Torquoselective Nazarov Cyclization Mediated by a Chiral Sulfoxide: First Enantioselective Synthesis of two Known Anticancer Agents

In this study we describe a Nazarov cyclization of activated dienones bearing an aromatic moiety as EDG and a chiral sulfoxide group both as an EWG and a chiral inductor. The sulfinyl group directed the torquoselectivity, and AlCl3 was used as a promoter. Only both trans stereoisomers were observed. Substrates bearing activated aromatic moieties including phenyl and aromatic heterocycles led to the desired cyclopentanones. The potential of this methodology was highlighted by the first enantioselective synthesis of two anticancer agents.