Cope rearrangement of 9-methylenebarbaralane. Complete line shape analysis

Greifenstein, Linda G.; Lambert, Joseph B.; Broadhurst, Michael J.; Paquette, Leo A.

doi:10.1021/jo00946a032

Cited by 18 publications

(8 citation statements)

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“…Our model gives a reasonable explanation for the two main effects leading to the rate acceleration found by Evans and Golob [4] and summarized by Bunnage and Nicolaou [8]: a) the degree of alkoxide-metal dissociation, with a maximum acceleration obtained with a more naked anion and b) the amount of added [18]crown-6 as a ionophore in that the degree of ion pairing should influence the thermochemical cycle in Fig. 7.…”

Section: Methodssupporting

confidence: 75%

“…Bunnage and Nicolaou [8] recently summarized two different effects by which the rate acceleration of the oxy-Cope reaction might be modulated: a) by the degree of alkoxide-metal dissociation, with a maximum acceleration obtained with a more naked anion, and b) by the addition of [18]crown-6 as a ionophore. These two effects are merely different aspects of the same thing, i.e.…”

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confidence: 99%

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Density Functional Study of the Oxy-Cope Rearrangement

Baumann¹,

Chen²

2001

HCA

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With the goal of explaining the very large rate acceleration in the anion-assisted Cope rearrangement, the behavior of the prototypes of the Cope rearrangements, namely hexa-1,5-diene (4), hexa-1,5-dien-3-ol (5), and the oxy anion 6 of the latter were compared. For this purpose, two-dimensional DFT (hybrid B3LYP functionals with 6-31G* basis set) potential-energy surfaces (PESs) were computed, based on two interatomic distances. As the reliability of DFT/B3LYP-computed energies can not be taken for granted, we first performed model computations on the experimentally well-studied bridged homotropylidenes 1 ± 3. Then, the transition states of the Cope rearrangements of 3-methylhexa-1,5-dien-3-ol (7), (2Z,4Z,7Z)-cyclonona-2,4,7-trien-1-ol (9), 1-methoxy-2-endo-vinylbicyclo[2.2.2]oct-5-en-2-exo-ol (11), and (1S,2R)-2-hydroxy-1-methyl-2-vinylbicyclo[4.4.0]dec-6-en-8-one (arbitrary numbering; 13) and of their oxy anions 8, 10, 12, and 14, respectively, were computed by the same method. These examples were chosen because kinetic data have been measured for most of them (except for 13 and 14) and/or because they furnished already important contributions to the discussion of the character of the Cope rearrangement. The computation of DG = for a given temperature allowed to calculate the rate constants at that temperature for the different rearrangements and to compare them with the experimental data. In the cases of the neutral and anionic oxy-Cope rearrangements, the equation DDG = 2.3026´RT´DpK a suggested a correlation between the difference in the pK a values of the pair of reactants and the pair of transition states and the change of the two free energies of activation.

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Section: Methodssupporting

confidence: 75%

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confidence: 99%

Density Functional Study of the Oxy-Cope Rearrangement

Baumann¹,

Chen²

2001

HCA

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“…It was observed that appearances of peaks changed in their NMR spectra at different temperatures due to dynamic rotation [14][15][16] and equilibrium [17][18][19] such as cope rearrangements. NMR data and X-ray crystallographic analysis of compound 6 are consistent with the proposed structure.…”

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confidence: 99%

Aromatisation in Adducts of α-Terpinene: Influence of Hindered Internal Rotations

Kaya

Şengül

Menzek

et al. 2011

Journal of Chemical Research

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Each adduct of α-terpinene with p-quinone and 1,4-naphthoquinone in Ac 2 O/Et 3 N at 180 °C gives two aromatic products, one of which had a distinctive smell formed by the loss of an ethylene group. Here, we report the crystal structure of (1RS, 4RS)-1-isopropyl-4-methyl-1,4-dihydro-1,4-ethanoanthracene-9,10-diyl diacetate. It is crystallised in an orthorhombic space group, Pbca, with cell dimensions a = 10.2899 (7), b = 19.7804(9), c = 19.7519(8) Å and Z = 8. According to its NMR and X-ray diffraction data, the isopropyl and acetate groups slowly rotate.

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“…Ethyl (2iZ*,3S*)-2,3-Dideuterio-2-hydroxy-3-(phenylseleno)propanoate (4). A solution of diisobutylaluminum phenylselenide in hexane was prepared by the addition of 1.32 g (4.25 mmol) of diphenyl selenide to 6.0 mL of a 1.41 M solution (8.5 mmol) of diisobutylaluminum hydride in hexane.…”

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confidence: 99%

“…The mixture was washed with phosphate buffer (pH 3), and the aqueous layer was back-extracted with three portions of CH2C12. The combined organic layers were washed with saturated aqueous NaHC03, dried, and concentrated, and the crude product was purified by chromatography (ether/hexane, 1:1) to give 4: 1.5 g (64% yield); IR 3560, 1730, 1480, 1080, 905 cm'1; NMR 1.19 (t, 3 ,J = 7.1), 3.14 (s, 1), 3.33 (s, 1), 3.97 (dq, 1, J = 7.13, 7.15), 4.12 (dq, 1, J = 7.09, 7.14), 7.2-7.6 (m, 5). Anal.…”

mentioning

confidence: 99%