The Role of the Counterion and of Silicon Chelation in the Selective Mono(trifluoromethylation) of Tartaric Acid Derived 1,4-Diketones

Authors

  • Dr. Dominique Harakat,

    1. Institut de Chimie Moléculaire de Reims (UMR 6229), Université de Reims Champagne-Ardenne - CNRS, UFR Sciences, BP 1039, 51687 REIMS Cedex 2 (France), Fax: (+33) 326-91-31-66
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  • Dr. Fabien Massicot,

    1. Institut de Chimie Moléculaire de Reims (UMR 6229), Université de Reims Champagne-Ardenne - CNRS, UFR Sciences, BP 1039, 51687 REIMS Cedex 2 (France), Fax: (+33) 326-91-31-66
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  • Dr. Jean Nonnenmacher,

    1. Institut de Chimie Moléculaire de Reims (UMR 6229), Université de Reims Champagne-Ardenne - CNRS, UFR Sciences, BP 1039, 51687 REIMS Cedex 2 (France), Fax: (+33) 326-91-31-66
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  • Dr. Fabienne Grellepois,

    1. Institut de Chimie Moléculaire de Reims (UMR 6229), Université de Reims Champagne-Ardenne - CNRS, UFR Sciences, BP 1039, 51687 REIMS Cedex 2 (France), Fax: (+33) 326-91-31-66
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  • Prof. Charles Portella

    Corresponding author
    1. Institut de Chimie Moléculaire de Reims (UMR 6229), Université de Reims Champagne-Ardenne - CNRS, UFR Sciences, BP 1039, 51687 REIMS Cedex 2 (France), Fax: (+33) 326-91-31-66
    • Institut de Chimie Moléculaire de Reims (UMR 6229), Université de Reims Champagne-Ardenne - CNRS, UFR Sciences, BP 1039, 51687 REIMS Cedex 2 (France), Fax: (+33) 326-91-31-66
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Abstract

The addition of trifluoromethyl(trimethyl)silane (TFMTMS) to tartaric acid derived aromatic 1,4-diketones was reported to be highly stereoselective but also chemoselective towards a monoaddition product. This chemoselectivity remained unexplained. Complementary experiments and monitoring of the reaction by electrospray ionization mass spectrometry (ESI-MS) show that: i) the countercation (tetrabutylammonium (TBA+) or Cs+) associated to the initiator and the charged intermediates in the chain reaction plays a crucial role and ii) in the case of a tetrabutylammonium salt initiator, the second addition on the preformed monoadduct does occur but the resulting bis(trifluoromethyl)carbinolate is unable to evolve through the chain-transfer process and it exhibits an intramolecular Si[BOND]O interaction.

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