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Electron‐transfer‐catalyzed reactions, 7 . Aminium salt‐initiated oxygenation of ketenes — formation of succinic anhydrides
Author(s) -
Schmittel Michael,
von Seggern Heinke
Publication year - 1995
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.1995199510254
Subject(s) - chemistry , ketene , cycloaddition , succinic anhydride , salt (chemistry) , catalysis , photochemistry , oxygen , radical , regioselectivity , organic chemistry
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.