Solution-state conformations of 2-fluoro-, 2-chloro- and 2-bromo-acetophenone: a dipole moment and kerr effect study

Mirarchi, D.; Ritchie, G. L. D.

doi:10.1016/0022-2860(84)87226-9

Cited by 6 publications

(3 citation statements)

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“…Various 2′-substituted acetophenones were synthesized, and conformational studies were performed. 7 Among the studies, Schaefer examined TS-coupling of 2-fluoro and 2,6-fluoroacetophenones based on calculations, 3d but that work has received relatively little attention, although the results are extremely significant.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, we deduced that compounds 1a and 1b prefer s - trans conformations to cis conformations (Figure ), suggesting that the fluorine atoms control the conformation of the compound. Various 2′-substituted acetophenones were synthesized, and conformational studies were performed . Among the studies, Schaefer examined TS-coupling of 2-fluoro and 2,6-fluoroacetophenones based on calculations, but that work has received relatively little attention, although the results are extremely significant.…”

Section: Introductionmentioning

confidence: 99%

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Conformational Preference of 2′-Fluoro-Substituted Acetophenone Derivatives Revealed by Through-Space ¹H–¹⁹F and ¹³C–¹⁹F Spin–Spin Couplings

et al. 2021

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The conformational properties of 2′-fluoro-substituted acetophenone derivatives were elucidated based on H α –F and C α –F through-space spin–spin couplings (TS-couplings), which occur between two atoms constrained at a distance smaller than the sum of their van der Waals radii. This study revealed that 2′-fluoro-substituted acetophenone derivatives in solutions form exclusively s - trans conformers by analyzing their NMR spectra focused on the TS-couplings. The magnitudes of the coupling constants 5 J (H α , F) and 4 J (C α , F) correlate linearly with the value of the dielectric constant of the solvents. Furthermore, s - trans conformations of the two derivatives were confirmed by X-ray crystallographic analysis. These conformational preferences were consistent with the DFT calculations. The s - cis conformer, in which fluorine and oxygen atoms lie in a syn -periplanar mode, may be subject to strong repulsion between the two polar atoms and become unstable. The s - trans preference of the 2′-fluoro-substituted acetophenone derivatives may be utilized in drug design.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Conformational Preference of 2′-Fluoro-Substituted Acetophenone Derivatives Revealed by Through-Space ¹H–¹⁹F and ¹³C–¹⁹F Spin–Spin Couplings

et al. 2021

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“…5b , Case 2). 2-Bromophenyl, mesityl, and 2-chloro-3-pyridyl groups are all expected to be substantially rotated out of conjugation with the ketones to which they are attached 27 - 29 rendering them highly sterically hindered toward nucleophilic attack, as illustrated in transition state 35b . By contrast, 2-methoxybenzoyl and ortho -unsubstituted phenyl groups are conjugated, 30 and this allows an unhindered approach of the allyl group as in transition state 34b .…”

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confidence: 99%

Direct and highly regioselective and enantioselective allylation of β-diketones

Chalifoux

Reznik

Leighton

2012

Nature

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The enantioselective allylation of ketones represents both a problem of fundamental importance in asymmetric reaction design and one of only a very small number of available methods to access valuable tertiary carbinols. Despite the vast amount of attention from chemists that this problem has elicited,1-8 however, success has generally been limited to just a few simple ketone types thus limiting the utility of these methods. A method for the selective allylation of functionally complex ketones would be expected to increase the utility of ketone allylation methods in the chemical synthesis of important targets. Here we describe the operationally simple, direct, regioselective, and enantioselective allylation of β-diketones. The strong tendency of β-diketones to act as nucleophilic species was overcome by the co-optation of their enol form to provide the necessary Brønsted acid activation. This unprecedented reaction thus not only significantly expands the pool of enantiomerically enriched and functionally complex tertiary carbinols that may be easily accessed, but also overturns more than a century of received wisdom regarding the reactivity of β-diketones.

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Fluorine deshielding in the proximity of a methyl group. An experimental and theoretical study

Gribble

Keavy

Olson

et al. 1991

Magnetic Reson in Chemistry

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I9F chemical shifts are reported for a series of alkyl-substituted fluoronaphthalenes and related compounds that exhibit steric crowding around the fluorine atom due to the proximity of methyl groups. Comparisons of these chemical shifts with others measured in similar compounds but without the corresponding methyl groups sbow that this crowding effect produces a large low-field shift of the I9F signal. Similar effects, hut with an even larger sensitivity to the steric crowding, were recently reported for "0 chemical shifts. The electronic origin for this proximity effect on I9F chemical shifts is analyzed within the molecular orbital theory, at the INDO level, using the inner projections of the polarization propagator technique. It is found that the presence of the methyl group produces an increase in the absolute value of the paramagnetic term of the magnetic shielding constant.

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Solution-state conformations of 2-fluoro-, 2-chloro- and 2-bromo-acetophenone: a dipole moment and kerr effect study

Cited by 6 publications

References 20 publications

Conformational Preference of 2′-Fluoro-Substituted Acetophenone Derivatives Revealed by Through-Space ¹H–¹⁹F and ¹³C–¹⁹F Spin–Spin Couplings

Conformational Preference of 2′-Fluoro-Substituted Acetophenone Derivatives Revealed by Through-Space ¹H–¹⁹F and ¹³C–¹⁹F Spin–Spin Couplings

Direct and highly regioselective and enantioselective allylation of β-diketones

Fluorine deshielding in the proximity of a methyl group. An experimental and theoretical study

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Solution-state conformations of 2-fluoro-, 2-chloro- and 2-bromo-acetophenone: a dipole moment and kerr effect study

Cited by 6 publications

References 20 publications

Conformational Preference of 2′-Fluoro-Substituted Acetophenone Derivatives Revealed by Through-Space 1H–19F and 13C–19F Spin–Spin Couplings

Conformational Preference of 2′-Fluoro-Substituted Acetophenone Derivatives Revealed by Through-Space 1H–19F and 13C–19F Spin–Spin Couplings

Direct and highly regioselective and enantioselective allylation of β-diketones

Fluorine deshielding in the proximity of a methyl group. An experimental and theoretical study

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Product

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Conformational Preference of 2′-Fluoro-Substituted Acetophenone Derivatives Revealed by Through-Space ¹H–¹⁹F and ¹³C–¹⁹F Spin–Spin Couplings

Conformational Preference of 2′-Fluoro-Substituted Acetophenone Derivatives Revealed by Through-Space ¹H–¹⁹F and ¹³C–¹⁹F Spin–Spin Couplings