School of Chemistry, University of Bristol , Bristol, BS8 1TS, United Kingdom.
J Am Chem Soc. 2015 Jan 14;137(1):463-8. doi: 10.1021/ja511335v. Epub 2014 Dec 24.
Upon exposure to neutral or cationic Rh(I)-catalyst systems, amino-substituted cyclopropanes undergo carbonylative cycloaddition with tethered alkenes to provide stereochemically complex N-heterocyclic scaffolds. These processes rely upon the generation and trapping of rhodacyclopentanone intermediates, which arise by regioselective, Cbz-directed insertion of Rh and CO into one of the two proximal aminocyclopropane C-C bonds. For cyclizations using cationic Rh(I)-systems, synthetic and mechanistic studies indicate that rhodacyclopentanone formation is reversible and that the alkene insertion step determines product diastereoselectivity. This regime facilitates high levels of stereocontrol with respect to substituents on the alkene tether. The option of generating rhodacyclopentanones dynamically provides a new facet to a growing area of catalysis and may find use as a (stereo)control strategy in other processes.
在中性或阳离子 Rh(I)-催化剂体系的作用下，氨基取代的环丙烷与连接的烯烃发生羰基加成环化反应，提供具有立体化学复杂性的 N-杂环支架。这些过程依赖于 rhodacyclopentanone 中间体的生成和捕获，这是通过 Rh 和 CO 在两个近位氨基环丙烷 C-C 键之一的区域选择性、Cbz 导向插入而产生的。对于使用阳离子 Rh(I)-体系的环化反应，合成和机理研究表明，rhodacyclopentanone 的形成是可逆的，并且烯烃插入步骤决定了产物的非对映选择性。这种体系有利于对烯丙基取代基的高度立体控制。动态生成 rhodacyclopentanones 的选择为不断发展的催化领域提供了一个新的方面，并可能在其他过程中作为（立体）控制策略得到应用。
