Ortho-Selective Dearomative [2+2] Photocycloadditions of Bicyclic Aza-Arenes

Dearomative photocycloadditions are valuable chemicaltransformations,serving as an efficient platform to create three-dimensional molecularcomplexity. However, the photolability of the original addition productespecially within the context of ortho cycloadditionsoften causes undesired consecutive rearrangements, rendering these ortho cycloadducts elusive. Herein, we report an ortho-selective intermolecular photocycloaddition of bicyclicaza-arenes including (iso)-quinolines, quinazolines, and quinoxalinesby utilizing a strain-release approach. With bicyclo[1.1.0]-butanesas coupling partners, this dearomative [2 pi + 2 sigma] cycloadditionenables the straightforward construction of C-(sp(3))-richbicyclo-[2.1.1]-hexanes directly connected to N-heteroarenes. Photophysicalexperiments and DFT calculations revealed the origin of the [2 pi+ 2 sigma] selectivity and indicate that, in addition to the originallyproposed energy transfer or direct excitation pathways, a chain reactionmechanism is operative depending on the reaction conditions.