The preparation of ferrocene-containing phosphinamine ligands possessing central and planar chirality and their application in palladium-catalysed allylic substitution

Ferrocene derivatives with planar chirality and their enantioseparation by liquid-phase techniques

In the last decade, planar chiral ferrocenes have attracted a growing interest in several fields, particularly in asymmetric catalysis, medicinal chemistry, chiroptical spectroscopy and electrochemistry. In this frame, the access to pure or enriched enantiomers of planar chiral ferrocenes has become essential, relying on the availability of efficient asymmetric synthesis procedures and enantioseparation methods. Despite this, in enantioseparation science, these metallocenes were not comprehensively explored, and very few systematic analytical studies were reported in this field so far. On the other hand, enantioselective high-performance liquid chromatography has been frequently used by organic and organometallic chemists in order to measure the enantiomeric purity of planar chiral ferrocenes prepared by asymmetric synthesis. On these bases, this review aims to provide the reader with a comprehensive overview on the enantioseparation of planar chiral ferrocenes by discussing liquid-phase enantioseparation methods developed over time, integrating this main topic with the most relevant aspects of ferrocene chemistry. Thus, the main structural features of ferrocenes and the methods to model this class of metallocenes will be briefly summarized. In addition, planar chiral ferrocenes of applicative interest as well as the limits of asymmetric synthesis for the preparation of some classes of planar chiral ferrocenes will also be discussed with the aim to orient analytical scientists towards 'hot topics' and issues which are still open for accessing enantiomers of ferrocenes featured by planar chirality.

The Synthesis of Novel P,N-Ferrocenylpyrrolidine-Containing Ligands and Their Application in Pd-Catalyzed Allylic Alkylation – A Synthetic and Mechanistic Investigation

The synthesis of a series of planar chiral P,N-ferrocenylpyrrolidine-containing ligands, with varying substituents at the phosphorus donor atom, is described. The phosphorus donor atom was introduced via a diastereoselective ortho-directed metalation of N-methylpyrrolidinyl ferrocene followed by a quench with various chlorophosphines. These P,N systems are very active in Pd-catalyzed allylic alkylation of 1,3-diphenylpropenyl acetate with dimethylmalonate (conversions of up to 100%) and demonstrated good levels of enantioselectivity (up to 85% ees). Good selectivity for the (R)-enantiomer was observed and mechanistic studies, involving X-ray crystallography and NMR spectroscopic experiments, were employed to help rationalize the observed stereochemical outcome of the reaction.

Advanced Application of Planar Chiral Heterocyclic Ferrocenes

This manuscript is reviewing the superior catalytic activity and selectivity of ferrocene ligands in a wide range of reactions: reduction of ketones, hydrogenation of olefins, hydroboration, cycloaddition, enantioselective synthesis of biaryls, Tsuji–Trost allylation. Moreover, the correlation between a ligand structure and its catalytic activity is discussed in this review.

Design and Synthesis of Pyrrolidinyl Ferrocene-Containing Ligands and Their Application in Highly Enantioselective Rhodium-Catalyzed Olefin Hydrogenation

Herein, we report the design and synthesis of a series of chiral pyrrolidine-substituted ferrocene-derived ligands. The proficiency of this novel structural motif was demonstrated in the Rh-catalyzed asymmetric hydrogenation of dehydroamino acid esters and α-aryl enamides. The products were obtained with full conversions and excellent levels of enantioselectivities of up to >99.9% ee and 97.7% ee, respectively, using a BINOL-substituted phosphine-phosphoaramidite ligand which possesses planar, central, and axial chirality elements.