Visible-Light-Induced Asymmetric Dearomative [2 + 2] Cycloaddition of Aza-arenes with Bicyclo[1.1.0]butanes

Dearomative photocycloaddition reactions of (hetero)arenes offer a powerful route to three-dimensional molecular scaffolds with high value in medicinal chemistry. Summarized here are recent progress on strain-release accelerated dearomative photocycloaddition with bicyclo[1.1.0]butanes and highly regio- and enantioselective [2 + 2] cycloadditions of quinolines and indole derivatives. Key to the success of the reaction is the strategic design of chiral N,N′-dioxide/metal Lewis acid catalysts with tailored steric bulk that can modulate the chiral pocket to adapt to the varied electronic and steric characteristics of different substrate substituents. The catalyst’s role and the origin of stereoselectivities were elucidated based on experimental studies and theoretical calculation.