Ferrocene chiral

Moyano A, Rosol M, Moreno RM, Lopez C, Maestro MA (2005) Oxazoline-mediated interannular cyclopalladation of ferrocene chiral palladium(II) catalysts for the enantioselective Azti-Claisen rearrangement. Angew Chem Int Ed 44 1865-1869... 

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... 

Gleichzeitig wurde vorgeschlagen 59), ferrocen-chirale Verbindungen unter planar-chirale Verbindungen (5) einzuordnen, da im Gegeiisatz zu... 

Scheme 7.44 Asymmetric addition of diphenylzinc to various aldehydes in the presence of 5 mol% of ferrocene chiral ligand, as described by Bolm and Muniz [68].

Turrin C-O, Chifffe J, de Montauzon D, Balavoine G, Manoury E, Caminade A-C, Majoral J-P (2002) Behavior of an optically active ferrocene chiral shell located within phosphorus-containing dendrimers. Organometallics 21 1891-1897... 

Appllca.tlons. The first widely appHcable Ic separation of enantiomeric metallocene compounds was demonstrated on P-CD bonded-phase columns. Thirteen enantiomeric derivatives of ferrocene, mthenocene, and osmocene were resolved (7). Retention data for several of these compounds are listed in Table 2, and Figure 2a shows the Ic separation of three metallocene enantiomeric pairs. P-Cyclodextrin bonded phases were used to resolve several racemic and diastereomeric 2,2-binaphthyldiyl crown ethers (9). These compounds do not contain a chiral carbon but stiU exist as enantiomers because of the staggered position of adjacent naphthyl rings, and a high degree of chiral recognition was attained for most of these compounds (9). 

Asymmetric catalysis using chiral ligands, including cyclic phosphine or pyra-zole fragments covalent-bonded with ferrocene system 98PAC1477. 

Chiral ferrocenes have received niucli attenlion as ligands in metal-calalyzed reactions [39], bul tiieir use in copper cliemislry has been very limited [40, 41]. Hie ferrocene moiety offers die possibility of utilizing botli central and planar cliirality in die ligand. By analogy witli tlie copper arenetiiiolales described above, ferrocenyl copper complex 33 iSclieme 8.20) is extremely inleresling. 

Recently a novel chiral ferrocene-based amidinato ligand and its rhodium complexes have been described. The chiral N,N -bis(ferrocenyl)-substituted formamidine (N,N -bis[(S)-2- (lR)-l-(diphenylphosphino)ethyl ferrocen-l-yl]for-mamidine was prepared from commercially available (IR)-l-(dimethylamino) ethyl ferrocene by a multistep procedure in an overall yield of 29%. Deprotonation of the ligand with -butyllithium followed by addition of [RhCl2(COD)2] as illustrated in Scheme 167 yielded the corresponding (formamidinato)rhodium(l)... 

The synthesis of the unsymmetrical imidazolium salt 11 bearing a planar-chiral ferrocene was described by Bolm starting from (Rp)-[2-(trimethysilyl)-ferrocenyl] methanol 12 which afforded the salt in good yield after reaction with Ar,M-carbonyl diimidazole and methylation (Scheme 9) [18]. 

Abstract The unique and readily tunable electronic and spatial characteristics of ferrocenes have been widely exploited in the field of asymmetric catalysis. The ferrocene moiety is not just an innocent steric element to create a three-dimensional chiral catalyst enviromnent. Instead, the Fe center can influence the catalytic process by electronic interaction with the catalytic site, if the latter is directly coimected to the sandwich core. Of increasing importance are also half sandwich complexes in which Fe is acting as a mild Lewis acid. Like ferrocene, half sandwich complexes are often relatively robust and readily accessible. This chapter highlights recent applications of ferrocene and half sandwich complexes in which the Fe center is essential for catalytic applications. 

Chiral Catalysts Electronically Influenced by a Ferrocene Core.152... 

Planar Chiral Ferrocenes as Lewis- or Br0nsted-Base Catalysts.163... 

Fig. 5 Definition of the stereodescriptors of planar chiral ferrocenes according to Schlogl...

Palladacycles are defined as compounds with a Pd-C CT-bond with the Pd being stabilized by one or two neutral donor atoms, typically forming 5- or 6-membered rings [51]. Ferrocenyl palladacycles constitute a particularly attractive catalyst class partly due to the element of planar chirality. The first diastereoselective cyclopallada-tion of a chiral ferrocene derivative was reported in 1979 by Sokolov [52, 53]. 

In 2005, Moyano et al. [60] reported a new type of chiral dimeric ferrocene palladacycle 43 that lacked the element of planar chirality and involved three... 

A related planar chiral Co-based oxazoline palladacycle COP-X (46) was later found to be of higher synthetic utility as it permitted the use of benzimidates, [62] as well as allylic trifluoro- [63] and trichloroacetimidates [64, 65]. 46 was found to be superior to its ferrocene analogue 41 [61] in a number of aspects such as ease of... 

In 1996, Fu et al. reported the S3mthesis of the planar chiral heterocycles 64, formally DMAP fused with a ferrocene core [82]. While the original synthesis provided racemic 64a in only 2% overall yield requiring a subsequent resolution by preparative HPLC on a chiral stationary phase, a recently improved synthesis furnished the racemic complexes 64 in 32-40% yield over seven steps. A subsequent resolution with di-p-toluoyltartaric or dibenzoyltartaric acid gave access to the enantiomers with >99% ee (28 14% yield for each isomer in this step) [83]. 

The [Fe-Cp]-fragment does not only play the role of an additional steric element introducing planar chirality into the otherwise flat pyridine system. Substitution at the pyridine 2-position usually cuts the nucleophilicity of the nitrogen atom thus limiting the possibilities to achieve efficient chirality transfer using nucleophilic pyridine catalysts [84]. Ferrocene, however, functions as a strong electron donor (see Sect. 1) and thus restores the nucleophilicity impaired by substitution. 

Extending the same concept of a planar chiral nucleophilic or basic heterocyclic Fe-sandwich complex, aza-ferrocenes 65 were prepared. The latter have also been successfully applied as bidentate ligands in transition metal catalysis [85]. 

Gomez Arrayas R, Adrio J, Carretero JC (2006) Recent applications of chiral ferrocene ligands in asymmetric catalysis. Angew Chem Int Ed 45 7674—7715 Dai LX, Hou XL (2010) Chiral ferrocenes in asymmetric catalysis. Wiley-VCH, Weinheim Rigaut S, Delville MH, Losada J, Astrac D (2002) Water-soluble mono- and star-shaped hexanuclear functional organoiron catalysts for nitrate and nitrite reduction in water syntheses and electroanalytical study. Inorg Chim Acta 334 225-242... 

Jautze S, Diethelm S, Frey W, Peters R (2009) Diastereoselective bis-cyclopalladation of ferrocene-1,1 -diyl bis-imidazolines translation of central via axial into planar chirality. Organometallics 28 2001-2004... 

Indeed, the advantages of using ferrocene as a scaffold for chiral... 

The first monosubstituted ferrocene derivatives containing chiral amino-sulfide backbones in the side chain were reported by Bonini et These... 

Togni and co-workers have used the convergent methodology to link phosphine-containing chiral ferrocene ligands on the cyclophosphazene core to obtain dendrimeric structures of the type 37 (Fig. 21) (201). The reaction with the cyclophosphazene end occurs by the replacement of the P-Cl bond and by the formation of the P-0 bond. The dendrimers contain twelve and sixteen ferrocene moieties respectively. The phosphine units present can coordinate to Rh(I) to afford metallic dendrimers, which have been shown to be excellent catalysts for the enantioselective hydrogenation of dimethyl itaconate. The product... 

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