Umlagerung und Spaltung von α, β‐Dioxopropionsäureestern in alkalischem Milieu. 28. Mitt. über Reduktone und Tricarbonylverbindungen [1]

Rodé‐Gowal, Heike; Dao, Huu Le Dao Huu Le; Dahn, H.

doi:10.1002/hlca.19740570737

Cited by 13 publications

(3 citation statements)

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“…In agreement with earlier work on triketones (ref 3), labeling experiments by Dahn et al 142 showed that the migrating group in the benzilic acid rearrangement of an R,β-diketoester is the carboalkoxy group.…”

Section: Rearrangement Reactionssupporting

confidence: 91%

The Chemistry of Vicinal Polycarbonyl Compounds

2000

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Section: Rearrangement Reactionssupporting

confidence: 91%

The Chemistry of Vicinal Polycarbonyl Compounds

2000

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“…spectra: in CDC13 lb" shows in the I3C-NMR. two (labelled) carbonyl signals for C (2) indicating an equilibrium mixture of unhydrated and hydrated lb, and correspondingly in the H-NMR. two sets of ethyl protons, but only one I3C (2) and one set of ethyl-H signals in D20-solution.…”

Section: -0-mentioning

confidence: 99%

“…two (labelled) carbonyl signals for C (2) indicating an equilibrium mixture of unhydrated and hydrated lb, and correspondingly in the H-NMR. two sets of ethyl protons, but only one I3C (2) and one set of ethyl-H signals in D20-solution. In the MS. of the mixture the appearance of fragments m/z 97 (C3H5-CO-CO) and 1 15 (C3HS-CO-C (OH),) supports hydration.…”

Section: -0-mentioning

confidence: 99%

Alkoxycarbonyl‐ and Carboxylate‐Group Migrations in the Benzilic Acid Rearrangement of Ethyl Cyclopropane‐2, 3‐dioxopropionate

Dahn

Dao

Hunma

1982

Helvetica Chimica Acta

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SummaryIn alkaline medium C3H5-CO-C (OH),-COOEt (lb) is transformed into C3H5-C (OH)(COOH), (2a). Labelling experiments show that the cyclopropyl group is not shifted, but only ROOC and/or -0,C groups. GC./MS. and NMR. analysis after incomplete reaction show that both ROOC-and -02C-groups migrate; at higher pH (ca. 14) the ester group rearrangement seems to be more important than at pH ca. 9-10. a, 8-Dioxocarboxylic esters form rather stable hydrates in the presence of water; these can be attacked by sufficiently basic nucleophiles, e.g. OH-, at three different positions (Scheme): A: at C(1), leading to hydrolysis of the ester group; B: at C(2), leading to hydrate-anions which undergo a benzilic acid type rearrangement via migration of a ROOC or -0,C group; C: at C(3), forming a bishydrate-anion which can be cleaved in a retro-aldol-type reaction. Path C prevails if the substituent R at C(3) is electron-attracting, e.g. aryl of CF3, favouring the hydration of the P-carbonyl group, whereas paths A and B are used when the hydration of the B-carbonyl group is diminished by electron donation (R= alkyl) or by steric effects (R= mesityl) [2]. The balance between paths A and B depends upon pH: at high pH (ca. 14) the hydrate at C (2) is transformed into its anion triggering the migration of COOR' (B), whereas at pH ca. 10 the ester group is hydrolysed first, followed by migration of the -0OC group [3].The cyclopropyl group is considerably electron.-releasing without important steric constraint, but is at the same time a good migrating group in the benzilic acid rearrangement [4]; so we were interested to see how it influences the balance between reaction paths A, B and C.

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Selenium Dioxide Oxidation

Rabjohn

2011

Organic Reactions

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Selenium dioxide has developed considerable stature since it was first reviewed in this series. Search for examples of oxidation by selenium dioxide or selenious acid is difficult because the terms are seldom indexed. Frequently it is difficult to decide whether selenium dioxide or selenious acid was the oxidizing agent employed in a reaction because it is impossible to determine if water was present. The determination is complex because the free acid or anhydride may react reversibly or irreversibly with various solvents such as alcohols or acids. To give selenium‐containing compounds of unknown structure which might be the real oxidizing gents. In this chapter, the practical aspects of oxidation with selenium dioxide are summarized. Mechanisms are treated in detail.

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Umlagerung und Spaltung von α, β‐Dioxopropionsäureestern in alkalischem Milieu. 28. Mitt. über Reduktone und Tricarbonylverbindungen [1]

Cited by 13 publications

References 16 publications

The Chemistry of Vicinal Polycarbonyl Compounds

The Chemistry of Vicinal Polycarbonyl Compounds

Alkoxycarbonyl‐ and Carboxylate‐Group Migrations in the Benzilic Acid Rearrangement of Ethyl Cyclopropane‐2, 3‐dioxopropionate

Selenium Dioxide Oxidation

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