Der gezielte Aufbau von Biarylverbindungen: Moderne Konzepte und Strategien

Bringmann, Gerhard; Walter, Rainer; Weirich, Ralf

doi:10.1002/ange.19901020906

Cited by 140 publications

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References 142 publications

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“…[4][5][6] Moreover, 1,1'-bi-2-naphthol (BINOL) often serves as the starting material for obtaining various chiral binaphthyl compounds. [7] An optically pure 1,1'-binaphthyl molecule can adopt two different conformations, either cisoid or transoid, for which the torsion angle between the two naphthalene rings is either smaller or larger than 908, respectively. The circular dichroism (CD) spectra of both conformations have been shown to be almost mirror images of each other.…”

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confidence: 99%

A Vibrational Raman Optical Activity Study of 1,1′‐Binaphthyl Derivatives

Liégeois

2009

ChemPhysChem

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The Raman polarized and vibrational Raman optical activity (VROA) backward spectra are simulated for a series of 2,2'-substituted 1,1'-binaphthyl compounds presenting a variety of torsion angles between the two naphthalene rings. The substitution prevents free rotation along this torsion angle and the chirality of these compounds is thus called atropisomerism. However, the rotation is not completely frozen so that two different conformations, namely cisoid and transoid, are found and their Raman and VROA signatures are studied. As expected, the Raman spectra are not very sensitive whereas the VROA spectra present more complex patterns, which evolve as a function of the torsion angle between the two naphthalene groups. In particular, our analysis shows that some modes can be used as a probe for the determination of the torsion angle of these molecules in solution. The contributions of both invariants to the VROA backward intensity are also assessed.

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confidence: 99%

A Vibrational Raman Optical Activity Study of 1,1′‐Binaphthyl Derivatives

Liégeois

2009

ChemPhysChem

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“…The attempts to dimerize the tetrahydroxanthenones 2 with oxidizing agents like [K 3 Fe(CN) 6 ], FeCl 3 ·6H 2 O, Cu(OH)Cl·TMEDA and (tBu) 2 O 2 failed. Besides decomposition, we got isomerization of the double bond (Table 1, compound 6).…”

Section: Resultsmentioning

confidence: 97%

Probing the Oxidation of Functionalized (Hexahydro)xanthenols

2009

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“…4 b and 4c arise from reductive ring-opening reaction of the still, "axially prostere~genic"~~) lactone-type biaryl 3, which is obtained by an intramolecular aryl coupling 14) of the ester-type prefixed molecular moieties. As reported previously'), the two rotational isomers 4b and 4c can be separated unusually readily from each other -far better than the corresponding methyl compounds (e. g. than 1 b and 1 c), which may be interpreted by a closer proximity of the two functional groups (OH and NBn) in 4c ("syn") than in the less rapidly eluting isomer 4b ("anti").…”

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Acetogenic isoquinoline alkaloids, XXI. An atropisomer‐differentiating reaction for the chemical analysis of axial chirality and its computational investigation: Proof of the stereostructure of dioncophylline A

1991

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A chemical method for the unambiguous elucidation of axial chirality in naphthylisoquinoline alkaloids such as dioncophylline A (la) is described. It involves synthetic connection of the stereogenic axis to be investigated with the stereocenters present in the same molecule. The resulting macrocyclic ansa compound ?c is formed in high yield, yet exclusively for only one of the two atropodiastereomers (4c), the other isomer (4b) does not cyclize at all. This cyclization behavior fully confirms the stereostructure l a of dioncophylline A, as postulated by us earlier. For an interpretation of the striking atropisomer specificity of this ring closure reaction, computerassisted theoretical investigations on the molecular geometries and thus thermodynamical properties of both of the imaginable cyclization products ? b/c have been performed by using force-field (MM2, MMX) and semiempirical methods (AM1). The optimized structures show the obtained macrocycle ?c to be a nonstrained, stable compound, whereas the other possible product ?b (which definitely is not formed) should be severely distorted.Dioncophylline A*) (previously "triphy~phylline"~)) is one of the major alkaloid^^-^) isolated from the carnivorous ' ) tropical liana Triphyophyllum peltatum. For this interesting naphthylisoquinoline alkaloid, Bruneton et al. 3s) have proposed the gross structure 1, correctly establishing the relative configuration at C-1 and C-3 as trans, but incorrectly assigning the absolute configuration to be 1S,3S, and with complete neglect of the stereochemistry at the biaryl linkage, which gives rise to additional, rotational isomerism.We have recently isolated, structurally reinvestigated2), and synthesized 8, dioncophylline A, and could finally establish the complete stereostructure of this alkaloid as 1 a. The constitution and the relalive configuration at the stereogenic centers (C-1 and C-3) could be confirmed mainly by NMR evidence'), and according to our first total synthesis8) the absolute configuration clearly proved to be 1R,3R. The absolute configuration at the biaryl linkage could be established') by application of the exciton split chirality method'), namely from the positive sign of the first Cotton effect of the fully aromatic naphthylisoquinoline 2a obtained by 0-methylation of 1 a and subsequent dehydrogenation under mild conditions.With respect to the many structures of naphthylisoquinoline alkaloids") that are not sufficiently established, or even obviously wrong, we wished to look for additional, independent procedures for the reliable elucidation of the

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Der gezielte Aufbau von Biarylverbindungen: Moderne Konzepte und Strategien

Cited by 140 publications

References 142 publications

A Vibrational Raman Optical Activity Study of 1,1′‐Binaphthyl Derivatives

A Vibrational Raman Optical Activity Study of 1,1′‐Binaphthyl Derivatives

Probing the Oxidation of Functionalized (Hexahydro)xanthenols

Acetogenic isoquinoline alkaloids, XXI. An atropisomer‐differentiating reaction for the chemical analysis of axial chirality and its computational investigation: Proof of the stereostructure of dioncophylline A

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