Task-Specific Ionic Liquid as the Recyclable Catalyst for the Rapid and Green Synthesis of Dihydropyrano[3,2-c]chromene Derivatives

Abstract

A task-specific ionic liquid, [H₃N⁺–CH₂–CH₂–OH][CH₃COO⁻], was successfully applied as an efficient and reusable catalyst for the one-pot domino to approach to dihydropyrano[3,2-c]chromene derivatives with atom economy in a condensation reaction of 4-hydroxycoumarin, aldehydes, and malononitrile in a combinatorial fashion. The reaction gave excellent yields within short reaction times at room temperature under solvent-free grinding conditions. The products and ionic liquid could be conveniently separated from the reaction mixture, indicating that the whole process was performed as a green chemical transformation.

Keywords:

• Dihydropyrano[3,2-c]chromene
• ionic liquid
• multicomponent reaction
• recyclable catalyst
• solvent-free

ACKNOWLEDGMENT

We are thankful to the University of Sistan and Baluchestan Research Council for the partial support of this research.

Notes

^a Yields refer to the isolated pure products. All of the desired product(s) were characterized by comparison of their physical and spectroscopic data with those of known compounds.^{[ 14 ,} 23-25 ^]

^b The spectral patterns of the new products showed similar peaks and fragmentations according to analogous compounds reported in the literature.