Electron-transfer-catalyzed reactions, 7. Aminium salt-initiated oxygenation of ketenes — formation of succinic anhydrides
✍ Scribed by Schmittel, Michael ;von Seggern, Heinke
- Publisher
- John Wiley and Sons
- Year
- 1995
- Tongue
- English
- Weight
- 787 KB
- Volume
- 1995
- Category
- Article
- ISSN
- 0947-3440
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✦ Synopsis
Abstract
The aminium salt‐initiated oxygenation of ketenes 1a and 1b with molecular oxygen afforded in an unprecedented reaction mode the succinic anhydrides 2 and 3 within a few minutes at 0°C. From mechanistic investigations it is inferred, that the regioselective 1,3‐dipolar cycloaddition of an intermediate α‐lactone, independently trapped by cycloaddition to hexafluoroacetone, to the ketene constitutes the final step of the reaction sequence. Surprisingly, the oxygenation reaction occurred even when the reaction was carried out with rigorous exclusion of atmospheric oxygen. Evidence is presented that aminium salts are capable of both storing and activating molecular oxygen with remarkable efficiency, and that the reaction does not proceed via free ketene cation radicals.