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

Combining an electrophilic iron complex [Fe( pda)(THF)] (3) [ pda=N,N'-bis(pentafluorophenyl)-o-phenylenediamide] with the pre-activation of α-alkyl-substituted α-diazoesters reagents by LiAl(OR ) [OR =(OC(CF ) ] provides unprecedented access to selective iron-catalyzed intramolecular functionalization of strong alkyl C(sp )-H bonds. Reactions occur at 25 °C via α-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.