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.