Intermolecular [2 + 2] Cycloaddition of 1,4-Dihydropyridines with Olefins via Energy Transfer

A highly regio- and diastereoselective visible-light-promoted [2 + 2] cycloaddition between readily available 1,4-dihydropyridines and olefins has been developed. This strategy is operationally simple and atom-economical and enables the construction of strained polysubstituted 2-azabicyclo[4.2.0]­octanes with three all-carbon quaternary centers with good functional group tolerance. These products can be easily converted to various structurally unique derivatives. The primary mechanistic studies demonstrated that the reaction proceeds through an energy transfer pathway.