Asymmetric Intermolecular Heck Reaction of Aryl Halides by Pd-histidine Organocatalysts
Abdol Reza Hajipour,
Zahra Khorsandi
Issue:
Volume 8, Issue 2, June 2020
Pages:
18-22
Received:
20 April 2020
Accepted:
5 May 2020
Published:
28 June 2020
Abstract: Extensive studies of asymmetric intermolecular Heck reaction are described and provide a deeper insight into histidine-catalyzed. In particular, aspects of enantio- as well as diastereoselectivity of these reactions are discussed. As the first report, we synthesized five histidine-based organocatalyts including histidine as a well-defined and biodegradable natural structure alone and in combination with 2,4,6-trichloro-1,3,5-triazine, benzene-1,3-diamine, dimethyl malonate and dimeric structure applied in the asymmetric intermolecular Heck reaction of aryl halides; their efficiency was compared to each other’s. These phosphine-free palladium catalysts were found as efficient catalytic system which provided the superior efficiency with excellent yields, regioselectivity and enantioselectivity. In these among, histidine with 2,4,6-trichloro-1,3,5-triazine which generate the star like molecule palladium catalyst gave the best activity in asymmetric intermolecular Heck reaction with excellent yields and good regio- and enantioselectivity under mild reaction conditions. The asymmetric intermolecular Heck reaction has been limited to aryl and vinyl triflates or aryl iodide in the rare reports of available Pd catalysts. Herein, we extend the reaction to aryl bromides. In addition, the scope of reaction was examined in two different techniques: conventional heating and microwave irradiation and compared. For the first time, microwave irradiation sintering is successfully used for this reaction. Comparison of catalytic activities of our catalyst (Pd/His) with literature examples confirmed our success.
Abstract: Extensive studies of asymmetric intermolecular Heck reaction are described and provide a deeper insight into histidine-catalyzed. In particular, aspects of enantio- as well as diastereoselectivity of these reactions are discussed. As the first report, we synthesized five histidine-based organocatalyts including histidine as a well-defined and biode...
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Batch Equilibrium and Kinetic Studies of Anionic and Cationic Dyes Adsorption onto Al−Pillared Clay from a Local Cameroonian Clay Materials in Aqueous Medium
Massai Harouna,
Constant Tcheka,
Narcisse Dobe
Issue:
Volume 8, Issue 2, June 2020
Pages:
23-32
Received:
29 July 2020
Accepted:
19 August 2020
Published:
27 August 2020
Abstract: The present work report removal of acid red 14 (AR14) and basic violet 3 (BV3) as anionic and cationic dyes, respectively, by adsorption process in batch mode from aqueous solution onto natural and modified forms of a local Cameroonian clay. The efficiency of these adsorbents materials (purified natural clay, P−Clay, sodium−clay, Na−Clay, and aluminium−pillared, Al−PILC) to remove dyes from aqueous medium was examined at different initial concentrations, pH, and ionic strengths. At the optimal contact time of 20 minutes, the maximum adsorbed dye amount on various adsorbents was obtained at pH 9 and pH 3 for AR14 and BV3 dyes, respectively. Adsorption process of both dyes on purified or modified clay was pH depend and the dyes molecules sorption over the clay surface occurs by electrostatic interactions. Ionic strength influenced significantly AR14 and BV3 dyes adsorption. Homo-ionization and pillaring clay increased its adsorption capacity. Kinetic studies showed that adsorption follows a pseudo−second−order model, and rate constants were evaluated. Non-linear fit of adsorption isotherm, qe vs Ce, were S−class for adsorption of both dye onto AL−PILC, indicating the heterogeneity of the adsorbent surface which leaded to a multilayer adsorption with interactions between dye molecules. Langmuir and Freundlich models were the best fits to the experimental data with the maximum adsorption capacities of AL−PILC for AR14 and BV3 dyes of 1.4 mg g-1 and 3.0 mg g-1, respectively. Lower adsorption capacities calculated from Langmuir isotherm model than the experimental values indicated adsorption mechanism occurs by multilayer formation on the adsorbent surface.
Abstract: The present work report removal of acid red 14 (AR14) and basic violet 3 (BV3) as anionic and cationic dyes, respectively, by adsorption process in batch mode from aqueous solution onto natural and modified forms of a local Cameroonian clay. The efficiency of these adsorbents materials (purified natural clay, P−Clay, sodium−clay, Na−Clay, and alumi...
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