The zero-point-average structure of bicyclo[3.1.0]hexane as determined by electron diffraction and microwave spectroscopy

Mastryukov, V. S.; Osina, E. L.; Vilkov, L. V.; Hilderbrandt, R. L.

doi:10.1021/ja00463a012

Cited by 51 publications

(13 citation statements)

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“…The chair conformers of these bicyclic rings contain two pairs of eclipsing interactions between a pseudoaxial C–H bond in the five-membered ring (as shown in Fig. 3, A for 4a ) and either an N + –R bond or a C–H bond at one of the ring junctions (not shown), as documented previously [27–29]. When C(4) is fluorinated, the so-called electrostatic gauche effect [30][31], i.e.…”

Section: Resultssupporting

confidence: 80%

Fluorine as a Regiocontrol Element in the Ring Opening of Bicyclic Aziridiniums

Lam

Houk²,

Cossy

et al. 2012

Helvetica Chimica Acta

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The origin of the variation in the regioselectivity of the nucleophilic ring-opening of a series of bicyclic aziridinium ions derived from N-alkylprolinols was investigated by quantum chemical computations (M06-2X/6-31+G(d,p)—SMD). These aziridiniums differ only in the degree and the stereochemistry of fluoro substitution at C(4). With the azide ion as nucleophile, the ratio of the piperidine to the pyrrolidine product was computed. An electrostatic gauche effect influences the conformation of the adjoining five-membered ring in the fluorinated bicyclic aziridinium. This controls the regioselectivity of the aziridinium ring-opening.

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Section: Resultssupporting

confidence: 80%

Fluorine as a Regiocontrol Element in the Ring Opening of Bicyclic Aziridiniums

Lam

Houk²,

Cossy

et al. 2012

Helvetica Chimica Acta

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show abstract

“…This gave the bicycle [3.1.0] structure of ( 16 ) and ( 17 ) as a flattened boat conformer with an angle of pucker ca 20°. This is in complete agreement with the results of both theoretical and experimental investigations of related compounds …”

Section: Geometriessupporting

confidence: 92%

¹H NMR Spectra. Part 28: Proton chemical shifts and couplings in three‐membered rings. A ring current model for cyclopropane and a novel dihedral angle dependence for ³J_HH couplings involving the epoxy proton

Abraham

Leonard

Tormena³

2012

Magnetic Reson in Chemistry

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The (1) H chemical shifts of selected three-membered ring compounds in CDCl(3) solvent were obtained. This allowed the determination of the substituent chemical shifts of the substituents in the three-membered rings and the long-range effect of these rings on the distant protons. The substituent chemical shifts of common substituents in the cyclopropane ring differ considerably from the same substituents in acyclic fragments and in cyclohexane and were modelled in terms of a three-bond (γ)-effect. For long-range protons (more than three bonds removed), the substituent effects of the cyclopropane ring were analysed in terms of the cyclopropane magnetic anisotropy and steric effect. The cyclopropane magnetic anisotropy (ring current) shift was modelled by (a) a single equivalent dipole perpendicular to and at the centre of the cyclopropane ring and (b) by three identical equivalent dipoles perpendicular to the ring placed at each carbon atom. Model (b) gave a more accurate description of the (1) H chemical shifts and was the selected model. After parameterization, the overall root mean square error for the dataset of 289 entries was 0.068 ppm. The anisotropic effects are significant for the cyclopropane protons (ca 1 ppm) but decrease rapidly with distance. The heterocyclic rings of oxirane, thiirane and aziridine do not possess a ring current. (3) J(HH) couplings of the epoxy ring proton with side-chain protons were obtained and shown to be dependent on both the H-C-C-H and H-C-C-O orientations. Both density functional theory calculations and a simple Karplus-type equation gave general agreement with the observed couplings (root mean square error 0.5 Hz over a 10-Hz range).

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“…Furthermore, electron diffraction microwave spectroscopy [3] and ab-initio calculations [4][5][6][7][8][9] confirmed the restricted presence of only the pseudoboat conformation. Specifically for the N and S thymidine analogues (compounds 17 and 75 in Schemes 12.2 and 12.11), quantum mechanical potential energy surfaces obtained after constraining a chosen target dihedral in 10 increments, and allowing the remaining degrees of freedom [except for c (252 ) and g (51 )] to optimize to the default tolerance showed that the pseudoboat conformation is indeed more stable [10] (Figure 12.2).…”

Section: Pseudoboat Versus Pseudochair Conformationsmentioning

confidence: 97%

The Properties of Locked Methanocarba Nucleosides in Biochemistry, Biotechnology, and Medicinal Chemistry

Márquez

2008

Modified Nucleosides

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The zero-point-average structure of bicyclo[3.1.0]hexane as determined by electron diffraction and microwave spectroscopy

Cited by 51 publications

References 3 publications

Fluorine as a Regiocontrol Element in the Ring Opening of Bicyclic Aziridiniums

Fluorine as a Regiocontrol Element in the Ring Opening of Bicyclic Aziridiniums

¹H NMR Spectra. Part 28: Proton chemical shifts and couplings in three‐membered rings. A ring current model for cyclopropane and a novel dihedral angle dependence for ³J_HH couplings involving the epoxy proton

The Properties of Locked Methanocarba Nucleosides in Biochemistry, Biotechnology, and Medicinal Chemistry

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The zero-point-average structure of bicyclo[3.1.0]hexane as determined by electron diffraction and microwave spectroscopy

Cited by 51 publications

References 3 publications

Fluorine as a Regiocontrol Element in the Ring Opening of Bicyclic Aziridiniums

Fluorine as a Regiocontrol Element in the Ring Opening of Bicyclic Aziridiniums

1H NMR Spectra. Part 28: Proton chemical shifts and couplings in three‐membered rings. A ring current model for cyclopropane and a novel dihedral angle dependence for 3JHH couplings involving the epoxy proton

The Properties of Locked Methanocarba Nucleosides in Biochemistry, Biotechnology, and Medicinal Chemistry

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¹H NMR Spectra. Part 28: Proton chemical shifts and couplings in three‐membered rings. A ring current model for cyclopropane and a novel dihedral angle dependence for ³J_HH couplings involving the epoxy proton