Frustrated Lewis Pair catalyzed cycloisomerization initiated by hydride abstraction

环异构化、环加成和电环化是合成具有四元立体中心的复杂分子框架的有力工具。特别是，人们认为，微量离子是诱发这类反应的活性中间体。虽然无环叔胺离子很容易获得，例如通过缩合，但合成相应的环衍生物需要大量的合成努力。然而，在受挫的Lewis对催化反应中已经观察到胺离子的形成，这为这些活性中间体的有效获取开辟了新的领域。本研究项目利用了迄今为止尚未开发的催化C-C键形成反应的合成潜力，合成了含季立体中心的喹啉衍生物。这种重要的分子类是由氢化物萃取引发的催化形成的铝离子的电环化得到的。灵活的取代模式为有效地获得具有四元立体中心的多环生物碱衍生物开辟了道路。此外，通过这种新的催化方法不仅可以得到四氢喹啉，而且可以得到二氢喹啉。通过对催化剂的选择，反应可以指向氧化中性环异构化或迄今为止前所未有的脱氢环异构化，从相同的底物中获得两种重要的药理学产物。

Cycloisomerizations, cycloadditions and electrocyclizations are powerful tools for the synthesis of complex molecular frameworks bearing quaternary stereogenic centers. In particular, iminium ions are recognized as reactive intermediates to induce such reactions. While acyclic tertiary iminium ions are readily accessible e.g. though condensation, substantial synthetic effort is required for the synthesis of the corresponding cyclic derivatives. However, the formation of iminium ions has been observed in frustrated Lewis pair-catalyzed reactions, which breaks new ground for the efficient access to these reactive intermediates.This research project takes advantage of this so far unexploited synthetic potential for the catalytic C–C bond forming reaction in the synthesis of quinoline derivatives bearing quaternary stereocenters. This important molecule class is obtained by hydride abstraction-initiated electrocyclization of catalytically formed iminium ions. The flexible substitution pattern opens up for the efficient access to polycyclic alkaloid derivatives with quaternary stereocenters. Furthermore, not only tetrahydroquinolines but also dihydroquinolines are accessible by this new catalytic approach. Through the choice of the catalyst the reaction can be directed to the redoxneutral cycloisomerization or to the so far unprecedented dehydrogenative cycloisomerization accessing two pharmacologically important product classes from the same substrate.