Divergent Synthesis of Indolenine and Indoline Ring Systems by Palladium‐Catalyzed Asymmetric Dearomatization of Indoles**

摘要

Abstract Dearomatized indole derivatives bearing a C3‐ or C2‐stereocenter exist ubiquitously in natural products and biologically active molecules. Despite remarkable advances in their synthesis, stereoselective and regio‐divergent methods are still in a high demand. Herein, a Pd‐catalyzed intermolecular asymmetric spiroannulation of 2,3‐disubstituted indoles with internal alkynes has been developed for the efficient construction of indoline structures with a C2‐quaternary stereocenter. Stereospecific aza‐semipinacol rearrangement of these indoline derivatives under acidic conditions afforded indolenine products bearing a C3‐quaternary stereocenter, where the migrating group could be controlled by the reaction sequence. The asymmetric spiroannulation together with the subsequent aza‐semipinacol rearrangement enabled a divergent access to dearomatized indole derivatives with either a C3‐ or a C2‐quaternary stereocenter.