Planar-chirality

The reductive couphng of the chiral planar di(imine) 42, prepared from the corresponding chiral (il)-dialdehyde, in turn available as a single enantiomer by standard reactions, can lead to four stereoisomers. The use of... [Pg.9]

In 2005, Carretero et al. reported a second example of chiral catalysts based on S/P-coordination employed in the catalysis of the enantioselective Diels-Alder reaction, namely palladium complexes of chiral planar l-phosphino-2-sulfenylferrocenes (Fesulphos). This new family of chiral ligands afforded, in the presence of PdCl2, high enantioselectivities of up to 95% ee, in the asymmetric Diels-Alder reaction of cyclopentadiene with A-acryloyl-l,3-oxazolidin-2-one (Scheme 5.17). The S/P-bidentate character of the Fesulphos ligands has been proved by X-ray diffraction analysis of several metal complexes. When the reaction was performed in the presence of the corresponding copper-chelates, a lower and opposite enantioselectivity was obtained. This difference of results was explained by the geometry of the palladium (square-planar) and copper (tetrahedral) complexes. [Pg.198]

Planar Chirality. Planar chirality arises from the desymmetrization of a symmetric plane in such a way that chirality depends on a distinction between the two sides of the plane and on the pattern of the three determining groups. In the definition of this chiral system, the first step is the selection of a chiral plane the second step is to identify a preferred side of the plane. The chiral plane is the plane that contains the highest number of atoms in the molecule. [Pg.14]

Figure 18.17. Ferrocene-based chiral-planar P-N ligand, and phosphinooxazolines [32]...

Scheme 6 Fu s chiral planar ferrocenyl 4-DMAP catalyzed KR of sec-allylic alcohols [82]...

FIGURE 5.16 Examples of chiral planar complexes (a) cyclometallate ferrocene-Pt, (b) [PtCl3(lra i-2-butene)], and (c) [(meio-stilbenediamine)(isobutyldiamine)Pt]2 +. ... [Pg.155]

Figure 3.35 Synthesis of a chiral planar oxazoline functionalised carbene featuring a [2,2]-...

Helicity (screw sense) is a (geometric) structural property, by which the arrangement of atoms in molecules can be described as a combined rotation and translation process. Centro-chiral, planar-chiral molecules can be considered also as helical, having in mind their spatial environment (helicity around a point, a plane or an axis). In numerous cases, the understanding of chiral structures under the aspect of helicity is advantageous. [Pg.10]

Fig. 8. Interdependence of centrochirality, axial chirality, planar chirality and helicity (schematic illustration)...

The cross coupling reactions of aryl halides or aryl triflates with arylmetals catalysed by palladium(O) has found extensive use in the synthesis of unsymmetrical biaryls (ref. 27). A recent application of this coupling approach in the presence of chiral planar chromium complexes (ref. 25) has proved fruitful in the synthesis of chiral biaryls. Furthermore, Cr(CO)3-complexed biaryls can be isomerised under thermodynamic control, providing access to both atropisomers. Heating a solution of the complexed biaryl 37 in xylene under reflux resulted in a 1 99 ratio favouring the isomerised biaryl chromium complex 38 (ref. 28)... [Pg.413]

This reaction has been extended to the translocation of the acyl group for indole derivatives. In addition, a chiral planar DMAP derivative has been developed and applied for the enantioselective rearrangement of 0-acylated azlactone and the same catalyst recently has been used for an intermolecular reaction to form 1,3-diketones. Moreover, 3-(2,2,2-triphenyl-1 -acetoxyethyl)-4-(dimethylamino) pyridine (TADMAP) has been applied as a chiral nucleophilic catalyst to catalyze the carboxyl migration of oxazolyl, furanyl, and benzofuranyl enol carbonates with good to excellent levels of enantioselec-tivity. The rearrangement for oxazole derivatives are particularly efficient for giving chiral lactams and lactones. ... [Pg.417]

The development of a vast number of chiral ligands has been the key aspect in the development of the field. The potential for variation of these ligands is almost endless by variation of the donor atoms and the ligand backbone. Bidentate chiral ligands which possess central chirality, planar chirality and axial chirality have aU been applied in a range of transformations. The most eflfective donor atoms in these ligands are P,P, N,N and P,N systems [28]. [Pg.65]

Ferrocenes become chiral upon attachment of a chiral unit to the ferrocene system or by intrinsic chirality (planar chirality) arising from the substitution pattern of ferrocenes as in 6-8. [Pg.11]

Carretero et al. already found that Pd(II) and Cu(I) complexes of P,S-bidentate ligands, especially those having a bulky substitution of sulfur, have provided very high asymmetric inductions. Recently, they have reported that Pd(II) complexes of chiral planar (R)-l-phosphino-2-sulfenylferrocenes (Fesulphos ligands) (62) act as effective Lewis acids for highly enantioselective Diels-Alder reaction (Scheme 16.19)... [Pg.342]

Finally, all three types of chirality were claimed to occur in the first optically pure planar-chiral cyclopentadienyl cobalt complex 329, which uniquely contained three different types of chirality, planar, carbon-centered, and helical chirality (Figure 64). ... [Pg.76]

Fuji and co-workers were the first to design experiments that used this protocol and proposed two strategies for the establishment of conformationally chiral enolates axially chiral, planar chiral, or central chiral (Figure 1.35). [Pg.25]

Other racemates showing high a-values (>2.00) are Troger s base (2.64), l-(9-fluorenyl)ethanol (2.24), phenylthiohydantoin (PTH-Pro) (2.23), 2-phenylcycloheptanone (2.20), 7,8,9,10-tetrahydrobenzo[a]pyren-7-ol (2.04), and tra 5 -4-chlorostilbeneoxide (2.00). It should be noted that a-values of 7.92 are exceptional in chiral planar chromatography, whereas a-values exceeding 12 (ranging between 12.7 and 37) were previously obtained for six specific solutes on MCTA, BSA-silica, and (5)-A-(2-naphthyl)alanine-silica columns [16]. [Pg.70]

As other stationary phases used in chiral planar chromatography, 6-CD-bonded TLC plates were also prepared [52] after the success obtained by this chiral phase in column chromatography to resolve a large number of optical isomers [53,54]. [Pg.104]

Garcia Mancheno O, Gomez Arrayas R, Carretero J-C (2005) Palladium complexes of chiral planar l-phosphino-2-sulfenylferrocenes as efflcient catalysts in enantioselective Diels-Alder reactions. Organometallics 24 557-561... [Pg.145]

Le Roux E, Malacca R, Manoury E, Poli R, Gonsalvi L, Peruzzini M (2007) Highly efficient asymmetric hydrogenation of alkyl aryl ketones catalyzed by iridium complexes with chiral planar ferrocenyl phosphino-thioether ligands. Adv Synth Catal 349 309-313... [Pg.149]

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