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DOI: 10.1055/sos-SD-001-00322

Malacria, M.; Aubert, C.; Renaud, J.-L.Science of Synthesis, (20011491.

The commercially available tris(acetylacetonato)cobalt(III) exhibits interesting properties as a precatalyst. Indeed, when it is reduced by diethylaluminum chloride in the presence of a bidentate phosphine such as 1,2-bis(diphenylphosphanyl)ethane or triphenylphosphine, the resulting catalytic system is very effective in promoting inter- and intramolecular homo-DielsAlder reactions[‌230‌] and the carbocyclizations of acyclic enedienes.[‌231‌] In these cases, the cobalt(III) precatalyst is presumably reduced by the diethylaluminum chloride to either cobalt(0) or cobalt(I) species, but very little is known about the structure of the catalytically active complex. In the presence of oxygen, and without any additive, it was shown that tris(acetylacetonato)cobalt(III) is able to catalyze the oxidation of vinyl aromatic compounds and also cyclic ethers;[‌232‌] however, the mechanism of such oxidations has not yet been elucidated. One example describing the efficiency of this catalyst in the epoxidation of norbornene has also been reported.[‌232‌]