A new strategy for synthesis of 9-benzoyl-4-methylpyrano[2,3-f]chromene-2,8-dione using L-proline as a novel and efficient catalyst

Abstract

We report the high yield synthesis of novel 9-benzoyl-4-methylpyrano[2,3-f]chromene-2,8-dione derivatives obtained by the reaction of 8-formyl-7-hydroxy-4-methylcoumarin with various active methylene compounds. A mechanism of the tandem Knoevenagel condensation and cyclisation reaction is proposed. Structures of all compounds were elucidated on the basis of ¹H and ¹³C NMR, and mass spectrometry, and elemental analysis.