Conformational analysis. 35. S-Alkylthianium salts

Eliel, Ernest L.; Willer, Rodney L.

doi:10.1021/ja00448a040

Cited by 35 publications

(10 citation statements)

References 5 publications

(7 reference statements)

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“…These amounted to 12.2 and 14.0 Hz for 26 and 2c, respectively, in agreement with the experimental evidence of Fava and co-workers for relevant S-methylthionium cations (14). The question of the relative thermodynamic stabilities of the equatorial (2b) and the axial (2c) epimers was answered by submitting each isomer to conditions of equilibration in acetonitrile-p'3 at 1 10°C for 1 week according to a previously established protocol (13). The ratio of epimers was monitored by nrnr, using the relative peak intensities of the S-methyl groups at 2.86 (axial) and 2.76 ppm (equatorial) as the reference peaks.…”

Section: ----supporting

confidence: 81%

“…The relevant chemical shift assignments were made by 2D-homoconelation and 2D-heterocorrelation nmr and the results compared with those previously reported for the case of 2H-tetrahydrothiapyran and the corresponding isomeric Smethyl salts (13). An axial S-methyl induces a smaller downfield shift (@-interaction) at the @-carbons than an equatorial S-methyl.…”

Section: ----mentioning

confidence: 93%

“…The configuration of the S-methyl groups of the two sulfonium salts was assigned unambiguously by I3C nmr spectroscopy as based on well-known precedents (13). The relevant chemical shift assignments were made by 2D-homoconelation and 2D-heterocorrelation nmr and the results compared with those previously reported for the case of 2H-tetrahydrothiapyran and the corresponding isomeric Smethyl salts (13).…”

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confidence: 93%

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Thionium analogs of the opiates levorphanol and isolevorphanol: synthesis of the 17-deaza-17-thia isosteres (sulforphanol and isosulforphanol)

Belleau¹,

Gulini²,

Camicioli³

et al. 1986

Can. J. Chem.

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The total synthesis of the position-17 sulfur analogs of the perchlorate salts of the morphinans, (±)-levorphanol and (±)-isolevorphanol via4a-(2-aminoethyl)-1,2,3,4,4a,9-hexahydro-6-methoxyphenanthrene, a key intermediate in the synthesis of butorphanol (4), is described. 2D-Correlation and heterocorrelation nuclear magnetic resonance spectroscopy confirmed the configurational relationship of the isosteres.

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confidence: 81%

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confidence: 93%

Section: ----mentioning

confidence: 93%

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Thionium analogs of the opiates levorphanol and isolevorphanol: synthesis of the 17-deaza-17-thia isosteres (sulforphanol and isosulforphanol)

Belleau¹,

Gulini²,

Camicioli³

et al. 1986

Can. J. Chem.

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“…In the three equatorial 2-ethylthiacyclohexanes there is one gauche interaction in 11c and its enantiomer, one 51,52 (in solution, the entropy and enthalpic terms must be considered 40,41 ). In conformer 11c, the C(7)-H b to C(2)-H ax and C(3)-H eq to C(7)-H ax distances are 2.498 and 2.388 Å , respectfully.…”

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confidence: 99%

Molecular orbital study of the conformational energies (−ΔG° orA values) of 2-alkyltetrahydro-2H-thiopyrans (tetrahydrothiopyrans, thiacyclohexanes, thianes)

Freeman

Phornvoranunt

Hehre

1999

J. Phys. Org. Chem.

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Ab initio 6-31G* and MP2/6-31G*// 6-31G* methods and density functional (pBPDN**) theory were used to calculate the geometries and relative energies of the chair, boat, and twist-boat conformations of tetrahydro-2H-thiopyrans (tetrahydrothiopyrans, thiacyclohexanes, thianes). The chair conformation of thiacyclohexane is 5.3 and 8.0 kcal mol À1, respectively, (1 kcal = 4.184 kJ) more stable than the twist-boat and boat structures at the MP2/6-31G*// 6-31G* level. Ab initio methods were used to calculate the relative energies of the rotamers in the chair conformations of 2-alkylthiacyclohexanes (CH 3 , C 2 H 5 , i-C 3 H 7 , t-C 4 H 9 , neo-C 5 H 11 , SiMe 3 ). The MP2/6-31G*// 6-31G* conformational energies (ÀDG°or A values, kcal mol À1 ) of the 2-alkylthiacyclohexanes (Me = 1.00; Et = 1.16; i-Pr = 1.02; t-Bu = 3.56; neo-Pent = 1.04; SiMe 3 = 2.05) are smaller than those calculated for the corresponding alkylcyclohexanes and 4-alkylthiacyclohexanes. Plots of the calculated conformational energies (ÀDG°) for the 2-alkylthiacyclohexanes versus the calculated conformational energies for the corresponding alkylcyclohexanes are linear (slope = 0.680 and r = 0.983 for 6-31G* and slope = 0.667 and r = 0.989 for MP2/6-31G*// 6-31G*). The C(2)-S(1) bond lengths are in the range 1.827-1.840 Å and the C(6)-S(1) bond lengths are in the range 1.815-1.819 Å . With the exception of the axial 2-t-Bu substituent (103.0°), the C-S-C angles vary from 98.6°to 100.4°. The S(1)-C(2)-C(7) angle in the most stable axial conformer is larger that the corresponding angle in its most stable equatorial conformer.

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“…The position of the N-H and N-CH 3 moieties in various piperidines was evaluated. 31,32 Lowtemperature 13 C NMR was used to analyze conformational equilibria in various thianes, 33 oxanes, 34 thianium salts, 35 and piperidines and piperdinium salts. 36 This work is fundamental to the understanding of the chemistry of conformationally mobile six-membered saturated heterocyclic rings, found in many natural products as well as synthetic materials.`I have always tried to explain things in written publications lucidly.…”

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confidence: 99%

Ernest L. Eliel: A life of purpose, determination, and integrity

Seeman

2002

Chirality

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A concise biography of Ernest L. Eliel is presented. The highlights of Eliel's scientific achievements are described, beginning with his Ph.D. thesis research performed under the supervision of Professor Harold Snyder (University of Illinois) and continuing as a faculty member at Notre Dame (synthesis of nonracemic C(6)H(5)CHDCH(3); kinetic method of conformational analysis; equilibrium and NMR methods of conformational analysis); and at the University of North Carolina (conformational analysis of heterocyclic compounds; enantioselective synthesis). Eliel's professional career as a teacher, textbook author, and major figure in the American Chemical Society are discussed. His philosophies of life, science, and chemistry are described by a series of poignant quotations.

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Conformational analysis. 35. S-Alkylthianium salts

Cited by 35 publications

References 5 publications

Thionium analogs of the opiates levorphanol and isolevorphanol: synthesis of the 17-deaza-17-thia isosteres (sulforphanol and isosulforphanol)

Thionium analogs of the opiates levorphanol and isolevorphanol: synthesis of the 17-deaza-17-thia isosteres (sulforphanol and isosulforphanol)

Molecular orbital study of the conformational energies (−ΔG° orA values) of 2-alkyltetrahydro-2H-thiopyrans (tetrahydrothiopyrans, thiacyclohexanes, thianes)

Ernest L. Eliel: A life of purpose, determination, and integrity

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