Fluorolactonization of norbornenecarboxylic acids and their methyl esters with F-TEDA-BF4 and XeF2 |
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Authors: | Lyudmila F. Lourie Galina V. Shevchenko Alexander N. Chernega Eduard B. Rusanov Judith A.K. Howard |
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Affiliation: | a Institute of Organic Chemistry, National Academy of Sciences of Ukraine, 5 Murmanskaya str., 02094 Kyiv, Ukraine b Department of Chemistry, University of Durham, Science Laboratories, South Road, Durham DH1 3LE, UK |
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Abstract: | The selective fluorolactonization was achieved by treatment of cis-5-norbornene-2,3-endo-dicarboxylic acid or its monomethyl and dimethyl esters with F-TEDA-BF4 or XeF2. The reactions of 5-norbornene-endo-2-carboxylic acid and its monomethyl ester with F-TEDA-BF4 or XeF2 proceed in a non-selective manner to give fluorolactonization, addition and rearrangement products. The basic factor responsible for selectivity of the fluorolactonization is the presence of two endo-oriented carboxyl groups in the substrate molecule. The electrophilicity and type of the fluorinating agent is of secondary importance in this regard. It is postulated that the fluorolactonization of norbornenecarboxylic acids and their methyl esters with F-TEDA-BF4 or XeF2 is realized mainly via “open” fluoronorbornyl carbocation intermediates which in the reaction with XeF2 are postulated as the tight ion pairs. |
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Keywords: | Fluorolactonization Norbornenecarboxylic acids Selectivity Fluorocarbocations |
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