The generation of C-glycosides through the enolate Claisen rearrangement

1979 ◽  
Vol 57 (13) ◽  
pp. 1743-1745 ◽  
Author(s):  
Robert E. Ireland ◽  
Craig S. Wilcox ◽  
Suvit Thaisrivongs ◽  
Noel R. Vanier
Keyword(s):  
Carboxylic Acids ◽  
Claisen Rearrangement ◽  
Sigmatropic Rearrangements ◽  
Unsaturated Carboxylic Acids ◽  
Aliphatic Esters ◽  
Ketene Acetals ◽  
Silyl Ketene Acetals

The [3,3]-sigmatropic rearrangements of silyl ketene acetals obtained from aliphatic esters of furanoid and pyranoid glycals is described. The heterocyclic γ,δ-unsaturated carboxylic acids II are produced in good yields. A new preparation of furanoid and pyranoid glycals is described.

scholarly journals Why do thioureas and squaramides slow down the Ireland–Claisen rearrangement?

2019 ◽  
Vol 15 ◽  
pp. 2948-2957
Author(s):  
Dominika Krištofíková ◽  
Juraj Filo ◽  
Mária Mečiarová ◽  
Radovan Šebesta
Keyword(s):  
Hydrogen Bond ◽  
Dft Calculations ◽  
Claisen Rearrangement ◽  
Green Solvents ◽  
Activation Barriers ◽  
Catalyst Free ◽  
Uncatalyzed Reaction ◽  
Transition Structures ◽  
Ketene Acetals ◽  
Silyl Ketene Acetals

A range of chiral hydrogen-bond-donating organocatalysts was tested in the Ireland–Claisen rearrangement of silyl ketene acetals. None of these organocatalysts was able to impart any enantioselectivity on the rearrangements. Furthermore, these organocatalysts slowed down the Ireland–Claisen rearrangement in comparison to an uncatalyzed reaction. The catalyst-free reaction proceeded well in green solvents or without any solvent. DFT calculations showed that the activation barriers are higher for reactions involving hydrogen-donating organocatalysts and kinetic experiments suggest that the catalysts bind stronger to the starting silyl ketene acetals than to transition structures thus leading to inefficient rearrangement reactions.

Synthèse totale des acides (+) et (–) nonactique à partir de carbohydrates

1981 ◽  
Vol 59 (3) ◽  
pp. 572-583 ◽  
Author(s):  
Robert E. Ireland ◽  
Jean-Paul Vevert
Keyword(s):  
Carbon Atom ◽  
Absolute Configuration ◽  
Claisen Rearrangement ◽  
Sigmatropic Rearrangement ◽  
Chiral Carbon ◽  
Ketene Acetal ◽  
Boat Form ◽  
Aliphatic Esters ◽  
Ketene Acetals

The synthesis of (−) and (+) nonactic acids (2a) and (2b) has been achieved starting from D-mannose (7) and D-gluono-γ-lactone (22) respectively. The key step in the synthesis is the [3,3]-sigmatropic rearrangement of the silylated ketene-acetals IV leading to control of the C-2 configuration of nonactic acid. The ketene-acetals were prepared from aliphatic esters of furanoid-glycals II, which were prepared in ten steps from the carbohydrate precursor. The chiral sites of the glycals arise from the corresponding centres in the starting monosaccharide. This type of ketene-acetal Claisen rearrangement leads to products containing the aldol portion required. At the same time knowledge of the absolute configuration of the chiral carbon atom of nonactic acid allows for the determination of the chair or boat form of the transition state of the [3,3]-sigmatropic rearrangement. [Journal translation]

scholarly journals Deracemizing α‐Branched Carboxylic Acids by Catalytic Asymmetric Protonation of Bis‐Silyl Ketene Acetals with Water or Methanol

2019 ◽  
Vol 58 (33) ◽  
pp. 11479-11482 ◽  
Author(s):  
Francesca Mandrelli ◽  
Aurélie Blond ◽  
Thomas James ◽  
Hyejin Kim ◽  
Benjamin List
Keyword(s):  
Carboxylic Acids ◽  
Ketene Acetals ◽  
Silyl Ketene Acetals ◽  
Catalytic Asymmetric

Perturbation theory of substituent effect. Importance of the field effect in transmission of the substituent effect

1980 ◽  
Vol 45 (6) ◽  
pp. 1655-1661 ◽  
Author(s):  
Robert Ponec
Keyword(s):  
Perturbation Theory ◽  
Carboxylic Acids ◽  
Quantum Chemical ◽  
Substituent Effect ◽  
Field Effect ◽  
Adequate Description ◽  
Meta Position ◽  
Unsaturated Carboxylic Acids

Various quantum chemical approaches to the problem of transmission of the substituent effect were compared. It was shown that inclusion of the electronic repulsion (field effect) was necessary to give a true picture of differences in ρ constants for reactions of the cis and trans isomers of substituted unsaturated carboxylic acids; the same holds for an adequate description of transmission of the substituent effect from the meta position on a given skeleton.

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