Lewis Acid Catalyzed [3+2] Annulations of γ‐Butyrolactam‐Fused Donor–Acceptor Cyclopropanes with Aromatic Aldehydes and Aldimines

A series of gamma-butyrolactam fused donor-acceptor (D-A) cyclopropanes were synthesized, and their reactivities in Lewis acid catalyzed [3+2] annulations with aromatic aldehydes and aldimines were studied. A range of gamma-butyrolactam fused tetrahydrofurans and gamma-butyrolactam fused pyrrolidines containing four contiguous stereogenic centers were generated in good-to-excellent yields and with exclusive diastereoselectivities and high enantiospecificity under the catalysis of 1 mol-% of Al(OTf)(3).