One-pot synthesis of multisubstituted imidazoles under solvent-free conditions and microwave irradiation using Fe<inf>3</inf>O<inf>4</inf>@SiO<inf>2</inf>-imid-PMA<sup>n</sup> magnetic porous nanospheres as a recyclable catalyst
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© The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015. An efficient, green and ecofriendly procedure has been developed using Fe < inf > 3 < /inf > O < inf > 4 < /inf > @SiO < inf > 2 < /inf > -imid-PMA < sup > n < /sup > as a magnetic catalyst for a rapid and improved synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles under solvent-free conditions and microwave irradiation in excellent yields. The reactions under conventional heating conditions were compared with the microwave-assisted reactions. The operational simplicity, practicability and applicability of this protocol to various substrates make it an interesting alternative to previous procedures. The present approach offers several advantages such as short reaction times, high yields, simplicity of operation, easy work-up, a cleaner reaction and ease of recovery and reusability of the catalyst using a magnetic field. Also, the nanocatalyst can be easily recovered by the application of a magnetic field and reused for the next reactions at least 5 times without distinct deterioration in catalytic activity. SEM, BET, DLS and leaching of the catalyst after each reaction cycle were investigated.