Stereoselective synthesis of planar chiral 2,2′-diarylsubstituted ferrocene derivatives as precursors for new 2-phospha[3]ferrocenophanes

Recent Advances in the Catalytic Synthesis of the Cyclopentene Core

Five-membered carbocycles are ubiquitously found in natural products, pharmaceuticals, and other classes of organic compounds. Within this category, cyclopentenes deserve special attention due to their prevalence as targets and as well as key intermediates for synthesizing more complex molecules. Herein, we offer an overview summarizing some significant recent advances in the catalytic assembly of this structural motif. A great variety of synthetic methodologies and strategies are covered, including transition metal-catalyzed or organocatalyzed processes. Both inter- and intramolecular transformations are documented. On this ground, our expertise in the application of C-H functionalization reactions oriented towards the formation of this ring and its subsequent selective functionalization is embedded.

From ferrocene to decasubstituted enantiopure ferrocene-1,1'-disulfoxide derivatives

The functionalization of (R,R)-S,S'-di-tert-butylferrocene-1,1'-disulfoxide by deprotolithiation-electrophilic trapping sequences was studied towards polysubstituted, enantiopure derivatives for which the properties were determined. While the 2,2'-disubstituted ferrocene derivatives were obtained as expected, subsequent functionalization of the 2,2'-di(phenylthio) and 2,2'-bis(trimethylsilyl) derivatives occurred primarily at the 4- or 4,4'-positions. This unusual regioselectivity was discussed in detail in light of pK_a values and structural data. The less sterically hindered 2,2'-difluorinated derivative yielded the expected 1,1',2,2',3,3'-hexasubstituted ferrocenes by the deprotometallation-trapping sequence. Further functionalization proved possible, leading to early examples of 1,1',2,2',3,3',4,4'-octa, nona and even decasubstituted ferrocenes. Some of the newly prepared ferrocene-1,1'-disulfoxides were tested as ligands for enantioselective catalysis and their electrochemical properties were investigated.

A New Class of C2 -Symmetric Chiral Cyclopentadienyl Ligand Derived from Ferrocene Scaffold: Design, Synthesis and Application

A new class of C₂ -symmetric, chiral cyclopentadienyl ligand based on planar chiral ferrocene backbone was developed. A series of its corresponding rhodium(I), iridium(I), and ruthenium(II) complexes were prepared as well. In addition, the rhodium(I) complexes were evaluated in the asymmetric catalytic intramolecular amidoarylation of olefin-tethered benzamides via C-H activation.

Phosphine Organocatalysis

The hallmark of nucleophilic phosphine catalysis is the initial nucleophilic addition of a phosphine to an electrophilic starting material, producing a reactive zwitterionic intermediate, generally under mild conditions. In this Review, we classify nucleophilic phosphine catalysis reactions in terms of their electrophilic components. In the majority of cases, these electrophiles possess carbon-carbon multiple bonds: alkenes (section 2), allenes (section 3), alkynes (section 4), and Morita-Baylis-Hillman (MBH) alcohol derivatives (MBHADs; section 5). Within each of these sections, the reactions are compiled based on the nature of the second starting material-nucleophiles, dinucleophiles, electrophiles, and electrophile-nucleophiles. Nucleophilic phosphine catalysis reactions that occur via the initial addition to starting materials that do not possess carbon-carbon multiple bonds are collated in section 6. Although not catalytic in the phosphine, the formation of ylides through the nucleophilic addition of phosphines to carbon-carbon multiple bond-containing compounds is intimately related to the catalysis and is discussed in section 7. Finally, section 8 compiles miscellaneous topics, including annulations of the Hüisgen zwitterion, phosphine-mediated reductions, iminophosphorane organocatalysis, and catalytic variants of classical phosphine oxide-generating reactions.

One-stage synthesis of FcP(O)(OC2H5)2from ferrocene and α-hydroxyethylphosphonate

A new approach is proposed for ferrocene phosphorylation using α-hydroxylalkylphosphonate as a “masked” phosphorylating agent, by electrochemical reduction of a ferrocene and (Me)₂C(OH)P(O)(OC₂H₅)₂mixture at −50 °C.

Chiral bifunctional ferrocenylphosphine catalyzed highly enantioselective [3 + 2] cycloaddition reaction

The asymmetric [3 + 2] annulation catalyzed by air-stable (R,S_Fc)-N-acyl amino ferrocenylphosphines LB5 affords the bicyclic imides with 84–99% ee and 67–99% yield.