New 1,5-dicarbonyl compounds were prepared, as versatile precursors to pyridine derivatives, by a tandem Claisen-Schmidt condensation/ Michael addition reaction, that is condensation between 5-chloro-3-methyl-1-phenyl-1Hpyrazole- 4-carbaldehyde and acetophenones, and the formed adduct then reacts with a second molecule of acetophenone. The preparation of substituted pyridines was achieved using NH4OAc as nitrogen source under solvent-free microwave irradiation.

A series of pyrimido[4,5-b]quinolines (5-deazaflavines), were synthesized by microwave assisted intramolecular cyclization. The N⁴-substituted-2,4-diamino-6-chloro-pyrimidine-5-carbaldehydes, were prepared by selective monoamination of 2-amino-4,6-dichloropyrimidine-5-carbaldehyde with aliphatic and aromatic amines.

A series of 5-aryl-2-methylthio-5,12-dihydrobenzo[g]pyrimido[4,5-b]quinoline-4,6,11(3H)-trione was synthesized through an environmental friendly multicomponent methodology and characterized with FT-IR (Fourier Transform infrared spectroscopy), ¹H NMR (Nuclear Magnetic Resonance ), ¹³C NMR and GC-MS (gas chromatography-mass spectrometry). The 5-(4-methoxyphenyl)-2-methylthio-5,12-dihydrobenzo[g]pyrimido[4,5-b]quinoline-4,6,11(3H)-trione 4c compound was characterized by X-ray single crystal diffraction. The geometry of 4c has been fully optimized using DFT (Density functional theory), B3LYP functional and 6-31G(d,p) basis set, thus establishing the ground state energy and thermodynamic features for the mentioned compound, which are in accordance with the experimental data and the crystal structure. The experimental results reveal a strong preference for the regioselective formation of 4c linear four fused rings over the angular four fused and suggest a possible kinetic control in product formation.