, Roberta Bernini, Fernanda Crisante, Giancarlo Fabrizi
    Abstract:

    A regioselective aromatic hydroxylation of a variety of flavanones and flavones using IBX or a polystyrene-supported IBX is demonstrated.

  • Selective and efficient oxidative modifications of flavonoids with 2-Iodoxybenzoic Acid (IBX)
    Tetrahedron, 2010
    Co-Authors: Maurizio Barontini, Roberta Bernini, Fernanda Crisante, Giancarlo Fabrizi
    Abstract:

    Abstract 2-Iodoxybenzoic Acid (IBX), a mild and efficient hypervalent iodine oxidant, has been utilised in different reaction conditions to perform several efficient oxidative modifications of flavonoids. Fine-tuning of the reaction conditions allowed remarkably selective modifications of these compounds. At room temperature, IBX proved to be an excellent reagent for a highly regioselective aromatic hydroxylation of monohydroxylated flavanones and flavones, generating the corresponding catecholic derivatives showing high antioxidant activity. At 90 °C, IBX efficiently dehydrogenated a large panel of methoxylated flavanones to their corresponding flavones exhibiting anticancer activity. IBX polystyrene has also been utilised to increase the recovery of highly polar compounds. Following the first oxidation, the reagent was recovered and reused in several runs without loss of efficiency and selectivity. The first example of an application of IBX polystyrene in a dehydrogenation reaction has been described.

Jarugu Narasimha Moorthy - One of the best experts on this subject based on the ideXlab platform.

  • One-Pot Synthesis of 4-Carboalkoxy-Substituted Benzo[h]coumarins from α- and β-Naphthols and Their Excited-State Properties.
    ACS omega, 2019
    Co-Authors: Ajeet Chandra, Kanyashree Jana, Jarugu Narasimha Moorthy
    Abstract:

    One-pot synthesis has been developed for 4-carboethoxybenzo[h]coumarins starting from α-/β-naphthols. Accordingly, diverse 4-carboethoxybenzocoumarins can be synthesized in moderate-to-excellent (31–75%) isolated yields. The synthesis involves initial oxidation of naphthols to the intermediary 1,2-naphthoquinones with 2-Iodoxybenzoic Acid followed by a cascade of reactions, namely, Wittig olefination, Michael addition, β-elimination, and cyclization. Furthermore, we have comprehensively investigated the excited-state properties of differently substituted 4-carboalkoxybenzo[h]coumarins. It is shown that they exhibit low to high fluorescence quantum yields (1–36%) and excited-state lifetimes (ca. 1–7 ns) depending on the substitution pattern and solvent employed.

  • One-pot synthesis of α-bromo- and α-azidoketones from olefins by catalytic oxidation with in situ-generated modified IBX as the key reaction
    Tetrahedron, 2017
    Co-Authors: Ajeet Chandra, Keshaba Nanda Parida, Jarugu Narasimha Moorthy
    Abstract:

    Abstract Simple one-pot protocols for the syntheses of α-bromoketones and α-azidoketones starting from olefins have been developed by employing catalytic oxidation of the intermediary bromohydrins with in situ-generated modified IBX as the key reaction. The improved procedure involves initial formation of bromohydrin by the reaction of olefin with NBS in acetonitrile-water mixture (1:1) at rt followed by oxidation with in situ-generated 3,4,5,6-tetramethyl-2-Iodoxybenzoic Acid (TetMe-IBX), produced in catalytic amounts from 3,4,5,6-tetramethyl-2-iodobenzoic and Oxone. α-Bromoketones are further converted in the same pot to the corresponding α-azidoketones using NaN3/NaHCO3. The one-pot conversions are versatile for a variety of olefins that include cyclic as well as acyclic aliphatic olefins and electron-rich and electron-deficient styrenes. Chemoselective bromohydroxylation of electron-rich double bond and subsequent oxidation to the α-bromoketone is demonstrated for a substrate that contains both electron-rich and deficient double bonds.

  • Oxidative Cleavage of Olefins by in situ-Generated Catalytic 3,4,5,6-Tetramethyl-2-Iodoxybenzoic Acid/Oxone.
    ChemInform, 2015
    Co-Authors: Jarugu Narasimha Moorthy, Keshaba Nanda Parida
    Abstract:

    The reaction mechanism is described as initial dihydroxylation of the olefin with oxone, oxidative cleavage by in situ-generated 3,4,5,6-tetramethyl-2-Iodoxybenzoic Acid, and subsequent oxidation of the aldehyde functionality to the corresponding Acid with oxone again.

  • Oxidative cleavage of olefins by in situ-generated catalytic 3,4,5,6-tetramethyl-2-Iodoxybenzoic Acid/oxone.
    Journal of Organic Chemistry, 2014
    Co-Authors: Jarugu Narasimha Moorthy, Keshaba Nanda Parida
    Abstract:

    Oxidative cleavage of a variety of olefins to the corresponding ketones/carboxylic Acids is shown to occur in a facile manner with 3,4,5,6-tetramethyl-2-iodobenzoic Acid (TetMe-IA)/oxone. The simple methodology involves mere stirring of the olefin and catalytic amount (10 mol %) of TetMe-IA and oxone in acetonitrile–water mixture (1:1, v/v) at rt. The reaction mechanism involves initial dihydroxylation of the olefin with oxone, oxidative cleavage by the in situ-generated 3,4,5,6-tetramethyl-2-Iodoxybenzoic Acid (TetMe-IBX), and oxidation of the aldehyde functionality to the corresponding Acid with oxone. Differences in the reactivities of electron-rich and electron-poor double bonds have been exploited to demonstrate chemoselective oxidative cleavage in substrates containing two double bonds.