A Brønsted‐Acidic Ionic Liquid Gel as an Efficient and Recyclable Heterogeneous Catalyst for the Synthesis of Bis(indolyl)methanes under Solvent‐Free Sonication

Abstract

AB rønsted-acidic ionic liquid gel was prepared from 1-(4-sulfonic acid)butyl-3-methylimidazolium hydrogen sulfate and tetraethoxysilane. Its structural characterization was accomplished by FTIR, TGA, SEM, EDS, and ICP-OES. The ionic liquid gel promotes the synthesis of bis(indolyl)methanes. Interestingly,t his catalyst allowst he preparation of bis(indolyl)methanes in good to excellenty ields within a short reaction time, through ac lean and straightforward procedure. Moreover,t he ionic liquid gel can be recovered by filtration and can be reused up to 5t imes without any detectable loss of catalytic performance. Additionally,t he methodh as aw ide substrate scope and provides an accessible route for the large-scale direct synthesis of bis(indolyl)-methanes.

A magnetic self-contained thermochromic system with convenient temperature range

“…Chromic behaviour has also been reported for many Co 2+ complexes in solution 11 and in ionic liquids where the Co 2+ salts may be dissolved 12 or indeed constitute a primary component of the molten salt mixture. 13 In 2015 Nockemann and co-workers showed that such a switch was possible in a frozen solution of a cobaltcontaining ionic liquid at inconvenient sub-zero temperatures. 12 Here, we report a comprehensive optical and magnetic study on a rare example of the Oh-Td switching in a cobalt-containing IL, prepared with sustainable materials, over the useful temperature range of 20-60 °C.…”

Porous metal oxides derived from Cu–Al layered double hydroxide as an efficient heterogeneous catalyst for the Friedel–Crafts alkylation of indoles with benzaldehydes under microwave irradiation

“…After calcination of LDH at high temperatures, MMO is obtained with the large surface area and many M 2+ , M 3+ Lewis acidic sites [42] . Base on our experiments and previous literature [ 15 , 16 , 43 , 44 ], a proposed mechanism for MMO-catalyzed the Friedel–Crafts alkylation of indoles with aromatic aldehydes is presented in Fig. 7 .…”

Au Nanostructures with Controlled Morphology, Biosynthesized from Garcinia cowa Fruit Extract, and Their Use in Microwave‐Mediated Bisindole Synthesis

“…In the presence of GCF-Au NPs, the electrophilicity of carbonyl carbon is enhanced, [56] inducing reaction with indole [57] to provide the intermediate A. The corresponding intermediate 3-arylidene-3H-indole B subsequently react with another indole to afford the expected product C. [58] Table 5 represents catalysts reported in the literature for the similar transformation (Scheme 1) and shows GCF-Au NPs as a catalyst with improved catalytic efficacy, very low reaction time, easy catalyst preparation method and low catalyst amount in the proposed methodology.…”