An efficient synthesis of 4 H -pyrano quinolinone derivatives catalysed by a versatile organocatalyst tetra- n -butylammonium fluoride and their pharmacological screening

A new series of indole-based pyranoquinoline derivatives P 1–24 has been synthesized by a one-pot cyclocondensation reaction of 2-(4-substituted)phenyl- N -allyl-indole-3-carbaldehydes 1a–d ; active methylenes 2a–c ; and 4-hydroxy-1-substituted quinolin-2(1 H )-one 3a–b catalysed by an organocatalyst tetra- n -butylammonium fluoride (TBAF) in aqueous ethanol. The easy experimental procedure of the reaction leads to excellent yields of pyranoquinoline derivatives. All the compounds were screened against a representative panel of bacteria and fungi. Some of the compounds are found to be equipotent or more potent than standard drugs as evident from the structural activity relationship study.