title: Chiral Tertiary Sulfonium Salts as Effective Catalysts for Asymmetric Base-Free Neutral Phase-Transfer Reactions.
abstract: Although chiral quaternary ammonium and phosphonium salts are commonly used for asymmetric organocatalysis, the catalytic ability of chiral tertiary sulfonium salts has yet to be demonstrated in asymmetric synthesis. Herein, we show that chiral bifunctional trialkylsulfonium salts catalyze highly enantioselective conjugate additions of 3-substituted oxindoles to maleimides under base-free neutral phase-transfer conditions.
authors.affiliation: Department of Environmental Science, Graduate School of Fisheries and Environmental Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki, 852-8521, Japan.
authors.forename: Shiyao
authors.initials: S
authors.lastname: Liu
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto, 606-8502, Japan.
authors.forename: Keiji
authors.initials: K
authors.lastname: Maruoka
authors.affiliation: Department of Environmental Science, Graduate School of Fisheries and Environmental Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki, 852-8521, Japan.
authors.forename: Seiji
authors.identifier: 0000-0003-1027-8922
authors.initials: S
authors.lastname: Shirakawa
keywords: asymmetric catalysis; ion pairs; organocatalysis; phase-transfer catalysis; sulfur