Rhodium-catalyzed intramolecular conjugate addition of vinylstannanes to dihydro-4-pyridones: a simple method for stereoselective construction of 1-azabicyclic alkaloids

A straightforward route for the stereoselective synthesis of unsaturated quinolizidines and related higher homologs has been developed. Our results revealed that the rhodium complex [RhCl(cod)]2 is an effective catalyst for the intramolecular conjugate addition of vinylstannanes to the dihydropyridones leading to the corresponding 1-azabicyclo[m.n.0]alkenes in a moderate to good yield and an excellent diastereoselectivity under neutral conditions at room temperature. This methodology has been successfully applied to the stereoselective synthesis of the racemic lasubine I.