Novel route to racemization of sulfoxides

Modena, G.; Quintily, U.; Scorrano, Gianfranco

doi:10.1021/ja00756a036

Cited by 32 publications

(9 citation statements)

References 8 publications

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“…4b for CD spectroscopy of (S)- 18A and (R)- 18B ). Sulfoxide could racemize under 6 M HClO 4 40. Under the biorelevant acidic or basic conditions tested, there was no detectable sulfoxide racemization.…”

Section: Resultsmentioning

confidence: 87%

Chiral Sulfoxide-Induced Single Turn Peptide α-Helicity

Zhang

Jiang

et al. 2016

Sci Rep

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Inducing α-helicity through side-chain cross-linking is a strategy that has been pursued to improve peptide conformational rigidity and bio-availability. Here we describe the preparation of small peptides tethered to chiral sulfoxide-containing macrocyclic rings. Furthermore, a study of structure-activity relationships (SARs) disclosed properties with respect to ring size, sulfur position, oxidation state, and stereochemistry that show a propensity to induce α-helicity. Supporting data include circular dichroism spectroscopy (CD), NMR spectroscopy, and a single crystal X-ray structure for one such stabilized peptide. Finally, theoretical studies are presented to elucidate the effect of chiral sulfoxides in inducing backbone α-helicity.

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Section: Resultsmentioning

confidence: 87%

Chiral Sulfoxide-Induced Single Turn Peptide α-Helicity

Zhang

Jiang

et al. 2016

Sci Rep

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“…It had previously been demonstrated that selected enantiopure sulfoxides can undergo acid-catalyzed racemization of stereochemistry at sulfur 47 and it was believed that the proximal hydroxyl of 3a could play a role in directing a possible inversion of the sulfinyl configuration. The addition of a small amount of trifluoroacetic acid (TFA) brought about immediate changes in the 1 H NMR spectrum of the sample.…”

Section: Resultsmentioning

confidence: 99%

Unexpected reactions of Grignard reagents with selected β-carboalkoxy substituted sulfinate esters

et al. 2015

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A series of six-membered rings bearing cis oriented vicinal carboxylate and sulfinate esters were treated with Grignard reagents with the intention of transforming them to ␤-carboalkoxy substituted sulfoxides. The expected outcome did not transpire and instead the substrates demonstrated the capacity to accept 3 equiv. of organometallic agent in an uncontrollable manner. As such, the substrates possessing eclipsing carboxylate and sulfinate esters accepted two organic ligands at the carboxylate functionality and one at the sulfinyl group. When isomer mixtures of sterically encumbered sulfinate esters were reacted, a single sulfoxide stereochemistry resulted. A mechanism involving the intermediacy of a sulfurane is proposed to account for the experimental observations. Résumé : Une série de cycles à six membres portant des esters carboxyliques et sulfiniques vicinaux ont été traités avec des réactifs de Grignard dans le but de les transformer en ␤-carboalkoxy sulfoxydes substitués. Le résultat espéré n'a pas été obtenu et, au lieu de cela, les substrats ont montré une capacité à accepter trois équivalents d'agent organométallique de manière incontrôlable. En tant que tels, les substrats portant des esters carboxyliques et sulfiniques en position éclipsante ont accepté deux ligands organiques au niveau de la fonction carboxylate et un au niveau du groupe sulfinyl. La réaction de mélanges isomériques d'esters sulfiniques stériquement encombrés a débouché sur une seule stéréochimie du sulfoxyde. Un mécanisme impliquant l'intermédiaire d'un sulfurane est proposé, qui permet d'expliquer les observations expérimentales. [Traduit par la Rédaction]Mots-clés : réactif de Grignard, ester sulfinique, sulfoxyde, réaction d'addition, sulfurane.

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“…of sulfoxide this value decreased from 22 to 7 μS cm −1 after 24 h. At the same time, as reported in Table 1, longer reaction times did not guarantee any increase of the yield, when lower amounts of 4 were used, but a decrease of the enantiomeric purity of the sulfoxide was observed without affecting the enantioselectivity of the allylation. Even if (R)-methyl p-tolyl sulfoxide is reported to be configurationally stable and it gives inversion only at high temperature 21 or in the presence of acids, 22 the possibility to form tetracoordinate sulfurane species can lead to the loss of enantiomeric purity and deactivation of sulfoxide. 14b,15 Other studies are underway to investigate this fascinating behaviour that combines the chemistry of silicon and sulfur compounds in a unique fashion with important implications in a fundamental organic transformation like enantioselective allylation of aldehydes.…”

Section: Reaction Mechanismmentioning

confidence: 99%

Chiral sulfoxides in the enantioselective allylation of aldehydes with allyltrichlorosilane: a kinetic study

et al. 2012

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The mechanism of the allylation of aldehydes in the presence of allyltrichlorosilane employing the commercially available (R)-methyl p-tolyl sulfoxide as a Lewis base has been investigated. The combination of kinetic measurements, conductivity analysis and quantum chemical calculations indicates that the reaction proceeds through a dissociative pathway in which an octahedral cationic complex with two sulfoxides is involved. The lack of turnover is ascribed to the formation of neutral sulfurane derivatives.

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Novel route to racemization of sulfoxides

Cited by 32 publications

References 8 publications

Chiral Sulfoxide-Induced Single Turn Peptide α-Helicity

Chiral Sulfoxide-Induced Single Turn Peptide α-Helicity

Unexpected reactions of Grignard reagents with selected β-carboalkoxy substituted sulfinate esters

Chiral sulfoxides in the enantioselective allylation of aldehydes with allyltrichlorosilane: a kinetic study

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