Coumarins and related compounds. Part IV. Aluminium chloride-catalysed reaction of phenols with methyl acrylate: a new approach to the synthesis of hydroxycoumarins

Abstract

The synthesis of 5-,6- and 7-hydroxycoumarins by dehydrogenation of the corresponding 3,4-dihydro-derivatives obtained by aluminium chloride-catalysed reaction of dihydric phenols or their derivatives with methyl acrylate is reported. The compound previously described as 5-hydroxydihydrocoumarin has been proved to be 3,4,6,7-tetrahydrobenzo[1,2-b: 5,4-b′]dipyran-2,8-dione on the basis of spectral evidence and synthesis.