Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P. R. China.
Chemistry. 2019 Mar 12;25(15):3740-3751. doi: 10.1002/chem.201803752. Epub 2019 Jan 11.
Quaternary ammonium salts play an important role in asymmetric catalysis. In this Minireview, how asymmetric ion-pairing catalysis with ammonium ions has been utilized in organic synthesis is explained, particularly in the design of novel catalytic cycles. This includes the use of chiral ammonium-based catalysts for the construction of challenging stereogenic centers. Ammonium-derived electrophilic reagents, typically formed in situ and in the context of phase-transfer catalysis (PTC), have also been utilized in asymmetric bond-forming reactions. Furthermore, ammonium salts have been employed as substrates in several stereocontrolled C-N bond cleavage processes, leading to enantioenriched products by using novel asymmetric induction modes. In addition, merging ammonium ion-pairing catalysis with other catalytic approaches has also emerged as a new platform for achieving previously less straightforward reactions, thereby allowing new synthetic applications.
季铵盐在不对称催化中起着重要作用。在这篇综述中，解释了如何利用铵离子的不对称离子对催化作用在有机合成中，特别是在新型催化循环的设计中。这包括使用手性铵基催化剂构建具有挑战性的手性中心。铵衍生的亲电试剂，通常在相转移催化（PTC）的情况下原位形成，也已被用于不对称键形成反应中。此外，铵盐已被用作几种立体控制 C-N 键断裂过程的底物，通过使用新型不对称诱导模式，得到对映体富集的产物。此外，将铵离子对催化与其他催化方法相结合也已成为实现以前不太直接的反应的新平台，从而为新的合成应用开辟了道路。
