title: Enantioselective synthesis of 3,4-dihydropyran-2-ones by domino Michael addition and lactonization with new asymmetric organocatalysts: cinchona-alkaloid-derived chiral quaternary ammonium phenoxides.
abstract: Chiral quaternary ammonium phenoxides were readily prepared from commercially available cinchona alkaloids and proved to be useful new asymmetric organocatalysts. Among various chiral quaternary ammonium phenoxides, a cinchonidine-derived catalyst that bears both a sterically hindered N1-9-anthracenylmethyl group and a strongly electron withdrawing 9-O-3,5-bis(trifluoromethyl)benzyl group were found to be highly effective for the Michael addition of ketene silyl acetals (derived from phenyl carboxylates) and alpha,beta-unsaturated ketones followed by lactonization. Optically active 3,4-dihydropyran-2-one derivatives were obtained in high yields with excellent control of enantio- and diastereoselectivity. This catalyst can be handled in air and stored at room temperature in a sealed bottle without decomposition for at least one month.
authors: The Kitasato Institute, Center for Basic Research, 6-15-5 (TCI) Toshima, Kita-ku, Tokyo 114-0003, Japan.
authors: Takashi
authors: T
authors: Tozawa
authors: Hitoshi
authors: H
authors: Nagao
authors: Yoshinobu
authors: Y
authors: Yamane
authors: Teruaki
authors: T
authors: Mukaiyama
mesh_terms: D002384:Catalysis; D002929:Cinchona / Q000737:chemistry*; D002930:Cinchona Alkaloids / Q000737:chemistry*; D007783:Lactones / Q000737:chemistry*; D015394:Molecular Structure; D010087:Oxides / Q000737:chemistry*; D011714:Pyrans / Q000138:chemical synthesis* / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D002930:Cinchona Alkaloids; D007783:Lactones; D010087:Oxides; D011714:Pyrans; D000644:Quaternary Ammonium Compounds