DFT Study of a 5-endo-trig-Type Cyclization of 3-Alkenoic Acids by Using Pd–Spiro-bis(isoxazoline) as Catalyst: Importance of the Rigid Spiro Framework for Both Selectivity and Reactivity

Authors

  • Dr. Randa K. Gabr,

    1. The Institute of Scientific and Industrial Research (ISIR), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan), Fax: (+81) 6-6879-8469
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  • Prof. Dr. Takuji Hatakeyama,

    1. International Research Center for Elements Science, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan), Fax: (+81) 7-7438-3186
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  • Prof. Dr. Kazuhiro Takenaka,

    1. The Institute of Scientific and Industrial Research (ISIR), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan), Fax: (+81) 6-6879-8469
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  • Prof. Dr. Shinobu Takizawa,

    1. The Institute of Scientific and Industrial Research (ISIR), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan), Fax: (+81) 6-6879-8469
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  • Yoshihiro Okada,

    1. International Research Center for Elements Science, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan), Fax: (+81) 7-7438-3186
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  • Prof. Dr. Masaharu Nakamura,

    Corresponding author
    1. International Research Center for Elements Science, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan), Fax: (+81) 7-7438-3186
    • Masaharu Nakamura, International Research Center for Elements Science, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan), Fax: (+81) 7-7438-3186

      Hiroaki Sasai, The Institute of Scientific and Industrial Research (ISIR), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan), Fax: (+81) 6-6879-8469

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  • Prof. Dr. Hiroaki Sasai

    Corresponding author
    1. The Institute of Scientific and Industrial Research (ISIR), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan), Fax: (+81) 6-6879-8469
    • Masaharu Nakamura, International Research Center for Elements Science, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan), Fax: (+81) 7-7438-3186

      Hiroaki Sasai, The Institute of Scientific and Industrial Research (ISIR), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan), Fax: (+81) 6-6879-8469

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Abstract

The reaction pathway of an enantioselective 5-endo-trig-type cyclization of 3-alkenoic acids catalyzed by a chiral palladium–spiro-bis(isoxazoline) complex, Pd–SPRIX, has been studied by density functional theory calculations. The most plausible pathway involves intramolecular nucleophilic attack of the carboxylate moiety on the C[DOUBLE BOND]C double bond activated by Pd–SPRIX and β-H elimination from the resulting organopalladium intermediate. The enantioselectivity was determined in the cyclization step through the formation of a π-olefin complex, in which one of the two enantiofaces of the olefin moiety was selected. The β-H elimination occurs via a seven-membered cyclic structure in which the acetate ligand plays a key role in lowering the activation barrier of the transition state. In the elimination step, the SPRIX ligand was found to behave as a monodentate ligand due to the hemilability of one of the isoxazoline units thereby facilitating the elimination. Natural population analysis of this pathway showed that the more weakly electron-donating SPRIX ligand, compared with the bis(oxazoline) ligand, BOX, facilitated the formation of the π-olefin complex intermediate, leading to a smaller overall activation energy and a higher reactivity of the Pd–SPRIX catalyst.

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