Asymmetric allylic substitution-isomerization for accessing axially chiral vinylindoles by intramolecular π … π stacking interactions
Ying-xiang Wu, Qi Liu, Qiang Zhang, Zhiwen Ye, Ying He
Abstract
Acyclic axially chiral styrene analogs have attracted substantial research interest in recent years. However, the catalytic synthesis of this kind of molecule is mostly limited to the construction of chiral axes between an alkene and a six-membered ortho-substituted aromatic ring. An efficient strategy for the synthesis of chiral axes bearing an alkene and a five-membered ring is yet to be explored. Herein, we report an asymmetric allylic substitution-isomerization (AASI) for the synthesis of axially chiral vinylindoles bearing Nindole-Cvinyl axes in excellent yields and enantioselectivities. These compounds exhibit configurational stability enabled by intramolecular π … π stacking interactions, which differentiate them from axially chiral alkenes that rely on bulky substitution, hindering rotation. Preliminary mechanistic studies indicate that both intra- and intermolecular pathways are involved in the stereospecific isomerization process.