Rhodium‐Catalyzed Asymmetric Cyclopropanation of Indoles with N‐Triftosylhydrazones

Abstract

AbstractHerein we report a general rhodium‐catalyzed asymmetric intermolecular dearomative cyclopropanation of indoles using trifluoromethyl N‐triftosylhydrazones as carbene precursors. The reaction enables the rapid construction of diverse cyclopropane‐fused indolines bearing a trifluoromethylated quaternary stereocenter with high enantioselectivity (up to 99 % ee). This mild method exhibits broad substrate scope, tolerating various functional groups, and can even be utilized for the late‐stage diversification of complex bioactive molecules. DFT calculations suggest that the formation of a key zwitterionic intermediate is responsible for the chiral induction. Overall, this approach opens up new possibilities for asymmetric cyclopropanation of challenging aromatic heterocyclic compounds.