Defluorinative Annulation Triggered by Lewis Base-Promoted O-Alkenylation/[3,3]-Sigmatropic Rearrangement of Fluoro-N-arylhydroxylamines: Synthesis of Fused-Indoline Derivatives.

A Lewis base-promoted defluorinative annulation protocol for the preparation of indoline-C2,C3-fused N-heterocyclic scaffolds was described, in which available fluorinated N-arylhydroxylamines, activated alkynes, and ambident N-nucleophiles enabled a modular assembly of diverse indoline-C2,C3-fused N-heterocyclic scaffolds via an interrupted [3,3]-sigmatropic rearrangement of O-alkenyl-N-arylhydroxylamines under mild conditions. This protocol provides a mechanistically distinct and complementary alternative to the established methods for constructing C2,C3-fused indoline architectures.