Preparation of 4-Hydroxy-3-Substituted, 2H-1-Benzopyran-2-ones and 2H-1-Benzothiopyran-2-ones from Carboxylic Esters and Methyl Salicylates or Methyl Thiosalicylate

Article abstract of DOI:10.1002/jhet.5570340411

C(α)-Carboxylic acid esters were treated with excess lithium diisopropylamide, condensed with methyl salicylates or methyl thiosalicylate, followed by acid cyclization to either 4-hydroxy-3-substituted, 2H-1-benzopyran-2-ones (coumarins), or 2H-1-benzothiopyran-2-ones (thiocoumarins).