A New Short Way to Furocoumarins

Abstract

The Fries rearrangement of hydroxycoumarin chloroacetates provides a new short way to furocoumarins. 7-Hydroxycoumarin chloroacetates have been transformed in the presence of AICI3 into the proper dihydrofuro[2,3-h]coumarin-9-ones in high yields. 8-Substituted-7-hydroxycoumarin chloroacetates undergo into dihydrofuro[2,3-g]coumarin-6-ones in the presence of A1C13. 4-Hydroxycoumarin chloroacetate has been transformed into the dihydrofuro[2,3-c]coumarin-3-one in the same conditions. Reduction of all dihydrofurocoumarinones followed by dehydration provide the proper furocoumarins in good yields. This new way to furocoumarins is mostly suitable for angelicin derivatives synthesis. All new coumarin derivatives have been characterised by NMR and mass spectra.