A microwave-assisted synthesis of 3,4-dihydro-pyrimidin-2-(1H)-ones catalyzed by FeCl3-supported Nanopore Silica under solvent-free conditions

Lewis acid supported Nanopore Silica catalysts for microwave-assisted Biginelli reaction under solvent-free conditions were prepared by impregnating FeCl3 dissolved in ethanol to Nanopore Silica at 40 degrees C. Biginelli reaction under solvent-free conditions, one-pot three-component condensation of urea, benzaldehyde, and ethyl acetoacetate, catalyzed with porous material or Lewis acid supported porous material, such as MCM-41, SBA-15, VSB-5, Nanopore Silica, FeCl3/MCM-41, FeCl3/Nanopore Silica, CeCl3/Nanopore Silica and InCl3/Nanopore Silica, was investigated. Our recent results of the microwave-assisted Biginell reaction of some benzaldehyde derivatives starting materials using MCM-41, Nanopore Silica, FeCl3/Nanopore Silica, under solvent-free conditions are also reported. Aromatic aldehydes carrying either electron releasing or electron withdrawing substituents in the ortho, meta, and para positions afforded good yields of the products using MCM-41 as a catalyst. When Nanopore Silica was used as a catalyst, the yield of the Biginelli product was in the range of 27-56%. However FeCl3/Nanopore Silica has been employed as a catalyst, the yield of the Biginelli product was increased dramatically. Thus it has been found that the use of FeCl3/Nanopore Silica as heterogeneous catalyst has made this method very cost effective. (C) 2008 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.