Generation of Bis(ferrocenyl)silylenes from Siliranes

Divalent silicon species, the so-called silylenes, represent attractive organosilicon building blocks. Isolable stable silylenes remain scarce, and in most hitherto reported examples, the silicon center is stabilized by electron-donating substituents (e.g., heteroatoms such as nitrogen), which results in electronic perturbation. In order to avoid such electronic perturbation, we have been interested in the chemistry of reactive silylenes with carbon-based substituents such as ferrocenyl groups. Due to the presence of a divalent silicon center and the redox-active transition metal iron, ferrocenylsilylenes can be expected to exhibit interesting redox behavior. Herein, we report the design and synthesis of a bis(ferrocenyl)silirane as a precursor for a bis(ferrocenyl)silylene, which could potentially be used as a building block for redox-active organosilicon compounds. It was found that the isolated bis(ferrocenyl)siliranes could be a bottleable precursor for the bis(ferrocenyl)silylene under mild conditions.     

Synthesis,characterization and evaluation of heterobimetallic Fe(II)/Rh(I) and Fe(II)/Ru(II) complexes as catalyst precursors for hydroformylation of 1-octene

Abstract

Two new ferrocenyl iminopyridyl ligands, L1 and L2, have been synthesized and characterized using spectroscopic and analytical techniques. Both ligands were used to prepare new Rh(I) and Ru(II) ferrocenyl complexes 1–4. The structures of the complexes were confirmed using ¹H and ¹³C nuclear magnetic resonance spectroscopy, high resolution electrospray ionization mass spectrometry, and infrared spectroscopy. The complexes were tested as catalysts in the hydroformylation of 1-octene. Rh ferrocenyl complexes 1 and 4 produced aldehydes under mild conditions while the Ru-ferrocenyl complexes 2 and 3 required higher temperature and pressure for effective hydroformylation to occur. The catalysts display excellent aldehyde chemoselectivity with varying regeoselectivity depending on temperature and pressure conditions employed. At high temperatures, the Rh ferrocenyl precatalysts favor formation of branched aldehydes due to increased isomerization at high temperatures. The Ru ferrocenyl precatalysts displayed less hydroformylation activity; however, the complexes show good chemoselectivity for aldehydes with no hydrogenation products formed.     

A neo-pentyl-ferrocene motif for the synthesis of electroactive polyesters

Several new neo-pentylenediol based ferrocenyl molecules have been prepared using Friedel-Crafts acylation and Clemmensen reduction techniques. The acyl or methyl linker by which the ferrocenyl group is attached tunes the redox properties of the small molecule. The X-ray crystal structure of the acylferrocene with protecting ester groups, its derivative dialcohol, and the methylferrocene dialcohol compounds are reported. Melt polymerisation conditions result in an elimination from the acyl monomer, but a mild carbodiimide coupling protocol successfully generates a number of neo-pentylenediol/aromatic dicarboxylate polyesters with pendant ferrocenyl groups.     

Efficient and Environmentally Friendly Approach to the Synthesis of Ferrocenyl‐Substituted 1,5‐Diketone Compounds Under Solvent‐Free Conditions

Abstract

This article describes a fast, efficient, economical, and environmentally friendly method for the preparation of a series of ferrocenyl‐substituted 1,5‐diketone compounds via Michael addition of ferrocenyl‐substituted chalcones with deoxybenzoin or dibenzyl ketone under solvent‐free conditions, and affords the corresponding Michael adducts with excellent yields of 77–93%.     

Conducting ferrocene monolayers on nonconducting surfaces

The redox activity of a ferrocenyl monolayer grafted on an n-type Si111 substrate was investigated by scanning electrochemical microscopy (SECM) in conditions where the substrate plays the role of an insulator. This approach permits the differentiation between the different possible electron-transfer and mass-transport pathways occurring at the interface. As an exciting result, the thin ferrocenyl monolayer behaves like a purely conducting material, highlighting very fast electron communication between immobilized ferrocenyl headgroups in a 2D-like charge-transport mechanism.     

Etherification of Ferrocenyl Alcohol by Highly‐efficient Ytterbium Triflate

Nucleophilic substitution of ferrocenyl alcohols with various aliphatic alcohols in the presence of a catalytic amount of ytterbium triflate [Yb(OTf)₃] was studied. It was found the unsymmetrical ferrocenyl ethers could be easily obtained in excellent yields when the reactions were performed in primary and secondary alcohols. However, in other organic non‐alcoholic solvents such as acetonitrile, the formation of symmetrical ferrocenyl ethers rather than unsymmetrical ones was observed.     

全共轭型二茂铁基聚合物

由于二茂铁独特的夹心结构使含二茂铁基聚合物具有独特的电、磁、催化以及氧化还原性能。全共轭型二茂铁基聚合物由于其特殊的π-π电子结构,使其在电学、光学等方面的表现出优越的性质。本文从3个方面（主链型、侧链型和超支化型）介绍了近年来含有二茂铁基团全共轭聚合物的合成及其性能方面的研究进展,讨论了聚合物的结构对溶解性、氧化还原性等方面的影响,并探讨了这一领域存在的问题及可能的发展方向。     

Ferrocenyl‐Modified DNA: Synthesis,Characterization and Integration with Semiconductor Electrodes

The ferrocenyl‐nucleoside, 5‐ethynylferrocenyl‐2′‐deoxycytidine ( 1 ) has been prepared by Pd‐catalyzed cross‐coupling between ethynylferrocene and 5‐iodo‐2′‐deoxycytidine and incorporated into oligonucleotides by using automated solid‐phase synthesis at both silica supports (CPG) and modified single‐crystal silicon electrodes. Analysis of DNA oligonucleotides prepared and cleaved from conventional solid supports confirms that the ferrocenyl‐nucleoside remains intact during synthesis and deprotection and that the resulting strands may be oxidised and reduced in a chemically reversible manner. Melting curve data show that the ferrocenyl‐modified oligonucleotides form duplex structures with native complementary strands. The redox potential of fully solvated ferrocenyl 12‐mers, 350 mV versus SCE, was shifted by +40 mV to a more positive potential upon treatment with the complement contrary to the anticipated negative shift based on a simple electrostatic basis. Automated solid‐phase methods were also used to synthesise 12‐mer ferrocenyl‐containing oligonucleotides directly at chemically modified silicon <111> electrodes. Hybridisation to the surface‐bound ferrocenyl‐DNA caused a shift in the reduction potential of +34 mV to more positive values, indicating that, even when a ferrocenyl nucleoside is contained in a film, the increased density of anions from the phosphate backbone of the complement is still dominated by other factors, for example, the hydrophobic environment of the ferrocene moiety in the duplex or changes in the ferrocene–phosphate distances. The reduction potential is shifted >100 mV after hybridisation when the aqueous electrolyte is replaced by THF/LiClO₄, a solvent of much lower dielectric constant; this is consistent with an explanation based on conformation‐induced changes in ferrocene–phosphate distances.     

Die konformationsenergie des ferroc̄enylrestes

From equilibration experiments with ferrocenyl cyclohexanes substituted at position 4, an average conformational free enthalpy of 2.9±0.1 kcal/mole was established for the ferrocenyl group. The spatial requirement of ferrocenyl at the equilibrium equatorial ? axial is approximately equivalent to that of the phenyl residue (3.0±0.1 kcal/mole).     

Preparation,characterization and biological activities of novel ferrocenyl‐substituted azaheterocycle compounds

α‐Haloacetylferrocene and α‐triazolylacetylferrocene have been prepared from acetylferrocene and they have proved to be useful building blocks for the synthesis of ferrocenyl propenone. Two new types of ferrocenyl vinyl triazole compound, (Z,E)‐ferrocenyl‐[1‐(1,2,4‐triazol‐1‐yl)‐2‐phenyl]‐vinyl‐ones, have been synthesized and their structures characterized by crystal X‐ray diffraction analysis. It has been shown for the first time that ferrocene, as an organometallic compound, has been introduced into bioactive triazole compounds in search of potent bioactive substances. Their biological activities are also discussed. Copyright © 2003 John Wiley & Sons, Ltd.     

Novel ferrocenyl phosphonate derivatives. Inhibition of serine hydrolases by ferrocene azaphosphonates

Owing to their unique properties, ferrocene compounds are gaining increasing interest for biological applications, particularly as enzyme inhibitors. Phosphonate derivatives including a ferrocenyl moiety were synthesized by reaction of dimethyl‐ and diphenylphosphite with ferrocenyl methyl maleimide. The ferrocenyl diphenyl phosphonate complex was characterized by X‐ray diffraction. The ability of these organometallic compounds to inhibit the enzymatic activity of the serine esterases acetyl‐ and butyrylcholinesterase was investigated. It appeared that the new ferrocenyl phosphonates inhibited both enzymes by competitive, mixed or non competitve mechanisms with inhibition constants in the range 35–1000 µM. Both compounds also behave as slow time‐dependent inactivators of butyrylcholinesterase. The presence of the ferrocenyl entity seems then to have a dramatic effect on the biochemical behavior of the systems. Copyright © 2010 John Wiley & Sons, Ltd.     

Diastereoselective Double C−H Functionalization of Chiral Ferrocenes with Heteroaromatics

Diastereoselective double C−H heteroarylation of chiral ferrocenes provides valuable compounds with multiple functionalities using mild reaction conditions and simple reagents. Pd-Complexes with chiral mono-protected amino acids afforded corresponding heteroarylated ferrocenyl amines in good yields and high diastereomeric purities. In this way, a variety of indole, thiophene, pyrrole, or furan substituents were introduced to the ferrocene moiety. Furthermore, a range of relevant functional groups, for example ketone, ester, chloro, nitro, or silyl, are tolerated by this method. An alternative combination of amino acid and ferrocenyl amine configurations was leveraged to provide the complementary diastereomeric products. The products of C−H heteroarylation can be transformed into corresponding phosphines. Absolute configurations of CH-activation products were confirmed by the combination of X-ray crystallographic analysis and CD spectroscopy. ¹⁹F NMR kinetic study and DFT calculations provided insights into the reaction mechanism and reasons governing stereoinduction.     

Alkynylation of ferrocene by terminal alkynes. Part I. A simple one-step synthesis of ferrocenylacetylenes

Ferrocene reacts with terminal alkynes in the presence of copper and iron salts to give 1-ferrocenyl-2-R-alkynes (R - substituent). This direct cross-coupling of ferrocenyl and alkynyl moieties allows for the preparation of ferrocenyl substituted alkynes in one step directly from ferrocene and a terminal alkyne avoiding prior preparation of other derivatives of ferrocene. This new synthetic reaction does not require special conditions, is promoted by the action of common iron and copper salts, and tolerates the presence of functional groups in the alkyne.     

铑-ImiFerroPhos配合物对β-取代-α,β-不饱和磷酸酯的不对称氢化

将手性二茂铁双膦配体ImiFerroPhos应用到β-取代-α,β-不饱和磷酸酯的不对称氢化反应中,在温和的反应条件下,以高收率及较高对映选择性合成了一系列β-取代的手性磷酸酯,最高获得了92%的ee值.     

Effects of ferrocenyl group on refractive index of colloidal crystal system formed by polymer-grafted silica in organic solvent

Colloidal crystallization of copolymer-grafted silica containing ferrocenyl groups in organic solvents and effects of ferrocenyl groups on effective refractive index of colloidal crystal systems were investigated. Poly(ferrocenyl metharylate (FeMA)-co-methyl methacrylate (MMA)-grafted silica gave colloidal crystallization in dimethylformamide and acetonitrile. The colloidal crystals exhibited characteristic coloration due to cooperative effects of specific absorption at 400–500 nm by ferrocenyl group and transmission of 700–800-nm light through the crystals. It was observed that effective refractive index of colloidal crystals systems of poly(FeMA-co-MMA)-grafted silica was higher than that of poly(MMA)-grafted silica. Normalized effective refractive index of the system linearly increased with mole fraction of FeMA in grafted copolymer. However, poly(FeMA-block-MMA) did not bring effective increase of the index because of bias formation of ferrocenyl group on silica.     

Direct SN1 reaction at oxidized PPF surfaces

For comparative purposes, two series of pyrolyzed photoresist film (PPF) substrates are prepared with and without reductive conditions, i.e. in the presence and absence of H₂. Electrochemical and X-ray photoelectron spectroscopy analyses show that PPF substrates prepared in the absence of H₂ possess many more surface oxygen functional groups, mostly hydroxyl groups, than PPF prepared under reductive conditions. These oxidized PPF samples can be advantageously involved in an SN₁ reaction to covalently bind ferrocenyl groups to the surface as (sub-)monolayers.     

Friedel-Crafts acylation of ferrocene with alkynoic acids

Ferrocene reacts with alkynoic acids (conjugated or nonconjugated terminal), trifluoroacetic anhydride and triflic acid (or boron trifluoride etherate) to afford the corresponding ferrocenyl ynones in good yields. Only in the case of propynoic- and 3-butynoic acid complex, untreatable reaction mixtures were obtained. However, propynoilferrocene was obtained by desilylation of (trimethylsilyl)propynoilferrocene with KF/18-crown-6. Reaction with nonconjugated terminal alkynoic acids, carried out in the presence of a large excess of triflic acid (4 equiv.) results in formation of complex mixtures of products (in the reaction with 4-pentynoic acid enol triflate of ferrocenyl 1,4-diketone and 2-ferrocenyl-5-methylfuran were isolated). Ferrocenyl ynones obtained in this work can be used for synthesis of more complex ferrocenyl systems by “click” chemistry.     

Synthesis of ferrocenyl conjugates of thio analogs of hydroxyl-containing biomolecules via the Mitsunobu reaction with N-(ethoxycarbonyl)ferrocenecarbothioamide as the pronucleophile

A new method for attachment of a ferrocenyl moiety to hydroxyl-containing biomolecules is reported, based on the Mitsunobu reaction with N-(ethoxycarbonyl)ferrocenecarbothioamide. The reaction results in the replacement of the OH group with a (ferrocenyl)thioimidoyl moiety. Using this method, ferrocenyl conjugates of cholesterol, stigmasterol, as well as protected and nonprotected adenosine and 2′-deoxy adenosine were obtained in high yield and with high chemo- and stereoselectivity.     

热开环聚合制备高分子量二茂铁基聚二甲基硅烷及其与四氰基乙烯生成电荷转移络合物的研究

主链含有过渡金属元素的聚合物由于其具有独特的结构和性能 ,长期以来一直受到学术界和工业界的高度关注[1～3] .通常这类聚合物的合成是采用不同单体间的缩聚方法来制备的[4] ,所得到的聚合物往往分子量较低如数千 ,因而这类聚合物的实用性较差 .近来 ,Ｍａｎｎｅｒｓ等人采用开环聚合法合成了结构单元中含有二茂铁夹心结构的高分子量二茂铁基聚硅烷[5] ,使得这类化合物向实用性方面前进了一大步 .高分子磁性材料由于其质轻、易于加工、保磁性强和易于回收利用等特点 ,以及在电子仪器、传感器、仪表、通讯和自动控制等领域的广泛应用前景 ,…     

Unusual Racemization of Tertiary P-Chiral Ferrocenyl Phosphines

Tertiary phosphines are generally known to withstand inversion under moderate conditions. In this work, a remarkable racemization process of three P-chiral ferrocenyl phosphines is reported. Subjected to conventional column chromatography as highly enantioenriched compounds, they greatly experienced racemization when collected at the column outlet within minutes. Initially, attention was drawn to this unusual inversion behavior after observing that the superb enantiomeric excess of these ligands (>95 % ee in all cases) was almost lost in their corresponding ruthenium(II) complexes. Successively excluding possible racemization causes, these P-chiral ferrocenyl phosphines were found to undergo a significant, acid-catalyzed racemization process at room temperature within a few minutes. This process is mainly observed during standard column chromatography by using conventional silica or alumina, but can also be triggered deliberately by addition of certain acids. Therefore, the stereochemical preservation of P-chiral phosphines during their purification may per se not always be guaranteed, since column chromatography is the most frequently used technique for purifying such types of compounds.