Cyclopentene Synthesis by a Catalytic [3+2] Annulation of Donor-Acceptor Cyclopropanes with Polarized Alkenes

[3+2] Annulation of donor-acceptor cyclopropanes with alkynes represents an efficient route to cyclopentenes. Here, we describe a new cyclopentene synthesisviaLewis acid-catalyzed ring-opening addition and intramolecular SNV reaction of donor-acceptor cyclopropanes with alkenes. The reaction is carried out under the catalysis of Sc(OTf)(3)by using polarized alkenes, namely alpha-oxo ketene dithioacetals, as 2 C partners.