Gold-Catalyzed Intermolecular Formal Insertion of Aryldiazo Esters into Cp-H Bonds of Cp2M (M = Fe, Ru)

Abstract

The reaction of ferrocene (and ruthenocene) with aryldiazo acetates in the presence of gold catalysts provided new functionalized metallocenes resulting from a C-H bond functionalization process. This process is believed to proceed through initial decomposition of the diazo component with formation of an electrophilic gold carbene intermediate, which would be subsequently involved in an electrophilic aromatic substitution. The gold-catalyzed functionalization of ruthenocene exhibited a broad scope and a notable functional-group tolerance. Interestingly, the functionalized ferrocene derivatives were found to react with molecular oxygen to yield -aryl--ferrocenyl--hydroxyacetates. Adsorption on silica gel was found to be essential for this dioxygen activation/C(sp3)-H bond functionalization sequence. The methodologies reported herein provide a simple and efficient approach to functionalized metallocene derivatives difficult-to-access through conventional organic functional group transformations.