Synthesis of pyrrole-fused chromanones via one-pot multicomponent reactions

We have developed one-pot method for the synthesis of functionalized novel pyrrole-fused chromanones. A variety of 5-hydroxy-N-substituted-2H-dihydrochromeno[3,4-c]pyrrole-2-ones were obtained in moderate to good yields via condensation of 2-hydroxybenzaldehydes and ethyl acetoacetate with isocyanides in ethanol. The proof of the structure relies on analytical investigation and X-ray crystallography. These reactions presumably proceed via reaction of the in situ generated 3-acetyl-2H-chromen-2-one intermediates with isocyanides through Michael addition/intramolecular cyclization/oxidation tandem sequences.