Formal Catalytic Cleavage of C(sp2)–C(sp2) Bonds Enabled the Construction of Dihydropyran-Fused Indoles

Deconstructive functionalization reactions involving the selective scission of C═C bonds have been established. This strategy used both sp2-hybridized carbons as functional groups and functionalized the remote unactivated C–H of arenes using a palladium-catalyzed domino reaction. Alkene-tethered carbamoyl chlorides and aryl bromides (triflates) were compatible as starting materials under the same reaction conditions, enabling the convergent and complementary synthesis of dihydropyran-fused indoles. The reaction mechanism was explored using control experiments, NMR studies, and density functional theory (DFT) calculations. These studies suggested that the reaction proceeded via sequential Pd-catalyzed domino Heck/C–H activation to form a spirooxindole intermediate, followed by 4π-electrocyclic ring opening and then a 6π-electrocyclization mechanism.