Palladium-Catalyzed C-H Functionalization of Ferrocene-carboxylic Acid by using 8-Aminoquinoline as a Removable Directing Group

A mild and efficient palladium-catalyzed synthetic method for the C-H functionalization of N-(quinolin-8-yl)ferrocenecarboxamide has been developed. Various aryl iodides containing I, NO2, CN, COMe, CO2Et, and NH functionalities and also alkyl iodides underwent the Pd-catalyzed intermolecular carbon-carbon bond forming reaction with ferrocenecarboxamide successfully which led to a diverse array of bis(aryl/alkyl)ferrocenecarboxamides in 34-92% yields. Cross-coupling of the ferrocenyl C-H bond with aryl iodides can also be achieved utilizing an economical Ni catalyst. Additionally, selective monoalkylation of ferrocenecarboxamide was studied using sodium bicarbonate as base and dibenzyl-phosphoric acid as additive under Pd-catalyzed reaction conditions. Subsequently, removal of the directing group, 8-aminoquinoline, from bis(aryl)ferrocenecarboxamides led to bis(aryl)ferrocenes bearing versatile methyl ester and carboxaldehyde functional groups.