Mechanistic insights into entropy-driven 1,2-type Friedel-Crafts reaction with conformationally flexible guanidine-bisthiourea bifunctional organocatalysts

Katsuhiro Nakano, Tatsuya Orihara, Masaki Kawaguchi, Keisuke Hosoya, Shogo Hirao, Ryosuke Tsutsumi, Masahiro Yamanaka, Minami Odagi, Kazuo Nagasawa

研究成果: Article査読

3 被引用数 (Scopus)

抄録

In some asymmetric catalytic reactions, the enantio-discrimination step is dominated by the change in entropy, in contrast to the usual enthalpy-driven process, but the origin of this entropy-dependent behavior is unclear. Here, we first conducted Eyring analysis to confirm the entropy-driven character of our previously reported 1,2-type Friedel-Crafts (FC) reaction of sesamol with imine, catalyzed by conformationally flexible guanidine-bisthiourea bifunctional organocatalyst, and then we carried out computational studies to compare the transition states leading to the two enantiomers. We found no significant temperature dependence of ΔH or -TΔS for TS-R, the transition state leading to the R enantiomer. In TS-S, on the other hand, -TΔS was increased at higher temperature, although ΔH was unchanged. Furthermore, the benzyl groups of the catalyst increase the contribution of the enthalpy term to the enantioselectivity, albeit with retention of the entropy-driven behavior arising from the conformationally flexible catalyst structure.

本文言語English
論文番号132281
ジャーナルTetrahedron
92
DOI
出版ステータスPublished - 2021 7月 16
外部発表はい

ASJC Scopus subject areas

  • 生化学
  • 創薬
  • 有機化学

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