Clean Coupling

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Science  16 Jan 2009:
Vol. 323, Issue 5912, pp. 311
DOI: 10.1126/science.323.5912.311c

Alcohol oxidation is a crucial step in the preparation of many drugs and fine chemicals, but it often requires large amounts of toxic reagents. Zweifel et al. present a rhodium catalyst that can dehydrogenatively couple a range of alcohols with water, methanol, or various amines (including ammonia, a generally recalcitrant substrate) to afford the corresponding acid, ester, or amide directly. The reactions proceed in a few hours at room temperature, driven by transfer of the liberated hydrogen to a cyclohexanone acceptor that can subsequently be recycled by reaction with hydrogen peroxide. Primary alcohols are oxidized selectively, and the catalyst tolerates olefin, thioether, and pyridine substituents. Simulations support a mechanism involving the transfer of a hydride to the Rh center, with accompanying protonation of a coordinated nitrogen ligand. — JSY

Angew. Chem. Int. Ed. 48, 559 (2009).

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