A novel synthetic approach for the synthesis of pyrano[3,2-c] quinolone-3carbaldehydes by using modified Vilsmeier Haack reaction, as potent antimicrobial agents

Abstract This research work is about the synthesis of pyranoquinolone-3carbaldehydes, heterocyclic compounds which were constructed by modifying Vilsmeier-Haack reaction. A leading approach towards green chemistry and successful methodology was devised during this research project for the synthesis of various pyranoquinolone-3-carbaldehydes at low temperature. Some workers reported the synthesis of chromones and chloroquinoline-3carbaldehydes. Interesting aspect of the present work was to successfully utilize two methodologies during a single reaction (one to cyclize a pyran ring and second to insert formyl group) by manipulating the different functional groups attached to the reactants and to construct the desired molecules. In some works, cited during the formylation reaction by using Vilsmeier Haack reagent, halogenated products were reported while in this synthetic study the final products were formylated but nonhalogenated. This methodology is a milestone for the construction of an aldehyde functional group on some parent moieties. The reaction is an example of one pot synthesis. All synthesized compounds were found having several pharmacological characteristics. These derivatives were characterized by FTIR, 1 HNMR, EIMS and elemental (C, H and N) analyses; confirming the synthesis of the labelled products. The reactants used in this research project were synthesized by Gould Jacobs reaction prepared during our last research project as cited [26]. The antibacterial activity of ligands and metal complexes was determined by disc diffusion method using Bacillus subtilis , Escherichia coli , and Staphylococcus aureus and got excellent results.