Efficient Fe^III‐Catalyzed Synthesis of Bis(indolyl)methanes in Ionic Liquids

Abstract

An efficient synthesis of bis(indolyl)methanes through FeIII‐catalyzed electrophilic substitution reactions of indoles with various aldehydes in ionic liquid is described. It was found that the ionic liquids involving FeCl3·6H2O were the most efficient catalytic systems, and could be simply recycled without significant loss of activity. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Iron Catalysis in Organic Synthesis

“…155 The yields for this transformation were excellent for many examples. Moreover, the ionic liquid together with the iron catalyst could be separated by extraction with diethyl ether.…”

cis-Dioxido-molybdenum(VI) complexes of tridentate ONO hydrazone Schiff base: Synthesis, characterization, X-ray crystal structure, DFT calculation and catalytic activity

“…Another factor that can be compared is the solvent. The reported method [42] used a complicated ionic liquid with high cost while our method uses a simple quaternary ammonium salt as solvent.…”

Synthesis of novel benzimidazole-diindolylmethane hybrid compounds within the green chemistry context

“…Its 13 C-NMR spectra showed 18 signals which corresponds to all magnetically inequivalent carbons. According to all of above, we think that our methodology to form compounds 3a-l has important green advantages over some previous mentioned synthetic methodologies for DIM derivatives, such as not use of solvent on reactions, compared with the use of dichloromethane 11,23,29,30,33,35 , chloroform 13,32 , acetonitrile 12,38 , ionic liquids 27,28,29 , not use of Broensted-Lowry and Lewis acid catalyst 11,12,13,23,25,26,30,32,33,34,37,39 , resins 31,35,36,38 , inert atmosphere 26 , and does not require long reaction times (7-10 h , with the use of microwave energy for the activation of reactions. In addition, to obtain benzimidazole compounds 4a-l we do not require any redox reagents, such as nitrobenzene 16 , sodium metabisulfite 17 , neither catalyst 16,18,22 or solvent.…”

“…In some cases, many byproducts were formed when the reactions were carried out in aqueous medium and under controlled conditions at pH values of 1.0, 1.5, 2.5 and 7.2, respectively. 24 In recent years, diindolylmethane synthesis has taken a greener direction, such as: using infrared energy in solvent-less conditions and in presence of a bentonitic clay, 25 with ultrasound energy and aminosulfonic acid as catalyst, 26 under microwave solvent-free irradiation with Lewis acid-catalysis, 27 in ionic liquids, [28][29][30] with SBA-15-supported poly [4-styrenesulfonyl(perfluorobutylsulfonyl)imide] as heterogeneous Broensted-Lowry acid catalyst, 31 using Montmorillonite K-10 clay, 32,33 with nickel nanoparticles as a reusable catalyst under solvent-free conditions, 34 employing ion exchange resins, 35,36 with eutectic salts, 37 synthesis mediated by Zeokarb-225, 38 and with zeolites, 14,39 amongst others.…”