nanocrystalline tio2 as an efficient and reusable catalyst for the one-pot synthesis of polyhydroquinolien derivatives via hantzsch reaction

an efficient synthesis of polyhydroquinoline derivatives was reported via four-component coupling reactions of aldehydes, 1,3-dicarbonyl ketones (dimedone or 1,3-cyclohexanedione), ethyl acetoacetate or methyl acetoacetate and ammonium acetate in the presence of a catalytic amount of nanocrystalline tio2 under solvent free conditions. the reported method is mild, rapid and has the advantages such as heterogeneous catalysis, simple work-up procedure, recyclability of the catalyst and purification of products without chromatographic methods.