Anti-selective reaction of .alpha.-sulfenyl acetals with silylated carbon nucleophiles. Scope, limitation, and mechanism

Kudo, Kazuaki; Hashimoto, Yukihiko; Sukegawa, Makoto; Hasegawa, Masaki; Saigo, Kazuhiko

doi:10.1021/jo00055a009

Cited by 26 publications

(11 citation statements)

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“…These reactions are better considered to proceed via open oxocarbenium ions such as 94 with the sulfur substituent aligned to maximize hyperconjugation with the cationic center. Additions to these cations by Felkin-Anh-like transition states [88][89][90] (favoring 94) [97,98] provide results that coincide with the conclusions presented for exocyclic oxocarbenium ions (Scheme 24). [77] Scheme 26.…”

Section: Acyclic Acetals Bearing Heteroatomssupporting

confidence: 76%

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Nucleophilic Substitution Reactions of 2‐Phenylthio‐Substituted Carbohydrate Acetals and Related Systems: Episulfonium Ions vs. Oxocarbenium Ions as Reactive Intermediates

2008

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A powerful approach for controlling the stereochemistry of glycosylation reactions involves using a directing group at an adjacent carbon to influence the stereochemistry of nucleophilic attack. The use of substituents such as I, PhS, and PhSe has proven to be especially valuable because it enables the preparation of 2‐deoxysugars after reductive removal of the directing group. The mechanisms of these reactions are generally considered to involve nucleophilic opening of bridged onium ions and to proceed with inversion. Onium ions, however, equilibrate with open cations, and these open forms can be favored when the cation is highly stabilized. Although the selectivities of reactions of carbohydrate‐derived cations are consistent with the intermediacy of onium ions, the reactions of acyclic cations are not. Instead, consideration of the preferred conformations of the oxocarbenium ions and stereoelectronically favored additions to these intermediates provides a predictive model to explain the diastereoselectivities observed in reactions of oxocarbenium ions bearing proximal heteroatoms.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

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Section: Acyclic Acetals Bearing Heteroatomssupporting

confidence: 76%

“…[97,98] For example, the substitution of acetal 91 formed ketone 92 preferentially (Scheme 26). Similar selectivities were observed with iodinesubstituted acetals (Scheme 27).…”

Section: Acyclic Acetals Bearing Heteroatomsmentioning

confidence: 99%

Nucleophilic Substitution Reactions of 2‐Phenylthio‐Substituted Carbohydrate Acetals and Related Systems: Episulfonium Ions vs. Oxocarbenium Ions as Reactive Intermediates

2008

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“…and extracted several times with Et 2 O. The combined extracts were dried (Na 2 SO 4 ) and evaporated in vacuo to give pure (S)-2-benzyloxy-1,1-dimethoxypropane (14; 1.6 g, 95%) [28], which was used in the next step without further purification.…”

Section: Experimental Partmentioning

confidence: 99%

Fate of the Oxygen Atoms in the Diol-Dehydratase-Catalyzed Dehydration ofmeso-Butane-2,3-diol

Speranza

Morelli

Orlandi

et al. 2001

HCA

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18 O-Substituted propane-1,2-diols and meso-butane-1,2-diols were synthesized and fed to growing cells of Lactobacillus brevis. Propan-1-ol and butan-2-ol, prepared from such diols through diol-dehydratase-catalyzed dehydration followed by intracellular reduction, were analyzed for their 18 O-content. For each propane-1,2-diol enantiomer, partial retention or complete loss of the isotope appeared to be related to the mode of substrate binding. Specific retention of the O-atom linked to the (R)-configured C-atom of meso-butane-1,2-diol indicates that the diol dehydratase handles this substrate like (R)-propane-1,2-diol.

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“…Neighboring-group participation is a widely used approach to control stereochemistry in substitution reactions of carbohydrate compounds. − Most commonly, acyloxy groups, namely, the acetate, benzoate, and pivaloate esters, ,, are used to favor the 1,2- trans products with high selectivity. ,, Neighboring-group participation has not emerged as a useful approach for controlling stereochemistry in reactions involving acyclic acetals, however. − The use of neighboring-group participation to control stereochemistry in acyclic systems, as illustrated in eq , would be significant because it would provide access to the products expected from nucleophilic additions to α-alkoxy aldehydes that would be governed by the Felkin–Anh or related − stereochemical models. Such transformations, however, often give products with modest diastereoselectivity. ,,− …”

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confidence: 99%

Using Neighboring-Group Participation for Acyclic Stereocontrol in Diastereoselective Substitution Reactions of Acetals

Ramdular

Woerpel

2020

Org. Lett.

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Neighboring-group participation of an ester enabled stereocontrol in substitution reactions of acyclic acetals. The ester group formed a trans-fused dioxolenium ion intermediate, which underwent a substitution reaction at the acetal carbon atom to afford the product with high diastereoselectivity. Neighboring-group participation was confirmed by isolating dioxolane products resulting from nucleophilic addition at C-2 of a 1,3-dioxolenium ion intermediate. Using a pivaloate ester as the participating group in combination with strong nucleophiles produced substitution products with diastereoselectivities of ≥90:10.

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Anti-selective reaction of .alpha.-sulfenyl acetals with silylated carbon nucleophiles. Scope, limitation, and mechanism

Cited by 26 publications

References 0 publications

Nucleophilic Substitution Reactions of 2‐Phenylthio‐Substituted Carbohydrate Acetals and Related Systems: Episulfonium Ions vs. Oxocarbenium Ions as Reactive Intermediates

Nucleophilic Substitution Reactions of 2‐Phenylthio‐Substituted Carbohydrate Acetals and Related Systems: Episulfonium Ions vs. Oxocarbenium Ions as Reactive Intermediates

Fate of the Oxygen Atoms in the Diol-Dehydratase-Catalyzed Dehydration ofmeso-Butane-2,3-diol

Using Neighboring-Group Participation for Acyclic Stereocontrol in Diastereoselective Substitution Reactions of Acetals

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