Chiral Ferrocenes in Asymmetric Catalysis

Chiral ferrocenes have emerged as pivotal building blocks in asymmetric catalysis, offering unique advantages derived from their stable sandwich structure and planar chirality. The introduction of chirality into the ferrocene scaffold transforms it into an effective ligand framework capable of inducing high levels of enantioselectivity across a range of transformations. Their versatility is underpinned by facile modification at the cyclopentadienyl rings, enabling the fine-tuning of electronic and steric properties to suit diverse catalytic systems. Recent advances in direct C–H functionalisation, ligand design and mechanistic understanding have broadened the scope of ferrocene-derived catalysts, enhancing their global impact in pharmaceutical synthesis, agrochemicals and fine-chemical production. Innovations in electrochemical methodologies and non-precious metal catalysis have further underscored the potential of chiral ferrocenes to meet the growing demand for sustainable and highly enantioselective processes.

Research from Nature Portfolio

Recent studies have unveiled new strategies for constructing planar chiral ferrocenes via transition-metal catalysed C–H functionalisation. One approach employs a modified BINOL-derived ligand to accelerate copper(II)-mediated enantioselective C–H alkynylation, enabling the efficient synthesis of alkynylated ferrocenes with high yields and enantioselectivities under mild conditions. This protocol demonstrates compatibility with both aryl and alkyl alkynes, expanding the toolkit for diversifying ferrocene-based catalysts. A separate investigation has introduced an electrochemically driven dehydrogenative C–H phosphorylation of group 8 metallocenes, using electrochemical initiation to generate phosphoryl radicals that engage the ferrocene core with excellent regioselectivity. This method provides a sustainable route to phosphorylated ferrocenes and offers mechanistic insight into radical-mediated C–H activation. Foundational work with thioketone-directed rhodium(I) catalysis remains influential, having established an enantioselective C–H arylation of ferrocenes to deliver planar chiral products in exceptional yields and stereocontrol through the use of phosphonite ligands.

Chiral Ferrocenes in Asymmetric Catalysis publication trend

The graph below shows the total number of articles in chiral ferrocenes in asymmetric catalysis across all publications each year (not limited to Nature Index journals).

Technical terms

Planar chirality: A form of stereoisomerism arising when an achiral molecule becomes chiral due to the arrangement of substituents in a plane, as seen in substituted ferrocenes.

C–H activation: A catalytic process in which a carbon–hydrogen bond is cleaved and functionalised, enabling direct transformation of hydrocarbons into more complex structures.

Enantioselectivity: The preference of a catalyst or reaction to form one enantiomer over its mirror image, usually expressed as enantiomeric excess.

Directing group: A functional moiety installed on a substrate to guide a catalyst to a specific C–H bond, enhancing reactivity and selectivity in C–H functionalisation.

References

1. Cu-mediated enantioselective C–H alkynylation of ferrocenes with chiral BINOL ligands. Nature Communications (2023).
2. Electrochemically driven regioselective C−H phosphorylation of group 8 metallocenes. Nature Communications (2022).
3. Thioketone-directed rhodium(I) catalyzed enantioselective C-H bond arylation of ferrocenes. Nature Communications (2019).
4. Catalytic Undirected Meta‐Selective C–H Borylation of Metallocenes. Advanced Science (2023).
5. Enantioselective Rh(I)-Catalyzed C–H Arylation of Ferroceneformaldehydes. ACS Central Science (2023).