ChemInform Abstract: AXIAL PREFERENCE OF 2‐(1,3‐DITHIANYL)DIPHENYLPHOSPHINE OXIDE. A STRONG S‐C‐P ANOMERIC INTERACTION

Juaristi, Eusebio; Valle, Lucia; Mora-Uzeta, Coralia; Valenzuela, Bertha A.; Joseph‐Nathan, Pedro; Fredrich, M. F.

doi:10.1002/chin.198322281

Cited by 1 publication

(6 citation statements)

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“…This result is in contrast again with the strong axial preference of the 2-diphenylphosphinoyl group in 1,3-dithiane, AGO [2,31, and could be surprising because anomeric effects involving second-row elements have been predicted to be much less important than those with first-row elements [36].…”

Section: -Axial 22-equatorialcontrasting

confidence: 56%

“…0.8 ppm) chemical shift difference between axial and equatorial protons at C (4,6) [32]. This observation is important because finding AGadeq (H(4,6)) = 1.2 ppm in 1 led to the discovery of the strong S-C-P(0) anomeric effect [2].…”

Section: Evaluation Of the S-c-p(s) Anomeric Effectmentioning

confidence: 95%

“…Then, since anomeric effect = -AG'&.ic + AGEbserved (6) the magnitude of the anomeric effect would amount to 3.03 kcal/mol [9]. 2. It has been shown [12] that the AGO (2-tertbutyl) in 1,3-dithianes is about 60% of AGO (tertbutyl) in cyclohexane.…”

Section: -Axial 5-equatorialmentioning

confidence: 98%

“…This very acidic solvent is likely to transfer a proton to the phosphoryl oxygen, and the stability present in 1-ax is thereby evidently lost. It seems possible that protonation abolishes some electrostatic attractive interaction between the phosphoryl oxygen and the axial hydrogens in I-ax [2]. This argument has been advanced based on the nonbonded distances between the phosphoryl oxygen and the axial hydrogens H(4,6,,) in axial 1,3,5-trithiane 2-ax [7], and from the estimation of the attractive Coulombic interaction in I-ax [21].…”

Section: -Equatorialmentioning

confidence: 99%

“…Definitive proof for the conformation of 1 was obtained by single-crystal x-ray diffraction [2]. A perspective view of the molecular structure is shown in Figure 1.…”

Section: -Ax) Over 13-eq Reflects Nonetheless the Influence O F A Smentioning

confidence: 99%

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Second‐row anomeric interactions: The involvement of phosphorus

Juaristi

1990

Heteroatom Chemistry

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Proton NMR spectroscopy and x-ray crystallographic studies demonstrate the predominance of the axial conformer of 2-(diphenylphosphinoyl)-l,3-dithiane (1). Chemical equilibration of anancomeric models Spectroscopic evidence for the predominance of the equatorial conformers in 2-(diphenylphosphinoyl)-l,3-oxathiane (19) and 2-(diphenylphosphinoyl)-l,3-dioxane (22) was confirmed by the study of derivatives containing counterpoise substituents, or by chemical equilibration on anancomeric models. AD;Tc [P(0)Ph2] = -3.23 kcallmol was determined for the dioxane (chloroform solution), and AG& [P(O)PhJ

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Section: -Axial 22-equatorialcontrasting

confidence: 56%

Section: Evaluation Of the S-c-p(s) Anomeric Effectmentioning

confidence: 95%

Section: -Axial 5-equatorialmentioning

confidence: 98%

Section: -Equatorialmentioning

confidence: 99%

“…Definitive proof for the conformation of 1 was obtained by single-crystal x-ray diffraction [2]. A perspective view of the molecular structure is shown in Figure 1.…”

Section: -Ax) Over 13-eq Reflects Nonetheless the Influence O F A Smentioning

confidence: 99%

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