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  • 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.
    Author: Shirakawa S, Ueda M, Tanaka Y, Hashimoto T, Maruoka K.
    Journal: Chem Asian J; 2007 Oct 01; 2(10):1276-81. PubMed ID: 17705320.
    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.
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