An efficient synthesis of 4-alkyl-4-methyl-3,4-dihydro-2H,5H-pyrano[3,2-c]chromene-2,5-dione or 4-aryl-3,4-dihydro-2H,5H-pyrano[3,2-c]chromene-2,5-diones via reaction 4-hydroxycoumarin with Meldrum's acid and ketones or aldehydes is described.
Three- component reactions of 1-(6-hydroxy-2-isopropenyl-1-benzofuran-yl)-1-ethanone,
aldehydes and malononitrile or ethyl cyanoacetate in the presence of nanoparticles of ZnO as catalyst are explained as
effective and green synthetic method for generating 9H- furo[2,3-f]chromenes in good yield.