An environmentally friendly, green, and highly efficient process for the synthesis of biologically and pharmacologically 4H-benzo[b]pyrans and 3,4-dihydropyrano [c] chromenes is developed by condensing cyclic aromatic aldehydes, malononitrile, and dimedone or 4‐hydroxycoumarin in the presence of lactic acid as an efficient and green catalyst. The corresponding products have b...
