A gem-Dibromocyclopropane Ring-Expansion/Mizoroki-Heck Cyclisation Route to Tetrahydrodibenzofurans

Readily accessible, oxygenated 6,6-dibromobicyclo[3.1.0]hexanes react with isovanillin in the presence of silver salts and an inorganic base to afford ring-expanded/nucleophilic trapping products of various regio- and stereo-chemical forms. Most such products undergo efficient, intramolecular Mizoroki-Heck reactions to give the corresponding tetrahydrodibenzofurans. In certain cases, simple variations in the first step of such reaction sequences enables the preparation distinct ring-expansion products that also cyclise to give tetrahydrodibenzofurans embodying alternative substitution patterns.