Mechanism of the Catalytic Oxidation of Tertiary Alcohols by the Water-Soluble Mn-TMPyP/KHSO5 System: β-Fragmentation versus O-Neophyl Rearrangement
✍ Scribed by Karine Wietzerbin; Jean Bernadou; Bernard Meunier
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 411 KB
- Volume
- 1999
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
Oxidation of 4-(1-hydroxy-1-phenylethyl)benzoic acid H 2 18 O under different reaction conditions show that the carbonyl oxygen atoms of AC and ABA originate either from HPEBA with a water-soluble metalloporphyrin as catalyst and KHSO 5 as oxygen atom donor gives the major products, substrate, water or dioxygen. However, the carbonyl oxygen atom in the ester group of BOBA originates from dioxygen acetophenone AC and acetylbenzoic acid ABA, by a C aliph -C Ar bond cleavage, but a minor product, benzoyloxybenzoic while the other oxygen atom of the ester remains unlabeled. These results can be explained by an O-neophyl acid BOBA, requires the insertion of an oxygen atom to form the ester. This compound becomes the main oxidation rearrangement of the initial alkoxyl radical to afford a carbon-based radical which then reacts with dioxygen or product on increasing the amount of acetonitrile in the reaction medium, and its formation is oxygen-dependent.
Mn IV -OH/water. In a competitive reaction pathway, direct βscission of the alkoxyl radical leads to unlabeled products. The conversion is drastically lowered by using D 2 O instead of H 2 O, suggesting that an alkoxyl radical is formed in the The oxidation of other tertiary diaryl alcohols is also discussed. rate-determining step. Labeling experiments using 18 O 2 or As part of our mechanistic studies on the biomimetic [a]