Double Thiol-Chiral Brønsted Base Catalysis: Asymmetric Cross Rauhut-Currier Reaction and Sequential [4 + 2] Annulation for Assembly of Different Activated Olefins.

A double catalytic system combining 2-mercaptobenzoic acid and a chiral phase transfer substance was disclosed for the intermolecular cross Rauhut-Currier reaction of 2-cyclopentenone and isatin-based alkylidene malononitriles. The resulting chiral adducts were sequentially assembled with diverse electron-deficient olefins to furnish highly enantioenriched cyclohexane derivatives (up to 96:4 er, >19:1 dr). A similar catalytic system of 2-mercaptobenzoic acid and quinine was further developed for the reaction of 2-cyclopentenone and alpha-cyano chalcones (up to 96.5:3.5 er).