Gold(I) Catalysis Applied to the Stereoselective Synthesis of Indeno[2,1‑b]thiochromene Derivatives and Seleno Analogues

A gold­(I)-catalyzed cascade reaction for the stereoselective synthesis of sulfur- or selenium-containing indeno­[1,2-b]­chromene derivatives from o-(alkynyl)­styrenes substituted at the triple bond with a thio- or seleno-aryl group is described. The reaction involves a double cyclization process through a proposed key gold–cyclopropyl carbene intermediate that evolves by the intramolecular addition of an aromatic to the cyclopropane ring, affording polycyclic structures. The enantioselective version was studied using gold­(I) complexes bearing chiral ligands.