L-Proline as an efficient catalyst for synthesis of N-heterocyclic chalcones as potential antibacterial agents

Abstract

The condensation of 4-hydroxy-3-acetyl-1<i style="">H</i>-quinoline-2-one <b style="">1</b> and substitutedbenzaldehydes <b style="">2a-i</b> in DMSO solution at room temperature yields quinolone chalcone derivatives <b style="">3a-i</b>. l-Proline has been found to be an efficient catalyst for this condensation between <b style="">1</b> and <b style="">2</b>. Only 5 mol% of the catalyst is necessary to achieve good yields of the products. Reactions proceed smoothly with variations of the substituents. <b style="">1 </b>itself is synthesized by the acylation of commercially available methyl anthranilate <b style="">4</b> with acetoacetic ester <b style="">5</b> in refluxing xylene and subsequent Dieckman intramolcular cyclization of the intermediary 2-methoxycarbonylanilide <b style="">6</b>.