Lewis or Brønsted acidic methylimidazolium ionic liquid-functionalized Fe 3 O 4 @SiO 2 nanoparticles were fabricated and applied as an efficient magnetic heterogeneous catalyst for dibenzothiophene (DBT) oxidation in a biphasic system using H 2 O 2 as the oxidant. The structures of catalysts were characterized by SEM, TEM, XRD, TGA, FT-IR, VSM and EDX techniques. The magnetic catalysts showed high catalytic performance in the oxidation of DBT in an n-hexane/acetonitrile biphasic system using H 2 O 2 , and high conversions were obtained. The effects of contact time, temperature, amount of H 2 O 2 and amount of catalyst on the DBT oxidative removal efficiency were investigated. The contact time of 60 min, 0.1 g catalyst, and 4 mL H 2 O 2 at 313 K were found as optimal experimental conditions for an improved DBT oxidative removal process. The sulfur level could be lowered from 100 ppm to less than 7, 5, and 2 ppm under optimal conditions for Fe 3 O 4 @SiO 2 -Mim-BF 4 , Fe 3 O 4 @SiO 2 -Mim-HSO 4 , and Fe 3 O 4 @SiO 2 -Mim-FeCl 4 , respectively. These nanomagnetic heterogeneous catalysts could be easily separated from the reaction mixture by applying an external magnetic field and recycled several times.Scheme 1 Preparation of Fe 3 O 4 @SiO 2 -methylimidazolium chloride.
This journal isScheme 2 Schematic illustration of Fe 3 O 4 @SiO 2 -methylimidazolium chloride nanoparticles anion exchange. 34976 | RSC Adv., 2017, 7, 34972-34983 This journal isFig. 6 Energy dispersive X-ray spectroscopy of (a) Fe 3 O 4 @SiO 2 -Mim-BF 4 (b) Fe 3 O 4 @SiO 2 -Mim-HSO 4 and (c) Fe 3 O 4 @SiO 2 -Mim-FeCl 4 . This journal is Scheme 4 The suggested mechanism of DBT oxidation by Fe 3 O 4 @SiO 2 -Mim-BF 4 . This journal is Scheme 5 The suggested mechanism of DBT oxidation by Fe 3 O 4 @SiO 2 -Mim-HSO 4 . 34980 | RSC Adv., 2017, 7, 34972-34983 This journal is
Please cite this article as: Abdolhamid Alizadeh, Mohammad Mehdi Khodaei, Mitra Fakhari, Gisya Abdi, Sohrab Ghouzivand, Chemo and regioselective serendipitous electrochemically initiated spirocyclization of caffeic acid esters with barbituric acid derivatives, Electrochimica Acta http://dx.
Abstract
HOGraphite + R 1 = H or CH 3 R = Methyl or Ethyle or Isopropyl 1 2 6 I or II 2H + , 2e -An interesting sequence of oxidation/Michael addition/oxidation/spirocyclization is observed in the electrolysis of caffeic acid esters in the presence of barbituric acid derivatives leading to the synthesis of a series of novel spirocycles. In an experimentally simple and clean procedure, the electrolyses proceed via a domino of electrochemical (E) and chemical (C) events with employing electrons as the only reagents in aqueous solution without introducing any catalyst or oxidant. From mechanistic point of view, a new type of domino mechanism (ECEC i , C i =spirocyclization) is proven with a unique C i phenomenon at final step. Also, in light of experimental and theoretical NMR investigations, highly chemo and regioselectivities have been detected in these synthetic electrolyses.
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