A new and efficient synthesis of coumestan and coumestrol

Article abstract of DOI:10.1055/s-1990-26882

4-Aryloxy-3-iodocoumarins (4-aryloxy-3-iodo-2H-1-benzopyran-2-one), 4a-c, which are readily available by known procedures starting from 4-hydroxycoumarins 1 a,b and diacetoxyiodobenzenes 2a-c; are cyclized with palladium chloride in triethylamine to yield the coumestanes (6H-benzofuran[3,2-c][1]benzopyran-6-ones) 5a-c.