Rh(II)-Catalyzed Access to [4.3.1]Propellanes via a Formal Dicarbene Cascade Annulation

The first dirhodium(II)-catalyzed synthesis of propellanes is established via a formal dicarbene-mediated cyclopropanation/C–H insertion cascade using readily available 1,6-enynes as carbene precursors. A key finding is that the competitive pathway between C–H insertion and carbene dimerization can be effectively controlled through solvent regulation. This one-pot transformation afforded a challenging chiral [4.3.1.0 1,6 ]-bridged compound containing three rings and vicinal all-carbon quaternary stereocenters.