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Oxygen-17 nuclear magnetic resonance spectroscopy of organosulfur compounds. Part III. Oxygen-17 NMR lanthanide-induced shifts (LIS) of diastereotopic oxygen atoms in trans-2-[alkyl(aryl)sulfonyl]cyclohexanols

By Thomas A. Powers and Slayton A. Evans, Jr.
Published in Heteroatatom Chemistry (1992), 3(1), 41-50

Abstract: The ¹⁷O NMR diastereotopicity or chemical shift
differences of diastereotopic sulfonyl oxygens in the title compounds (shown at right; R = methyl, propyl, phenyl, benzyl, or t-butyl) have been determined. From a comparison of their sulfonyl oxygen ¹⁷O NMR lanthanide-induced shifts, equilibrium distributions between diastereomeric sulfonyl oxygen-Eu(fod)₃ complexes were determined and found to be sensitive to both the steric size of the SO₂R substituent as well as the proximity of the C-1 hydroxyl group.

Oxygen-17 nuclear magnetic resonance spectroscopy of organosulfur compounds. 2. ¹⁷O NMR lanthanide-induced shifts (LIS) of diastereotopic sulfonyl oxygens in substituted six-membered-ring sulfones

By T.A. Powers; Slayton A. Evans, Jr.; K. Pandiarajan; and J.C.N. Benny
Published in The Journal of Organic Chemistry (1991), 56(19), 5589-94

Abstract: The ¹⁷O NMR shifts of diastereotopic sulfonyl oxygens within a series of conformationally homogeneous six-membered-ring organosulfur compdounds have been determined. Their lanthanide-induced shifts, resulting from competitive complexation with the europium metal ion [i.e., (Eu(FOD)₃], provide structural insights into the relative binding potential of the attached diastereotopic sulfonyl oxygens.

Oxygen-17 NMR studies of heterocyclic sulfones and trans-2-(alkylsulfonyl)cyclohexanols utilizing the lanthanide shift reagent Eu(FOD)₃

By Thomas A. Powers; Lee G. Pedersen; and Slayton A. Evans, Jr.
Published in Phosphorus, Sulfur, Silicon, and the Related Elements (1991), 59(1-4), 499-504

Abstract: Complexes between paramagnetic metal ions and sulfones bearing diastereotopic oxygens are examined through ¹⁷O NMR spectroscopy of heterocyclic sulfones and trans-2-(alkylsulfonyl)cyclohexanols in the presence of Eu(FOD)₃, as well as through ab initio calculations on Lithium complexes of 3,4-epoxythiolane 1,1-dioxide.

Lanthanide induced oxygen-17 NMR shifts of diastereotopic oxygen atoms in 1-thiadecalin 1,1-dioxide and related compounds

By Thomas A. Powers and Slayton A. Evans, Jr.
Published in Tetrahedron Letters (1990), 31(41), 5835-8

Abstract: Lanthanide-induced ¹⁷O NMR shifts of diastereotopic sulfonyl oxygens in 1-thiadecalin 1,1-dioxides (shown at left; X = CH₂, O, or S) provide a basis for determining equilibrium constants between diastereomeric Ln-sulfone complexes.

Electrochemical reduction of (1-bromo-2,2-dimethylpropyl)benzene in dimethylformamide on carbon electrodes

By Albert J. Fry and Thomas A. Powers
Published in The Journal of Organic Chemistry (1987), 52(12), 2498-501

Abstract: Products from the electrochemical reduction of PhCHBrCMe₃ on carbon electrodes in DMF containing lithium perchlorate depended upon the electrolysis potential. At relatively positive potentials the products are derived primarily from the coupling of two benzylic radicals, as shown in Scheme 1:

Scheme 1

At more negative potentials the products are derived from the corresponding carbanions, as shown in Scheme 2:

Scheme 2

This establishes for the first time the mechanism of bibenzyl formation in the electrochemical reduction of benzyl bromides at nonmetallic electrodes. The meso-dL ratios of the 1,2-di-tert-butyl-1,2-diphenylethane products are dependent upon electrolysis potential; head-to-head coupling of ^.CH(CMe₃)Ph is sterically restricted.

Electrochemical behavior of layered annulenes

By Albert J. Fry; Thomas A. Powers; Klaus Muellen; and Wolfgang Irmen
Published in Tetrahedron Letters (1985), 26(40), 4879-82

Abstract: Reduction potentials of [14]annulenes (I; n = 3-5; II, III) were determined by cyclic voltammetry. The voltammograms of I (n = 3, 4) exhibit clear evidence of electronic interaction between the 2 pi systems.