Ring expansion of unsubstituted aziridinium ylides to trifluoromethylated dehydropiperidines

Abstract

The first rhodium-catalyzed [3 + 3] ring expansion of unsubstituted aziridines was achieved using trifluoroalkenyl N-triftosylhydrazones as vinylcarbene precursors to afford a series of structurally diverse 2-trifluoromethylated dehydropiperidines under mild conditions. DFT calculations supported a scheme involving aziridinium ylide formation followed by a [1,4] sigmatropic rearrangement sequence. Notably, the reaction shows broad scope and functional group tolerance, which enables the translation of routine olefination of unsubstituted aziridinium ylides into a strategy for heterocyclic ring syntheses. Beyond enabling access to valuable dehydropiperidines from easily prepared starting materials, we also demonstrated the synthetic utility of this approach in the late-stage modification of bioactive compounds.