European J Org Chem. 2021 Dec 14;2021(46):6250-6253. doi: 10.1002/ejoc.202100879. Epub 2021 Aug 25.
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 E/Z mixtures at the double bond, with the Z isomer being preferred.