Enantioselective propargylic [1,3]-rearrangements: copper-catalyzed -to- migrations toward C-N bond formation.

We have identified an enantioselective copper-catalyzed -to- formal [1,3]-rearrangement to form -propargylic-2-pyridones. This enantioconvergent -to- propargylic rearrangement occurs rapidly at ambient temperature and high enantioselectivity is observed for a range of 3-alkyl-substituted substrates. Stereochemical features include a mild kinetic enantioenrichment of the substrate and a non-linear relationship between product and ligand enantiopurity. Based on kinetic analyses and cross-over experiments, we put forward a mechanistic proposal involving Cu-acetylides as well as bimetallic intermediates in which coordination to the pyridyl nitrogen is likely a crucial binding interaction.