Electrophilic Iron Catalyst Paired with a Lithium Cation Enables Selective Functionalization of Non-Activated Aliphatic C-H Bonds via Metallocarbene Intermediates

摘要

Combining an electrophilic iron complex [Fe((F)pda)(THF)](2) (3) [(F)pda=N,N '-bis(pentafluorophenyl)-o-phenylenediamide] with the pre-activation of alpha-alkyl-substituted alpha-diazoesters reagents by LiAl(ORF)(4) [ORF=(OC(CF3)(3)] provides unprecedented access to selective iron-catalyzed intramolecular functionalization of strong alkyl C(sp(3))-H bonds. Reactions occur at 25 degrees C via alpha-alkyl-metallocarbene intermediates, and with activity/selectivity levels similar to those of rhodium carboxylate catalysts. Mechanistic investigations reveal a crucial role of the lithium cation in the rate-determining formation of the electrophilic iron-carbene intermediate, which then proceeds by concerted insertion into the C-H bond.