Asian Journal of Research in Chemistry

Reactions of acetyl acetone to aromatic amines have been carried out in presence of p-toluenesulphonic acid and molecular sieves by a new microwave irradiation assisted procedure to generate N-aryl enaminoketones. Two stereoisomeric enaminoketones, viz. cis and trans enaminoketones, are formed as intermediates which are characterized by NMR studies. Computations are performed at the DFT/B3LYP/6–311++G(2d, p) level to analyze the course of these reactions. The computed GIAO nuclear magnetic shielding tensors and experimental data are found to be in good agreement to each other in case of both cis and trans enaminoketones. Transition states and intermediates for the generation of cis and trans enaminoketones are successfully located at DFT/B3LYP/6311++G(2d, p) level of theory and the relative energies are calculated to rationalize the selectivity of the process. Two transition states and one intermediate are located for both cis and trans pathways. The enaminoketones are subsequently converted to quinolines under acid catalysis with 80% sulphuric acid under microwave irradiation in high yields. This method is a significant improvement on the conventional methods for preparation of substituted quinolines from 1, 3-diketones, particularly in view of very short times taken, the cleanness of the reactions and high yields. The present theoretical study of the reaction course at DFT/B3LYP/6–311++G(2d, p) level is the first contribution to computational calculations of such reactions.