A Green Approach for the Synthesis of Novel 7,11-Dihydro-6H-chromeno[3,4-e]isoxazolo[5,4-b]pyridin-6-one Derivatives Using Acidic Ionic Liquid [C4mim][HSO4]

A multicomponent reaction capable of affording a wide range of novel 7,11-dihydro-6H-chromeno[3,4-e]isoxazolo[5,4-b]pyridin-6-one derivatives via one-pot three-component condensation of 4-hydroxycoumarin, aromatic aldehydes, and 5-amino-3-methylisoxazole in ionic liquid 1-butyl-3-methylimidazolium hydrogen sulfate ([C4mim][HSO4]) is reported. Structures have been confirmed by spectral and X-ray studies. Crystal packing of 4b has also been reported. Green solvent, short reaction time, easy workup, and high yields are the salient features of the present protocol.