Synthesis and Activation of Bench-Stable 3a-Fluoropyrroloindolines as Latent Electrophiles for the Synthesis of C‑2-Thiol-Substituted Tryptophans and C‑3a-Substituted Pyrroloindolines

Indole dearomatization of tryptophan represents a key approach in the synthesis of indole containing alkaloids. Although the reactivity of C-3a-bromo-, 3a-iodo-, and 3a-chloro­pyrroloindolines has been explored, the utility and reactivity of C-3a-fluoro­pyrroloindolines has remained untapped. Here we induce the C–F bond to undergo a S_n1-like reaction. We demonstrate the utility of 3a-fluoropyrroloindoline to access C-2-thiol-substituted tryptophans and C-3a-substituted pyrroloindolines under mild conditions in high yield. A range of N^α-protecting groups and free -COOH are well-tolerated.