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(1 H )‐one 1b , which were obtained by condensation of aromatic amines with diethyl malonate. 9‐Fluoro‐6 H ‐pyrano[3,2‐ c ]quinoline‐2,5‐dione 3b and 6 H ‐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‐2 H ‐pyrano[3,2‐ c ]quinolin‐2‐one 4a and 5‐chloro‐9‐fluoro‐2 H ‐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.