Lewis‐Acid‐Catalyzed (3+2)‐Cycloadditions of Donor‐Acceptor Cyclopropanes with Thioketenes

Abstract

The reactivity of donor-acceptor (D-A) cyclopropanes towards thioketenes was investigated. In a (3+2)-cycloaddition using Sc(OTf)₃ as a Lewis acidic catalyst, the corresponding exocyclic thioenol ethers (2-methylidene tetrahydrothiophenes) were formed in moderate to good yields. Unsymmetrical thioketenes provided <i>E</i>/<i>Z</i> mixtures at the double bond, with the <i>Z</i> isomer being preferred.