Salen Complex of Cu(II) Supported on Superparamagnetic Fe3O4@SiO2Nanoparticles: An Efficient and Magnetically Recoverable Catalyst for the Synthesis of 1,4-Dihydropyridines

The Fe3O4@SiO2/Salen-Cu(II) nanocatalyst is reported as a thermally and air stable, economical,and magnetically recoverable heterogeneous catalyst for the selective and efficient 1,4-Dihydropyridines. Only by adding a small amount of the catalyst (0.4mol% Cu) to the reactantsand heating under air, the new presented method provides a variety of functionalized1,4-Dihydropyridines in good to excellent yields within short reaction times. The catalyst couldbe easily recovered with the aid of a permanent magnet and reused up to five consecutive runswithout significant loss of activity. Also, the leaching of Cu was negligible after the fifth recycle.Particularly, ethyl acetoacetate and aromatic aldehydes as agents and the need of onlysmall amount of the magnetically recoverable heterogeneous copper-based nanocatalyst makethis method low-cost, environmentally benign, and easy to use.