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.

Iodoferrocene as a partner inN-arylation of amides

A general copper-promoted amidation of iodoferrocene is described toward original scaffolds that can be further functionalized by cross-coupling reactions.

Regorafenib analogues and their ferrocenic counterparts: synthesis and biological evaluation

New ferrocene analogues of regorafenib have been prepared and their biological activity was evaluated in kinase and cellular assays.

Platinum(IV)-Ferrocene Conjugates and Their Cyclodextrin Host-Guest Complexes

Reported here are new platinum(IV) (Pt(IV)) complexes bearing ferrocene (Fc) moieties. These systems differ from one another only by the nature of the functional group (ester vs amide) connecting the linker to the Fc subunits. This minor structural variation (one atom difference) leads to major differences in solubility, stability, and antiproliferative activity against lung (A549) cancer cells. The host-guest chemistry of these complexes was investigated in an aqueous medium in the presence of β-cyclodextrins (β-CD), either free or in the form of a covalently linked Fc-Pt-β-CD hybrid. An inclusion complex between Fc and β-CD is formed in aqueous media, presumably as a result of hydrophobic interactions involving the Fc and the inner β-CD cavity. Consequently, it proved possible to use a β-CD-based strategy to purify the Pt-Fc conjugates in this study under aqueous conditions (by means of C18 silica gel columns). The use of a β-CD adjuvant also allowed dimethyl sulfoxide (DMSO) to be avoided as an organic cosolvent in cell studies. The amide version reported here (2) proved to be more soluble, more stable, and more active than the ester analogue (11) in A549 cells. The use of a β-CD functionalized with a fluorescent probe allowed intracellular Pt-Fc localization to be visualized by confocal fluorescence microscopy.

Ferrocenecarboxylic anhydride: identification of a new polymorph

A new monoclinic polymorph of ferrocenecarboxylic anhydride, [Fe₂(C₅H₅)₂(C₁₂H₈O₃)], was obtained. Three molecules are present in the asymmetric unit, two of them being nearly identical (r.m.s. deviation = 0.11 Å), with the Fe atoms on the same side of the anhydride functional group. In the third molecule, the two Fe atoms are located at opposite sides of the functional group (ferrocene-ferrocene pseudo-torsion angle = 146.2°), a very unsual feature in metallocene anhydrides. A network of weak intermolecular hydrogen bonds was also disclosed.