Engaging electronic effects for atropselective [5+2]-photocycloaddition of maleimides.

Atropisomeric maleimides were synthesized and subjected to atropselective [5+2]-photocycloaddition under direct irradiation to yield azepinone products with high enantio- (ee >98%) and diastereoselectivity (dr >98%). While the ee was dictated by the axial chirality, the dr was influenced by the substituent on the maleimide ring. Interestingly, by tuning the electronics of the substituent, the dr of the product can be reversed.