Ferrocene chemistry

The mechanism of Friedel-Crafts acylation is believed to involve ratedetermining exo attack of the acylating species generating an intermediate 11, analogous to the Wheland intermediates generated during electrophilic substitution of arenes. Rapid loss of a proton from 11 results in formation of the neutral product 7.  

The five-membered cyclopentadienyl rings of ferrocene are relatively electron rich, such that acylation takes place at a rate 10 times faster than for benzene, 

CautionI All procedures should be carried out in an efficient fume hood. Eye protection must be worn at all times. 

Ensure that the stirrer bar and glassware are clean, and that they have been dried thoroughly in an oven at 120°C for 2 h. 

Add ferrocene (20.0 g, 0.108 mol) to the 250 ml round-bottomed flask and dissolve with stirring in dry dichloromethane (90 mL). 

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A62. A. N. Nesmeyanov, "Khimiya ferrotsena. Nauka, Moscow, 1969. Collection of 127 of the author s published papers on ferrocene chemistry. 

As the latter were not easily accessible by chemical synthesis at that time, new methods of preparing these ferrocene derivatives were developed and introduced in 1969. It was then proved that the U-4CRs of chiral a-ferrocenyl-alkylamines can form diastereomeric a-aminoacid derivatives stereo-selectively, and it was further shown that after the reaction the a-ferrocenyl groups of the products can be replaced by protons, thus resynthesizing the chiral a-ferrocenyl-alkylamines simultaneously." Later, the development of this ferrocene chemistry was given up since such syntheses cannot form the products in sufficient quantity and stereoselective purity. ... 

Planar chirality is a valuable feature of the ferrocene chemistry (Chart 2B,C) (205). This unnatural chirality type has attracted attention of several groups. Sadeghi and co-workers have demonstrated that the planar chiral ferrocenes are recognized by cytochrome c peroxidase (206). The rate constants for the oxidation of R and S enantiomers by the wild type enzyme equal 2.9 x 106 and 1.6 x 106 M 1 s respectively. Interestingly, the enantioselectivity inverts for the aspartate 34 for lysine mutant and the rate constants become equal to 5.9 x 106 and 14.8 x 106 M-1 s-1, respectively. The discrimination of planar chiral ferrocenes is the case, but the stereoselectivity factors are lower than 3. 

The Mannich reaction is a particularly good method of introducing a reactive functional group into a sensitive aromatic nucleus. The reaction has been very useful in ferrocene chemistry. Treatment of chromium acetylacetonate under Mannich conditions yielded a tris-V,N-dimethylaminomethyl chelate (XXXIII). This remarkable substance was very difficult to purify because of its extreme solubility in all solvents ranging from n-heptane to water. The trisamino chelate (XXXIII) is a deep purple, hydroscopic oil and behaves like a typical organic amine. Reaction of this amine with methyl iodide afforded a trisquater-nary ammonium salt (XXXIV), soluble in water but insoluble in organic solvents. When this salt (XXXIV) was treated with cyanide ion, trimethylamine was lost and the cyanomethyl chelate (XXXV) was formed. 

Much work has been undertaken to modify electrode surfaces with films which are themselves conducting. The most promising approaches involve organic charge transfer and radical ion polymers. Coordination chemistry has, to date, played little part in this work (a good recent review is available),67 but one example relating to ferrocene chemistry can be quoted. In this example a well known electron acceptor, 7,7, 8,8 -tetracyanoquinodimethane (TCNQ 27), is modified and incorporated into polymer (28) in which the iron(II) of the ferrocene unit is the electron donor. The electrical conductivity of such a film will depend on partial electron transfer between ion and TCNQ centres as well as on the stacking of the polymer chains. The chemistry of other materials, based on coordination compounds, which have enhanced electrical conductivity is covered in Chapter 61. 

This work provides synthetic routes into polymeric-organometallic NLO materials based on some new and exciting ferrocene chemistry. Electric poling and SHG studies on these new materials will allow us to contrast the relative effectiveness of the two approaches (i.e. pendant versus main-chain). 

For a modem account of ferrocene chemistry, see Ferrocenes (Eds. A. Togni, T. Hayashi), VCH, Weinheim, 1995. 

Aside from intercalators, a number of other tethered electroactive moieties can provide added functionality to nucleic acids. These moieties are often based on ferrocene chemistry [180-182] but others derived from quinones [176,183,184] have also emerged. Additionally, derivatives with altered linker and ancillary groups are used to make the functionalized nucleic acids electro chemically distinguishable [185-188], and thus compatible with identification methodologies that rely upon detection of sequence variants. Whilst some efforts have been directed at solid phase synthetic routes for probe production, others have focussed on construction of electroactive nucleotides ( electrotides ) compatible with enzymatic methods of incorporation into nucleic acids (Fig. 4). 

Chemistry as a Basis for Chemical Computer Programs. I. Ugi, Intra-Sci. Chem. Rep., 5,229 (1971). The Potential of Four Component Condensations for Peptide Syntheses—A Study in Isonitrile and Ferrocene Chemistry as well as Stereochemistry and Logics of Syntheses. 

The discovery of ferrocene and the establishment of its structure in the 1950s mark the beginning of modem organometallic chemistry. Today ferrocene chemistry is ubiquitous, and numerous significant applications are to be found in the areas of homogenous catalysis, asymmetric... 

Breakdown (by Journal) of References Quoted in Organometallic Chemistry Reviews, Section B (Ferrocene Chemistry)... 

Japan. Symp. on ferrocene chemistry, see also refs. 25.7, 25.9... 

One fascinating aspect of ferrocene chemistry is its extraordinary ability to stabilize carbocations that formally should have their positive charge in a position adjacent to the cyclopentadienyl ring (a-ferrocenylalkyl carbocations). Such cations are so stable that they form quantitatively from appropriate precursors (e.g., alcohols) on treatment with acid and many of them remain unchanged in solution for days and... 

Ugi, I. Potential of four component condensations for peptide syntheses. Study in isonitrile and ferrocene chemistry as well as stereochemistry and logics of syntheses. Intra-Science Chemistry Reports 1971,5, 229-261. 

P.L. Pauson (1993) Organo-iron compounds in Chemistry of Iron, ed. J. Silver, Blackie Academic, Glasgow, p. 73 -A good summary of ferrocene chemistry and of other organo-iron complexes. 

However, there is no single-volume source available delineating ferrocene chemistry and its applications. 

For a discussion of ferrocene chemistry from a stereochemical point of view, see the classical ... 

One of the key tasks of the advanced organic chemistry is to find direct routes for C-H functionalization of aromatic compounds, thus avoiding incorporation of halogen or other functionalities in order to correspond the principles of green chemistry. It is nicely illustrated by the example taken from ferrocene chemistry. Indeed, the lithium derivative of ferrocene proved to react smoothly with pyrazine... 

Additional specific examples are from the ferrocene chemistry, where the huge progress has been achieved thanks to the Imrie s group results [85]. The ligandless palladium(II) acetate-based method in the presence of barium hydroxide as the base has been proved as a convenient procedure for producing arylferrocenes from the iodoferrocene as the starting material. For example, 4-formylphenyl ferrocene (303)... 

Several mechanistic studies in ferrocene chemistry have been... 

A useful intermediate in ferrocene chemistry is the stable salt, a-ferrocenyl-carbonium tetrafluoroborate, readily obtained from a-ferrocenylcarbinols [Eq. (67) (Allenmark, 1974)]. 

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