Dearomative cycloaddition reactions represent an ideal means of converting flat arenes into three-dimensional architectures of increasing interest in medicinal chemistry. Quinolines, isoquinolines, and quinazolines, despite containing latent diene and alkene subunits, are scarcely applied in cycloaddition reactions because of the inherent low reactivity of aromatic systems and selectivity challenges. Here, we disclose an energy transfer-mediated, highly regio- and diastereoselective intermolecular [4 + 2] dearomative cycloaddition reaction of these bicyclic azaarenes with a plethora of electronically diverse alkenes. This approach bypasses the general reactivity and selectivity issues, thereby providing various bridged polycycles that previously have been inaccessible or required elaborate synthetic efforts. Computational studies with density functional theory elucidate the mechanism and origins of the observed regio- and diastereoselectivities.

Photochemical dearomative cycloaddition has emerged as a useful strategy to rapidly generate molecular complexity. Within this context, stereo- and regiocontrolled intermolecular para-cycloadditions are rare. Herein, a method to achieve photochemical cycloaddition of quinolines and alkenes is shown. Emphasis is placed on generating sterically congested products and reaction of highly substituted alkenes and allenes. In addition, the mechanistic details of the process are studied, which revealed a reversible radical addition and a selectivity-determining radical recombination. The regio- and stereochemical outcome of the reaction is also rationalized.