Darstellung und Röntgenstrukturanalyse von Bicyclo‐[4.2.1]non‐3‐en‐2‐on‐Derivaten

Kraus, Wolfgang; Patzelt, Helmut; Sadlo, Horst; Sawitzki, Gisela; Schwinger, Gerhard

doi:10.1002/jlac.198119811010

Cited by 6 publications

(4 citation statements)

References 16 publications

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“…Assigning the outer and inner doublets of the asymmetric quartet to, respectively, the bromine ±3/2 and ±1/2 states, and taking D and χ to be positive, we obtained the following estimates for the relevant (average) parameters: D ‘ = D − Δ J /3 = 964 Hz, J = −200 Hz, = 117.25 ppm, χ = 405 MHz with R = χ/ν Br = 5.2. These results are quite reasonable; the chemical shift is nearly the same as in solution (116.87 ppm), and the J and χ values are comparable to those determined for similar bromine compounds. , If we assume that r C - Br is as in the related compound methyl-4-bromo-5-oxobicyclo[4.2.1]non-3-ene-1-carboxylate (1.91 Å) we can estimate an average value for D (1128 Hz) and from this and D ‘ calculate Δ J to be 492 Hz. This is probably the least accurate result, because it is calculated as a (small) difference of relatively large numbers.…”

Section: Resultssupporting

confidence: 70%

“…These results are quite reasonable; the chemical shift is nearly the same as in solution (116.87 ppm), and the J and χ values are comparable to those determined for similar bromine compounds. 17,19 If we assume that r C-Br is as in the related compound methyl-4-bromo-5-oxobicyclo[4.2.1]non-3-ene-1-carboxylate (1.91 Å) 21 we can estimate an average value for D (1128 Hz) and from this and D′ calculate ∆J to be 492 Hz. This is probably the least accurate result, because it is calculated as a (small) difference of relatively large numbers.…”

Section: Resultsmentioning

confidence: 99%

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Bond Shift Rearrangement of Chloro-, Bromo-, and Iodobullvalene in the Solid State and in Solution. A Carbon-13 and Proton NMR Study

et al. 1998

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The mechanisms of the Cope rearrangement in chloro-, bromo-, and iodobullvalene in solution and in the solid state were investigated by NMR techniques. The dominant species in solution, for all three compounds, are isomers 2 and 3 with nearly equal concentrations (where the numbers refer to the substituted carbons in the bullvalene moiety). The kinetics of the rearrangement processes as studied by 1H and 13C NMR involve three dominant bond shift rearrangements: interconversion between isomers 2 and 3, degenerate rearrangement of isomer 2, and a pseudodegenerate rearrangement of isomer 3, with isomer 1 serving as an intermediate. The solid state properties of these compounds were studied by carbon-13 MAS NMR and the bromo and iodo derivatives also by X-ray crystallography. Bromo- and iodobullvalene crystallize entirely as isomer 2 in the orthorhombic Fdd2 space group. The molecules in the crystals are orientationally disordered, and the carbon-13 results show that this disorder is dynamic on the NMR time scale. Rotor-synchronized two-dimension exchange spectroscopy, magnetization transfer experiments, and analysis of dynamic MAS spectra show that the mechanism of the dynamic disorder involves a degenerate rearrangement of isomer 2 which results in an effective π-flip of the molecule in the crystal. The Arrhenius activation parameters for this process are ΔE † = 57.1 kJ/mol, A = 5.2 × 1012 s-1 for bromobullvalene and ΔE † = 58.5 kJ/mol, A = 1.8 × 1013 s-1 for iodobullvalene. Chlorobullvalene is liquid at room temperature (mp 14 °C). Upon cooling of this compound in the MAS probe to well below 0 °C, signals due to both isomer 2 and isomer 3 are observed in the solid state. It is not known whether the solid so obtained is a frozen glass, a mixture of crystals due to, respectively, isomer 2 and isomer 3, or a single type of crystals consisting of a stoichiometric mixture of both isomers. Rotor-synchronized two-dimensional exchange measurements show that the chlorobullvalene isomers in this solid undergo Cope rearrangement. However, the bond shift processes involve only a degenerate rearrangement of isomer 2 and a pseudodegenerate rearrangement of isomer 3. No cross-peaks corresponding to interconversion between the two isomers are observed.

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Section: Resultssupporting

confidence: 70%

Section: Resultsmentioning

confidence: 99%

Bond Shift Rearrangement of Chloro-, Bromo-, and Iodobullvalene in the Solid State and in Solution. A Carbon-13 and Proton NMR Study

et al. 1998

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“…The aldehyde 18 was isolated as its acetal 19 (Scheme 1), as it is known to be susceptible to an intramolecular aldol reaction. [49] Methyl vinyl ketone (20) as an additional Michael acceptor was examined and reacted with good enantioselectivity [Eq. (6)].…”

Section: Resultsmentioning

confidence: 99%

Non‐Biaryl Atropisomers in Organocatalysis

Brandes

Niess

Bella

et al. 2006

Chemistry A European J

217

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A new class of 6'-hydroxy cinchona alkaloids, with a non-biaryl atropisomeric functionalisation at position 5' of the quinoline core can be prepared by an easy amination procedure. These are the first derivatives for which the principle of atropisomerism is engrafted in the classical core of the cinchona alkaloids. The aminated cinchona alkaloids are effective organocatalysts for the Michael addition of beta-keto esters to acrolein and methyl vinyl ketone, in up to 93 % ee (ee=enantiomeric excess), as well as for the asymmetric Friedel-Crafts amination of a variety of 2-naphthols, permitting the preparation of the latter in up to 98 % ee. The aminated 8-amino-2-naphthol itself is the first chiral organocatalyst based on non-biaryl atropisomerism. The two enantiomers of this chiral primary amine can be used for the direct alpha-fluorination of alpha-branched aldehydes. The fluorinated compounds can thereby be accessed in up to 90 % ee.

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“…This leaching of vanadium may be the result of strong coordination by the donors to the surface vanadium species, thus preventing smooth reactions . In the reaction of 1a with acrolein ( 2e ), sequential intramolecular 1,2-addition reaction and acetylation proceeded to give 4-acetoxy-8-oxobicyclo[3.2.1]-octan-1-carboxylic acid ethyl ester ( 3f ) (Scheme ) 1 …”

Section: Resultsmentioning

confidence: 99%

Highly Efficient C−C Bond-Forming Reactions in Aqueous Media Catalyzed by Monomeric Vanadate Species in an Apatite Framework

et al. 2006

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A calcium vanadate apatite (VAp), in which PO4(3-) of hydroxyapatite (HAP), Ca10(PO4)6(OH)2, is completely substituted by VO4(3-) in the apatite framework, was synthesized. Physicochemical analysis of the VAp reveals the presence of isolated VO4 tetrahedron units with a pentavalent oxidation state. The VAp acts as a high-performance heterogeneous base catalyst for various carbon-carbon bond-forming reactions such as Michael and aldol reactions in aqueous media and the H-D exchange reactions using deuterium oxide. For example, a 200-mmol-scale Michael reaction under triphasic conditions proceeded rapidly, with an extremely high turnover number of up to 260 400 and an excellent turnover frequency of 48 s(-1). No vanadium leaching was detected during the above reactions, and the catalyst was readily recycled with no loss of activity.

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Darstellung und Röntgenstrukturanalyse von Bicyclo‐[4.2.1]non‐3‐en‐2‐on‐Derivaten

Cited by 6 publications

References 16 publications

Bond Shift Rearrangement of Chloro-, Bromo-, and Iodobullvalene in the Solid State and in Solution. A Carbon-13 and Proton NMR Study

Bond Shift Rearrangement of Chloro-, Bromo-, and Iodobullvalene in the Solid State and in Solution. A Carbon-13 and Proton NMR Study

Non‐Biaryl Atropisomers in Organocatalysis

Highly Efficient C−C Bond-Forming Reactions in Aqueous Media Catalyzed by Monomeric Vanadate Species in an Apatite Framework

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