Synthesis of biologically active 3,8-dioxo-10-hydroxypyrano[2,3-<i>f</i>]quinoline and its reactions

Abstract

6-Aminocoumarin <b>1</b> on heating with malonic acid and phosphorousoxychloride in the presence of naphthalene gives 3<i>H</i>-7,8-dihydro-3,8-dioxo-10-hydroxypyrano[2,3,<i>f</i>]quinoline <b>2</b>. Compound <b>2</b> on further treatment with various acyclic, cyclic,aromatic, heterocyclic β-keto esters like ethyl acetoacetate, methyl salicylate, ethyl cyclopentanone-2-carboxylatc and ethyl 2,3-dihydro-3-oxobenzofuran-2-carhoxylate separately undergoes Peechman condensation to yield 3<i>H, </i>11<i>H</i>-7,8-dihydro-9-methyl-3,8,11-trioxodipyrano[2,3-<i>f</i>; 2,3-c]quinoline <b>3</b>, 3<i>H</i>-7,8,9, 10,11,12-hexahydro-3,8,12-trioxopyrano[2,3-<i>f</i> ]quinolino[3,4-<i>b</i>] pyrano[3,4-<i>a</i>] cyclopentane <b>4</b>. 3<i>H</i>,<i> </i>13<i>H</i>-7,8-dihydro-3,8, 13 trioxopyrano[2,3-<i>f</i> ]quinolino[3,4-<i>b</i>]-[1]-benzopyran <b>5</b>. and 3<i>H</i>,<i> </i>14<i>H</i>-7,8-dihydro-3,8, 14 trioxopyrano[2,3-<i>f</i> ]quinolino[3,4-<i>b</i>] -pyrano[3,4-<i>b</i>]-[1]-benzopyran <b>6</b><i> </i>respectively. Also the reaction of isatin, malononitrile and the compound <b>2</b> affords the corresponding spiro-[3<i>H</i>-indol-(1<i>H</i>, 2<i> H</i>)-3,9-((3<i>H</i>,7<i>H</i>,8<i>H</i>)-dipyrano[2,3-<i>f</i>; 2,3-c]quinoline]-11-amino-10-cyano-2,3,8-trione <b>7</b>. The structures of all the compounds have been confirmed on the basis of spectral and analytical data. The above compounds have been screened for their antimicrobial activities and arc found to possess significant antibacterial and antifungal activities.