Lewis Acid-Mediated Ring-Opening Reactions of trans-2-Aroyl-3-styrylcyclopropane-1,1-dicarboxylates: Access to Cyclopentenes and E,E-1,3-Dienes.

The ring-opening reaction of trans-2-aroyl-3-styrylcyclopropane-1,1-dicarboxylates was investigated with different Lewis acids. With SnCl4, the cyclopropane dicarboxylates afforded cyclopentene derivatives through ring opening followed by cyclization (vinylcyclopropane-cyclopentene rearrangement). With TiCl4, they furnished E,E-1,3-diene derivatives stereoselectively via ring opening followed by proton elimination.