Building a Better Wacker

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Science  16 Dec 2005:
Vol. 310, Issue 5755, pp. 1743
DOI: 10.1126/science.310.5755.1743b

The Wacker oxidation is a well-established method for the conversion of olefins to aldehydes and ketones. The reaction involves activation of the olefin toward water addition by a palladium catalyst, followed by regeneration of the catalyst by oxygen. In general, however, the regeneration step cannot be accomplished directly, but instead requires a copper or quinone derivative to shuttle electrons between Pd and O2.

Mitsudome et al. show that a judicious choice of solvent eliminates the need for the co-catalyst. Using PdCl2 in dimethylacetamide (DMA) solvent, they achieve efficient conversion of long-chain (up to C20) terminal olefins to the corresponding 2-ketones on treatment with water under O2 pressure. The catalyst tolerates hydroxyl and cyano groups and can be recycled several times after heptane extraction. Electrochemical studies suggest that DMA lowers the oxidation potential of the catalyst in its Pd(0) state, thereby promoting direct oxidation by O2. — JSY

Angew. Chem. Int. Ed. 10.1002/anie.200502886 (2005).

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