Native Carboxylate Assisted Palladium/Norbornene Mediated Distal C-H functionalization of Ferrocene

The traditional directing group approach for transition metal catalyzed C-H functionalization requires an exogenous auxiliary with strong coordinating ability for the selective C-H activation and therefore involves extra steps for its installation and removal after the reaction. Herein, we disclose a ligand enabled auxiliary-free, native carboxylate assisted Pd/norbornene(NBE) mediated highly regioselective C(3)-arylation of commercially available ferrocene carboxylic acids. This unique DG-free approach utilizes the Catellani-type reaction for the distal C-H activation in ferrocene where the weak chelation-assisted palladacycle formed by proximal C-H activation could relay palladium to the distal C(3)-position mediated by NBE resulting into C-C bond formation with aryl iodides. Both the norbornene derivative and the monoprotected 3-amino-2-hydroxypyridine ligand used are crucial for the successful formation of FNP intermediate, thus resulting into C(3)-arylated ferrocene carboxylic acid formation.