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.