Natural benzofurans: synthesis of the arylbenzofuran constituents of Sophora tomentosa

The structure, 2-(2′,4′-dihydroxyphenyl)-5,6-methylenedioxybenzofuran (1), suggested for Sophora compound I has been confirmed by a synthesis in which the benzofuran heterocycle was constructed by an intramolecular Wittig reaction of an o-bromomethylphenyl aroyl ester. The congeneric Sophora compound II, 2-(2′-hydroxy-4′-methoxyphenyl)-5,6-methylenedioxybenzofuran (2) was synthesized by formation of the benzofuran via the reaction of a copper(I) arylacetylide with an o-iodophenyl ester.