Pyridopyrimidines represent a highly important class of compounds which exhibit a wide
spectrum of biological properties. Nanoscale metal oxide catalysts have been extensively studied for
their application in organic reactions owing to their special features such as high surface area and pore
sizes as supports. Titanium dioxide nanoparticles (TiO2 NPs) are an attractive candidate for readily
available cheap nanocatalysts, due to their unique properties such as being non-toxic, moisture stable
and reusable catalyst. 7-amino-2,4-dioxo-5-aryl-1,2,3,4-tetrahydropyrido[2,3-d]pyrimidine-6-carbonitriles
were synthesized through the reaction of 4(6)-aminouracil, aromatic aldehydes, and malononitrile using
calcined TiO2-SiO2 nanocomposite as a reusable catalyst in water at ambient temperature. All the
synthesized compounds were well characterized by their elemental analyses, IR, 1H and 13C NMR
spectroscopy. The synthesized catalyst was fully characterized by the powder X-ray diffraction (XRD),
the scanning electron microcopy (SEM), the transmission electron microscopy (TEM), and the x-ray
fluorescence (XRF) techniques. The reaction proceeded through calcined TiO2-SiO2 nanocomposite
catalyzed three-component reaction affording twelve target compounds in high yields. This method
introduced a novel protocol to provide 7-amino-2,4-dioxo-5-aryl-1,2,3,4-tetrahydropyrido[2,3-
d]pyrimidine-6-carbonitrile derivatives and offer several advantages like very simple operation, using
inexpensive, recyclable and non-toxic catalyst, mild reaction conditions, high yields of products (92-
98%), short reaction times (2.5-4 h), and green aspects by avoiding toxic catalysts and hazardous solvents.
Silica-based sulfonic acid (MCM-41-SO3H): a practical and efficient catalyst for the synthesis of highly substituted quinolines under solvent-free conditions at ambient temperature