RESUMO
A novel class of alkyne-tethered amides facilitates an unprecedented photoinduced palladium-catalyzed radical relay formal [5 + 2] reaction. This innovative strategy allows for the rapid construction of diverse fused benzoazepine structures, yielding structurally novel and compelling compounds. With a broad substrate scope and excellent functional group tolerance, the methodology synthesizes biologically active compounds. Notably, the resulting tricyclic benzo[b]azepines offer diversification opportunities through simple transformations. DFT calculations elucidate a seven-membered ring closure mechanism involving the alkenyl radical and Pd(I) rebound alongside a concerted metalation-deprotonation (CMD) process.
RESUMO
Here, a palladium-catalyzed photoinduced N-to-alkyl radical relay Heck reaction of o-alkylbenzamides at benzylic sites with vinyl arenes is described. The reaction employs neither exogeneous photosensitizers nor external oxidants. It is proposed to proceed via a N-to-alkyl hybrid palladium-radical mechanism which occurs under mild conditions that are compatible with a wide range of functional groups. The products are easily transformed to azepinone derivatives, which are prevalent in pharmaceuticals and natural products.
RESUMO
A palladium-catalyzed aryl-to-alkyl radical relay Heck reaction of amides at α-C(sp3)-H sites with vinyl arenes is described. This process displays a broad substrate scope with respect to both amide and alkene components and provides access to a diverse class of more complex molecules. The reaction is proposed to proceed via a hybrid palladium-radical mechanism. The core of the strategy is that the fast oxidative addition of aryl iodide and fast 1,5-HAT overcome the slow oxidative addition of alkyl halides, and the photoexcitation effect suppresses the undesired ß-H elimination. It is anticipated that this approach would inspire the discovery of new palladium-catalyzed alkyl-Heck methods.
