Magnetic Co‐doped NiFe₂O₄ Nanocomposite: A Heterogeneous and Recyclable Catalyst for the One‐Pot Synthesis of Benzimidazoles, Benzoxazoles and Benzothiazoles under Solvent‐Free Conditions

Abstract

A simple and efficient procedure for the synthesis of benzimidazoles, benzoxazoles, and benzothiazoles via the condensation of o‐phenylenediamine, o‐aminophenol, and o‐aminothiophenol with various benzaldehydes by using magnetic Co‐doped NiFe2O4 nanoparticles has been developed. This nanocatalyst has advantages such as excellent product yields, solvent‐free conditions, and very short reaction times. After any experiment, the magnetic nanocatalyst could be easily separated with the aid of an external magnet and reused at least four times without any loss of its catalytic performance.

CoNiFe2O4@Silica‐SO3H nanoparticles: New recyclable magnetic nanocatalyst for the one‐pot synthesis of 3,4‐dihydropyrimidin‐2(1H)‐ones/thiones under solvent‐free conditions

“…Furthermore, the heterogeneous catalysts, particularly the magnetic nanoparticles (MNPs), have achieved much interest in organic reactions. [ 1,2 ] The MNPs easily removed from the products by using an external magnet and recycled. Based on our previous achievements in the preparation of MNPs as catalysts, [ 2,3 ] in this study, sulfuric acid‐functionalized silica‐coated magnetic CoNiFe 2 O 4 nanoparticles (CoNiFe 2 O 4 @Silica‐SO 3 H) has been synthesized.…”

“…[ 1,2 ] The MNPs easily removed from the products by using an external magnet and recycled. Based on our previous achievements in the preparation of MNPs as catalysts, [ 2,3 ] in this study, sulfuric acid‐functionalized silica‐coated magnetic CoNiFe 2 O 4 nanoparticles (CoNiFe 2 O 4 @Silica‐SO 3 H) has been synthesized. This novel magnetically recoverable catalyst has been characterized by Fourier‐transform infrared spectroscopy (FT‐IR), scanning electron microscope (SEM), energy dispersive X‐ray spectroscopy (EDS), X‐ray diffraction spectroscopy (XRD) spectroscopies, vibrating sample magnetometer (VSM) analysis, and applied as acidic nanocatalyst for the preparation of 3,4‐dihydropyrimidin‐2(1 H )‐ones/thiones derivatives by the Biginelli reaction.…”

Synthesis, characterization, and catalytic application of Fe3O4‐Si‐[CH2]3‐N=CH‐aryl for the efficient synthesis of novel poly‐substituted pyridines

“…Also, the catalytic activity of MNPs can be improved via functionalization and modification of their surface by organic compounds . Furthermore, functionalized MNPs are a suitable replacement for the conventional homogeneous and heterogeneous catalysts that are used in the industry and organic reactions . Their good catalytic activities are due to their ability to join different functional groups, their magnetism, their thermal stability, and their strong inorganic layer …”

Sulfur‐Promoted Synthesis of Benzoxazoles from 2‐Aminophenols and Aldehydes

“…[1], [2] The most commonly used synthetic approach to such molecules involve condensation of 2-aminophenols with carboxylic acids [3], [4] or derivatives [5], [6] under non oxidant conditions or with alcohols, [7], [8] amines, [9], [10] ketones, [11] aldehydes, [12]- [15] methylarenes [16] or related compounds [17] in the presence of an oxidant or at high temperatures with concomitant dehydrogenation. [18]- [19] However, most of the traditional synthetic methods required strongly acidic conditions [6] , prolonged heating at high temperatures and significant amounts of catalysts [14] (including expensive/toxic transition metal catalysts) [5], [7], [13], [15]- [16], [18]- [21] as well as toxic/harmful reagents and solvents. [3],[4], [8], [12], [16] Although the aerobic oxidation [12], [15], [20]- [21] is in general very green because of its high atom economy with water as the only stoichiometric byproduct in most cases, a major drawback of using oxygen as an oxidant is the risk of explosion of flammable organic substrates, especially in large-scale syntheses at reaction temperatures above the flashpoint of the reaction components.…”

“…[18]- [19] However, most of the traditional synthetic methods required strongly acidic conditions [6] , prolonged heating at high temperatures and significant amounts of catalysts [14] (including expensive/toxic transition metal catalysts) [5], [7], [13], [15]- [16], [18]- [21] as well as toxic/harmful reagents and solvents. [3],[4], [8], [12], [16] Although the aerobic oxidation [12], [15], [20]- [21] is in general very green because of its high atom economy with water as the only stoichiometric byproduct in most cases, a major drawback of using oxygen as an oxidant is the risk of explosion of flammable organic substrates, especially in large-scale syntheses at reaction temperatures above the flashpoint of the reaction components. Moreover, due to its gaseous state, exact stoichiometric control of oxygen amounts used in the reaction is not readily possible.…”