2-Aminoethanesulfonic acid immobilized on epichlorohydrin functionalized Fe3O4@WO3 (Fe3O4@WO3-EAE-SO3H (III)): A heterogeneous and reusable nanocatalyst for synthesis of α,α'-bis (substituted-benzylidene) cycloalkanones in solvent-free conditions

A green, efficient, chemoselective, facile and clean procedure is described and discussed for the synthesis of α, α'-bis (substituted-benzylidene) cycloalkanones in solvent-free conditions. The condensation reaction was carried out through the reaction of aromatic aldehydes with cycloalkanones in the presence of Fe3O4@WO3 (Fe3O4@WO3-EAE-SO3H (III)) nanoparticles as the catalyst. The nanostructured catalyst with the spherical shape, particle size in the range of 7-23 nm and superparamagnetic behavior may be referred as an excellent replacement for Brønsted acids. The reaction proceeds rapidly at room temperature, giving high yields of products. No self-condensation product was produced. Easy separation of the catalyst from the reaction mixture by means of an external magnetic field and re-using up to seven times without loss of activity are the salient features of the present method.