Spirocyclic Oxindole and Dihydrobenzofuran Formation via a Dearomative Cyclization–Nucleophilic Trapping Sequence

Dearomative difunctionalization of heteroarenes represents a convenient method toward heteroalicyclic compounds by breaking the aromaticity and forming two chemical bonds in a single step. Herein, a palladium-catalyzed alkenyletherification of indoles is disclosed through dearomative spirocyclization of <i>C</i>3-alkyne-tethered indoles, followed by intermolecular nucleophilic addition of the generated iminium with MeOH, affording a series of spirooxindoles in moderate to good yields after an additional oxidation. In addition, dearomative alkenylacetoxylation of <i>C</i>3-alkyne-tethered benzofurans with AcOH is also achieved toward spirodihydrobenzofurans in moderate to excellent yields. Preliminary exploration of the asymmetric version and synthetic transformation of the product are investigated.