Photochemical intermolecular dearomative cycloaddition of bicyclic azaarenes with alkenes

Heteroaromatics lured into cycloadditions The Diels-Alder reaction is widely used to produce six-membered carbon rings from alkenes and dienes. Heteroaromatics such as quinolines resemble dienes in principle, but in practice their pairs of double bonds are inert toward cycloadditions because of aromatic stabilization. Ma et al. report that by using an iridium photosensitizer, they could excite quinolines and related azaarenes to triplet states, thereby disrupting the aromaticity and enabling intermolecular, Diels-Alder–like reactivity toward alkenes (see the Perspective by Schmidt). The reactions proceeded exclusively at the flanking carbons outside the nitrogen-containing ring. Science , this issue p. 1338 ; see also p. 1313