Synthesis of New Pyrano-fused Quinolines as Antibacterial and Antimicrobial Agents

This manuscript describes a brief overview of latest research involving the use of pyrano-fused quinolines as new antibacterial and antimicrobial agents. The synthesis begins with 4-hydroxy quinolone-2-one 1a and 6-fluoro-4-hydroxyquinolin-2(1H)-one 1b, which were obtained by condensation of aromatic amines with diethyl malonate. 9-Fluoro-6H-pyrano[3,2-c]quinoline-2,5-dione 3b and 6H-pyrano[3,2-c]quinoline-2,5-dione 3a were obtained by reaction with diethyl malonate in presence of ammonium acetate. These pyranoquinolones on refluxing in phosphorous oxychloride were converted to 5-chloro-2H-pyrano[3,2-c]quinolin-2-one 4a and 5-chloro-9-fluoro-2H-pyrano[3,2-c]quinolin-2-one 4b in good yields. The chloro functionality in compound 4a and 4b, which are reactive, can be replaced by various nucleophilic reagents such as amines and amino acids. The resulted amino pyrano[3,2-c] quinolines showed moderate-to-excellent antibacterial and antimicrobial activity.