Synthesis of Cyclopentadiene-Fused Chromanones via One-Pot Multicomponent Reactions

We have developed one-pot method for the synthesis of functionalized novel cyclopentadiene-fused chromanone scaffolds. A variety of 4-oxo-2,4-dihydro­cyclopenta­[c]­chromene-1,2-dicarboxylates were obtained in moderate to good yields via condensation of 2-hydroxybenzaldehydes and ethyl acetoacetate with 1:1 acetylenecarboxylate–isocyanides in toluene. These reactions presumably proceed via reaction of the in situ generated 3-acetyl-2H-chromen-2-ones with acetylenecarboxylate–isocyanide zwitterionic intermediates through Michael addition/intramolecular cyclization and double [1,5] acyl shift rearrangement cascade.