Highly Diastereoselective Synthesis of Tetrahydrofurans via Lewis Acid-Catalyzed Cyclopropane/Aldehyde Cycloadditions

A one-step procedure for the preparation of 2,5-disubstituted tetrahydrofurans from donor−acceptor cyclopropanes and aldehydes has been developed. In the presence of a catalytic amount of Sn(OTf)₂, cyclopropanes bearing an aryl or conjugated donor substituent vicinal to a malonyl diester group undergo cycloadditions with diverse conjugated aldehydes furnishing tetrahydrofurans with high cis diastereoselectivity. This method is useful for the preparation of regiodefined tetrahydrofurans.