Metallic complexes, chirality

Although the chiral recognition mechanism of these cyclodexttin-based phases is not entirely understood, thermodynamic and column capacity studies indicate that the analytes may interact with the functionalized cyclodextrins by either associating with the outside or mouth of the cyclodextrin, or by forming a more traditional inclusion complex with the cyclodextrin (122). As in the case of the metal-complex chiral stationary phase, configuration assignment is generally not possible in the absence of pure chiral standards. 

Asymmetric allylic substitutions are widely applied in organic synthesis, using various metal complexes, chiral ligands, nucleophiles and allyl systems [39]. Although Pd is often the metal of choice, this is not the case for monosubstituted allylic substrates, where most Pd catalysts predominantly produce the achiral linear product. In contrast. Mo, W and Ir catalysts preferentially give rise to the desired branched products and, in recent years, a number of very effective Ir catalysts for various substrates have been developed [40]. Since, to the best of our... 

I.I.I.3.4.2. Alkylation of Other Acyl-Metal Complexes Chiral Cobait-Acyl Complexes... 

Related Alkylations of Chiral a-Alkoxy Vinyl-Metal Complexes Chiral a-Alkoxy Vinyl-Iron Complexes... 

TABLE 2. Asymmetric autocatalysis initiated by various organic and metal complex chiral initiators... 

Pieraccini, S., Gottarelli, G., Mariani, P., Masiero, S., Saturni, L., Spada, G. P., Columnar lyomesophases formed in hydrocarbon solvents by chiral lipophilic guanosine-alkali metal complexes. Chirality 200, 13, 7-12. 

Supramolecular Metal Complexes Chiral Self-Assembled Supramolecular Helicates Since the first introduction of the term helicate by Lehn et al. in 1987,58 there have been a number of investigations of self-assembled supramolecules with... 

Reaction of [FeCp(C6Me6)][PF6] [33-35] with excess KOH (or tBuOK) in THF or DME and excess alkyl iodide, allyl bromide, or benzyl bromide leads to one-pot hexasubstitution (Scheme 5a) [36-38]. With allyl bromide (or iodide) in DME, the hexaallylated complex has been isolated and its X-ray crystal structure determined, but the extremely bulky dodeca-allylation [52] product can also be reached when the reaction time is extended to two weeks at 40 °C. The chains are fixed in a directionality such that conversion to the enantiomer is not possible, thus making the metal complex chiral (Scheme 5b). 

The area covered is very widespread and the role of the calixarene molecules reach from a simple platform or skeleton on which to assemble chiral centers to an inherent part of the chiral structure. Biologically active molecules or derivatives are involved as well as artificial ligands and their metal complexes. Chiral calixarenes have been used as stationary phases in analytical separations or as host molecules in sensors. Basic properties of calixarenes, such as their conformational stabilities, have been studied with chiral derivatives as well as more... 

Type IV When the solute is part of a diastereomeric metal complex (chiral ligand-exchange chromatography)... 

It is remarkable that the allyl group (as allyl bromide or iodide) is the only one leading to complete double branching of the C6Mc6 complex. CpFe+-induced dodecaallylation of C6Mc6 indeed gives the extremely bulky dodeca-allylation product that can be reached when the reaction is prolonged for two weeks at 40°C. The chains are blocked in a directionality that cannot convert into its enantiomer and makes the metal complex chiral (Scheme 11.2). Both the hexa- and dodeca-allylation reactions are well controlled.12... 

In this chapter, we reviewed recent developments regarding lithium, sodium, and potassium salt based-catalysis, with a particular focus on asymmetric catalysts. While these alkali-metal salts have traditionally been used as simple bases, recent advances based on chiral multifunctional acid-base combination chemistry, using chiral crown-alkali-metal complexes, chiral lanthanoid/alkali-metal complexes, chiral alkali-metal alkoxides, and chiral alkali-metal phosphates, have also been outstanding. These synergic acid-base catalyst systems should enable more efficient and/or new transformations that have not been possible thus far using conventional catalysts that only rely on Lewis acidity or Bronsted/Lewis basicity. 

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