Stereospecific Reactions of Donor–Acceptor Cyclopropanes with Thioketones: Access to Highly Substituted Tetrahydrothiophenes

Lewis‐acid‐catalyzed reactions of 2‐substituted cyclopropane 1,1‐dicarboxylates with thioketones are described. Highly substituted tetrahydrothiophenes with two adjacent quaternary carbon atoms were obtained in a stereospecific manner under mild conditions and in high yield when using AlCl3 as Lewis acid. Moreover, an intramolecular approach was successfully implemented to gain access to sulfur‐bridged [n.2.1] bicyclic ring systems. Conversion of selenoketones, the heavier analogues, under similar conditions resulted in the formation of various tetrahydroselenophenes. Thiocarbonyl Insertion: Donor–Acceptor cyclopropanes undergo a formal [3+2] cycloaddition with thioketones under AlCl3 catalysis and mild conditions to yield highly substituted tetrahydrothiophenes. An intramolecular variant led to bicyclic products. Similar cycloadditions with bisarylselenoketones were also achieved.