Coumarin Synthesis via Knoevenagel Condensation Reaction in 1,1,3,3-N,N,N′,N′′-Tetramethylguanidinium Trifluoroacetate Ionic Liquid

Coumarin derivatives were synthesized in relatively high yields via Knoevenagel condensation reaction of an ortho-hydroxyaryl aldehyde and an activated beta-dicarbonyl C-H acid in the presence of a recyclable ionic liquid 1,1,3,3-N,N,N',N'-tetramethylguanidinium trifluoroacetate under either classical heating conditions or using microwave irradiation. Application of microwave irradiation decreased the required time by a factor of about 200. The ionic liquid could be recycled several times without loss of efficiency with regards to the reaction times and yields.