AlCl3-Promoted Highly Regio- and Diastereoselective [3 + 2] Cycloadditions of Activated Cyclopropanes and Aromatic Aldehydes: Construction of 2,5-Diaryl-3,3,4-trisubstituted Tetrahydrofurans

The AlCl3-catalyzed [3 + 2] cycloaddition reaction of diethyl trans-2,3-disubstituted cyclopropane-1,1-dicarboxylates and aromatic aldehydes was carried out under mild conditions to provide a series of diethyl 2,5-diaryl-4-benzoyltetrahydrofuran-3,3-dicarboxylates in moderate to good yields with excellent diastereoselectivities. While common 2,5-cis products were obtained with electron-neutral or electron-poor aryl aldehydes, the much less common 2,5-trans products were obtained in excellent diastereoselectivities when electron-rich aryl aldehydes were used. The relative configurations of those typical products were confirmed by X-ray crystallographic analyses.