Synthesis of (2-Arylethylidene)cyclobutanes by Palladium-Catalyzed Reactions of Aryl Halides with Homoallyl Alcohols Bearing a Trimethylene Group at the Allylic Position

Treatment of aryl bromides with homoallyl alcohols bearing a trimethylene group at the allylic position in the presence of cesium carbonate under palladium catalysis affords (2-aryl­ethylidene)cyclobutanes selectively. The selective formation of the alkylidenecyclobutane skeleton results from regiospecific retro-­allylation of the homoallyl alcohols, which accompanies the transposition of the double bonds.