An efficient synthesis of 4H-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(1H)-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.