Catalyst-Free <i>gem</i>-Difluorination/Spirocyclization of Indole-2-carboxamides: Synthesis of C2-Spiroindoline Derivatives

Abstract

A catalyst-free gem -difluorination/spirocyclization reaction has been successfully developed for the synthesis of gem -difluorinated C2-spiroindoline derivatives from indole-2-carboxamides. The resulting gem -difluorinated C2-spiroindolines can be easily converted into 2-spiropseudoindoxyls through hydrolysis. This method offers the benefits of simple operation, convenient access to raw materials, and mild conditions. Dual function of Selectfluor in this reaction is noteworthy as it can serve as both a fluorinating agent and an alkaline accelerator precursor.