Asymmetric C–H Bond Functionalization of Ferrocenes: New Opportunities and Challenges

Planar chiral ferrocenes have been widely used as privileged scaffolds for the synthesis of effective ligands and catalysts. Transition-metal-catalyzed direct C–H bond functionalization provides a straightforward, convenient, and efficient method to synthesize planar chiral ferrocenes. These methods show advantages over the traditional approaches, such as diastereoselective directed ortho-metalation (DoM), enantioselective DoM, and chiral resolution. The development of appropriate catalytic systems allows enantioselective C–C bond formation starting from readily available ferrocenes. The discovery of catalysts composing of cheap metal further enhances the practicality of these methods. The diverse planar chiral ferrocene products obtained from asymmetric C–H bond functionalization offer a useful platform for the design and synthesis of efficient ligands and catalysts in asymmetric catalysis. Ferrocene is of great significance in the fields of organic synthesis, materials science, and biomedical research. Of particular importance is the fact that ferrocenes with planar chirality have proven to be privileged ligands or catalysts for asymmetric catalysis. Therefore, developing highly efficient methods to introduce planar chirality on the backbone of ferrocene is desirable. This short review highlights recent advances towards enantioselective C–H bond functionalization of ferrocenes. Enantioselective synthesis of planar chiral ferrocenes via Pd-, Ir-, Rh-, Au-, Pt-, and Ni-catalyzed C–H bond functionalization is described. The achievements in asymmetric C–H bond functionalization provide a rich platform for the design and synthesis of planar chiral ferrocenes. Ferrocene is of great significance in the fields of organic synthesis, materials science, and biomedical research. Of particular importance is the fact that ferrocenes with planar chirality have proven to be privileged ligands or catalysts for asymmetric catalysis. Therefore, developing highly efficient methods to introduce planar chirality on the backbone of ferrocene is desirable. This short review highlights recent advances towards enantioselective C–H bond functionalization of ferrocenes. Enantioselective synthesis of planar chiral ferrocenes via Pd-, Ir-, Rh-, Au-, Pt-, and Ni-catalyzed C–H bond functionalization is described. The achievements in asymmetric C–H bond functionalization provide a rich platform for the design and synthesis of planar chiral ferrocenes. a process for the separation of racemic compounds into their enantiomers. a metal/base-promoted C-H bond cleavage occurring by a simultaneous deprotonation and metalation process. the metal undergoes addition of an ortho C–H bond of the aromatic group of a ligand. the deprotonation of site ortho to heteroatom-containing directing group by a strong base, normally an alkyllithium reagent, leading to an ortho-lithiated species. this selectivity results in the formation of an excess of one enantiomer over the other from an achiral or racemic substrate. describing the relationship between two C–H bonds, which, if replaced, would generate compounds that are enantiomers. the nucleophilic arene interacts with an electrophilic metal intermediate via a Wheland-like intermediate.