π-Electron Fluctuation-Induced P⁺ /C^- Ambiphilic Interaction for Intramolecular C_Ar -H Bond Activation

Herein, we describe how computational mechanistic understanding has led directly to the discovery of new 2H-phosphindole for C-C_Ar bond activation and dearomatization reaction. We uncover an unexpected intramolecular C-H bond activation with a 2H-phosphindole derivative. This new intriguing experimental observation and further theoretical studies led to an extension of the reaction mechanism with 2H-phosphindole. Through DFT calculations, we confirm that within a five-membered ring, the polarizable PC₃ unit orchestrates the formation of an electrophilic phosphorus atom (P⁺ ) and a nucleophilic carbon atom (C^- ). This kinetically accessible ambiphilic phosphorus/carbon couple is spatially separated by geometric constraints, and their reactivity is modulated through structural resonance.