Department of Biotechnology and Life Science, Faculty of Technology, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan.
Chem Asian J. 2011 Sep 5;6(9):2463-70. doi: 10.1002/asia.201100363. Epub 2011 Jul 14.
Herein, we present details of our conformationally flexible, 1,3-diamine-tethered guanidine/bisthiourea organocatalysts for chemo-, regio-, and enantioselective 1,4-type Friedel-Crafts reactions of phenols. These organocatalysts show a unique stereo-discrimination governed by the differential activation entropy (ΔΔS(≠)), rather than by the differential activation enthalpy (ΔΔH(≠)). Extensive kinetic analyses using Eyring plots for a series of guanidine/bisthiourea organocatalysts revealed the key structural motif in the catalysts associated with a large magnitude of differential activation entropy (ΔΔS(≠)). A plausible guanidine-thiourea cooperative mechanism for the enantioselective Friedel-Crafts reaction is proposed.
在此，我们介绍了我们的构象柔性、1,3-二胺键合胍/双硫脲有机催化剂的详细信息，这些催化剂可用于酚类的化学选择性、区域选择性和对映选择性 1,4 型 F-C 反应。这些有机催化剂表现出由差分激活熵（ΔΔS(≠)）而不是由差分激活焓（ΔΔH(≠)）控制的独特立体选择性。通过对一系列胍/双硫脲有机催化剂的 Eyring 图进行广泛的动力学分析，揭示了与大的差分激活熵（ΔΔS(≠)）相关的催化剂中的关键结构模体。提出了对映选择性 F-C 反应的胍-硫脲协同作用机制的合理假设。
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