Disubstituted ferrocenes

Tellurium-lithium exchanges in the mono- and bis-telluroderivatives are a suitable route for the preparation of mono- and disubstituted ferrocenes. ... 

Bielawski et al. described the synthesis and properties of NHC 15 introducing a novel carbene architecture incorporating a l,l -disubstituted ferrocene moiety as backbone [71 ]. In its metal complexes [71,72] this carbene ligand supported a long-range electronic communication between the iron center and the carbene coordinated transition metal. 

Chiral ferrocenes form a class of powerful and useful chiral hgands, and a number of methods are available for their enantioselective synthesis. The introduction of a second substituent via directed metallation is a simple and powerful way to make disubstituted ferrocenes with planar chirality from simple, achiral monosubstituted ferrocenes. Chiral... 

Aminocarbonylation has also been applied to the synthesis of unsymmetrical ferrocene-1,1 -bis-carboxamides. Ferrocene-based chiral ligands are very useful in asymmetric catalysis, and enantiomerically pure ferrocenyl ligands can be obtained by optical resolution of unsymmetrically substituted ferrocenes. However, the synthesis of such unsymmetrical ferrocenes is not an easy task. The use of aminocarbonylation gave a solution to this challenge. For example, the Pd-catalyzed reaction of symmetrical ferrocenyl diiodide 144 with two different amines, morpholine and diethylamine (5 equiv. each) under 39.5 atm of CO, gave the desired unsymmetrically disubstituted ferrocene-biscarboxamide 145 in 85% yield (Equation (11)). ... 

Several generalizations are made on the basis of such data as in Table I. For instance, the two rings tend to absorb independently of one another10 that is, no conjugation of one ring to another. Nesmeyanov has also noted that while intensities of bands in the 220-600 m region increased from ferrocene to monosubstituted ferrocenes to heteroannularly disubstituted ferrocenes, the opposite is true in the 180-220 mjx region. 

For example, treatment of anion 21 with anhydrous FeCh gives the 1,T-disubstituted ferrocene 22 with a phosphaferrocenylmethyl group attached to each Cp ring (Scheme 1.5.9). Because the aldehyde employed was a racemic... 

Disubstituted acetylenes, polymerization, 11, 566 Disubstituted ferrocenes, properties, 12, 227 a,a -Disubstituted olefins, ethylene co-polymerization,... 

Ferrocene-containing co-polyesters, preparation, 12, 350 Ferrocene-containing liquid crystals dendrimers, 12, 235 disubstituted ferrocenes, 12, 227 hydrogen-bonded ferrocene derivatives, 12, 234 monosubstituted ferrocenes, 12, 222 polycatenar ferrocenes, 12, 234 properties, 12, 221... 

The presence or absence of the ion FeCsHjj" (tn/e 121) has been suggested (176) as a more sensitive criterion for distinguishing between homo- and heteroannularly disubstituted ferrocenes than the 9-10 /j. rule commonly... 

A considerable number of-1,2- and l,l -disubstituted ferrocenes have been investigated by Egger (58) and Egger and Falk (59), and a good correlation between mass spectra and stereochemistry has been found. The homonuclear disubstituted compounds (LXVIa), (LXVIb), and (LXVII) are thermally very sensitive, and their spectra differed only in the intensities of some of the fragments. 

The spectra of various disubstituted ferrocenes were examined by Clancy and Spilners (44) at low ionizing voltage, and they observed only the molecular ions. They have also used mass spectrometry to identify products from the reaction of lithioferrocene with benzyl chloride one of the products was dibenzylferrocene (189). The mass spectra of [5]-ferroceno-phanes show very intense molecular ion peaks and fragmentation is limited (9, 10). The ketone derivatives (LXXXT) and (LXXXII) fragment by elimination of carbonyl groups first. 

The first reported ferroceno heterocyclic compound of the type 1 was A-methyltetrahydropyridoferrocene (4). This compound was obtained from an anomalous Leuckart-Eschweiler-Clark reaction of 2-aminomethylferrocene (5 R = H), formaldehyde, and formic acid,4 although the structure 4 was not immediately recognized for this compound.5-8 The heterocyclic compound 4 can be used as an entry to 1,2-disubstituted ferrocenes since on reaction with potassium amide in liquid ammonia7 or with potassium hydroxide in methanol9 its... 

The 1,2-disubstituted ferrocene (13) on treatment with hydrochloric acid gives 14 which can be oxidized with manganese dioxide to give 15.9... 

The cyclic ether (25) has been prepared via the cyclization of 26 in monoglyme with potassium amide.14,15 The magnetic nonequivalence of the methylene group protons in 25 have been compared with other 1,2-disubstituted ferrocenes.16... 

Reaction of (2-methyl-5-)- and (2-methyl-6-benzothiazoIyl)-dimethyltriazene or 2-methyl-5- and 2-methyl-6-benzothiazolyl-diazonium salts with ferrocene gave 136 (R = ferrocenyl, R = H R = H, R = ferrocenyl, respectively).121 Use of the diazonium salts also led to the isolation of some 1,1 disubstituted ferrocenes in this reaction. The compounds 136 were used to prepare thiacyanines. Reaction of ferrocenecarboxaldehyde with the ethiodide of 2-methyI-benzothiazole followed by treatment with potassium iodide gave 137.121... 

As chiral ligands for transition metal complex-catalyzed asymmetric reactions, a variety of novel chiral ferrocenylchalcogen compounds, which possess a planar chirality due to the 1,2-unsymmetrically disubstituted ferrocene structure, have been prepared from chiral ferrocenes (Scheme 1). Thus, chiral diferrocenyl dichalcogenides bearing an optically active dimethylaminoethyl or p-tolyl-sulfoxide moiety 1-10 were prepared by lithiation of the corresponding chiral ferrocenes, highly diastereoselectively, in moderate to high chemical yields. 

The Hammett-Taft analysis of the redox potentials gave a good correlation using parameters. Also, the dependence was additive for the disubstituted ferrocenes,... 

Preliminary data are also available on mass spectral correlations of several mono- and l,r-disubstituted ferrocenes where no phenyl group intervened between the substituent and the ferrocene ring. Results of this study are tabulated in Table X. The weakening effect of the acetyl and acid groups on the substituted ring-iron bond is clearly demonstrated in the compounds... 

Ratio of [CjH4XFe] Peaks in the Mass Spectra OF Monosubstituted and 1,1 -Disubstituted Ferrocenes ... 

As suggested by Kuwana 38), substituent effects in disubstituted ferrocenes may be additive. This point was demonstrated by Gubin and co-workers 62) by the comparison of the observed potentials from dichromate oxidations of a series of l,T-symmetrical and unsymmetrical disubstituted ferrocenes with the calculated potential value from the equation... 

Infrared studies have shown dependence of the carbonyl absorption value of a series of heteroannularly disubstituted ferrocene carboxylic acids and their methyl ethers on changes in the substituent in the other ring. Nes-meyariov and co-workers (31) have detected a shift to lower frequencies of yc=o values with increasing electron donation. For example, the carbonyl absorption was observed to be 1704 cm for I -sulfuralfluoroferrocene-carboxylic acid, but when the substituent was a methyl or ferf-butyl the... 

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