title: Design of binaphthyl-modified symmetrical chiral phase-transfer catalysts: substituent effect of 4,4',6,6'-positions of binaphthyl rings in the asymmetric alkylation of a glycine derivative.
abstract: A series of symmetrical chiral phase-transfer catalysts with 4,4',6,6'-tetrasubstituted binaphthyl units have been designed, and these aryl- and trialkylsilyl-substituted phase-transfer catalysts, which included a highly fluorinated catalyst, were prepared. The chiral efficiency of these chiral phase-transfer catalysts was investigated in the asymmetric alkylation of tert-butylglycinate-benzophenone Schiff base under mild phase-transfer conditions, and the eminent substituent effect of the 4,4',6,6'-positions of the binaphthyl units on enantioselection was observed. In particular, the OctMe2Si-substituted catalyst was found to be highly efficient for the phase-transfer alkylation of tert-butylglycinate-benzophenone Schiff base with various alkyl halides, including sec-alkyl halides. The highly fluorinated catalyst was also utilized as a recyclable chiral phase-transfer catalyst by simple extraction with fluorous solvents.
authors: Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
authors: Seiji
authors: S
authors: Shirakawa
authors: Mitsuhiro
authors: M
authors: Ueda
authors: Youhei
authors: Y
authors: Tanaka
authors: Takuya
authors: T
authors: Hashimoto
authors: Keiji
authors: K
authors: Maruoka