Synthesis of novel pyrano[3,2-c]quinoline-2,5-diones using an acidic ionic liquid catalyst

The synthesis of novel 4-substituted-3,4-dihydro-6H-pyrano[3,2-c]quinoline-2,5-diones was accomplished efficiently via a three-component reaction between 4-hydroxyquinoline-2-one, Meldrum's acid, and an alkyl or arylaldehyde under catalysis by [Bmim]HSO4. The ionic liquid catalyst offers the advantage of realizing the synthesis of the title products at ambient temperature and widens the scope of the reactants to include aliphatic aldehydes with respect to the catalysts already applied for similar syntheses.