Ionic Liquid Mediated Green Synthesis of Spirooxindoles from N-methyl Quinolones and Their Anti Bacterial Activity

Three-component reaction involving condensation of 1-methyl quinoline-2,4(1H,3H)-dione 1, isatins 2(a–e), and malononitrile/cyanoacetic ester 3(a–b) in the task-specific ionic liquid [DBU][Ac] (1,8-diazabicyclo[5.4.0]-undec-7-en-8-ium acetate) leading to the spirooxindole derivatives 4(a–j) is described. This approach is affords the products in high yields without use of column chromatography and resulting compounds were evaluated for antibacterial activity against both gram positive and gram negative bacteria (Staphylococcus aureus, Escherichia coli, Bacillus cereus, Bacillus subtilis, Salmonella typhimurium, and Klebsiella pneumonia). Among the all compounds, four compounds, that is, 4b, 4e, 4f, 4g, 4j exhibited moderate activity against all the strains as compared with the standard used.