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DOI: 10.1055/sos-SD-026-00003

von Angerer, S.Science of Synthesis, (20052675.

A number of diverse cobalt complexes can be used as catalysts for the oxidation of secondary alcohols to ketones with molecular oxygen. The cobalt(II) or cobalt(III) compounds applied are of variable complexity.[‌244‌‌251‌] When cobalt(II) acetate or tris(acetylacetonato)cobalt(III) complex are used N-hydroxyphthalimide has to be added as a cooxidant to obtain aliphatic and alicyclic ketones in good yields (Table 5, entries 13).[‌244‌,‌245‌] With these reagents cyclic 1,3- and 1,4-diols are converted into the corresponding hydroxy ketones whereas cyclic 1,2-diols react to form mixtures of 1,2-diones and dicarboxylic acids. For the aerobic oxidation of alcohols, cobalt(II) Schiff base complexes, such as 90 and 91 (Scheme 57) can also be used as the catalyst either alone[‌252‌] or in the presence of aldehyde cofactors (entries 5 and 6).[‌247‌,‌248‌] Typical examples for the use of cobalt compounds, including bis(1,1,1-trifluoroacetylacetonato)cobalt(II) (92) (Table 5, entry 7), in the preparation of ketones 93 are listed in Table 5.

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