Carbene cascades for the formation of bridged polycyclic rings

A general strategy to synthesize bridged polycyclic molecules is presented. The synthesis is accomplished via a cascade reaction initiated by rhodium carbene formation. Subsequent intramolecular reaction with an alkyne is then followed by a transannular C-H bond insertion. A rationale for prediction of the major structural isomer that is formed is described and applied to a wide variety of substrates. This rationale is based on conformational and stereoelectronic considerations for the ring system in the substrate.