Synthesis and Reactions of 3,3-Difluoro-2-exo-methylidene Indolines.

A dearomative electrophilic fluorination of 2-methylindoles is reported, delivering 3,3-difluoroindolines bearing an exomethylidene. The model substrate was synthesized on up to a 20 mmol scale and was purified by a practical recrystallization as a crystalline bench-stable, yet reactive solid. The olefin is amphoteric and can react both as a nucleophile and as an electrophile. A wide range of metal-free, palladium, rhodium, and copper reactions was explored, forming new C-H, C-B, C-C (alkyl and aryl), C-N, C-O, C-P, and C-S bonds.