Adding O to Olefins

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Science  22 Oct 2004:
Vol. 306, Issue 5696, pp. 579
DOI: 10.1126/science.306.5696.579b

Allylic oxidation, in which O is added to a carbon adjacent to a C-C double bond, is a key step in accessing a wide variety of useful organic compounds. Catino et al. have shown that a Rh dimer bound by four caprolactam ligands can catalyze this reaction at loadings as low as 0.1% relative to the carbon substrate. Using t-butyl hydroperoxide as the oxygen source, the authors convert 12 different cyclic olefins to enones. The reactions are complete within 1 hour and selectively form allylic C-O double bonds in the presence of alkyl, phenyl, carbonyl, and nitro groups. It seems that the crucial feature of the catalyst is a low one-electron oxidation potential, which leads to a mixed-valence Rh(II)-Rh(III) intermediate that the authors confirmed spectroscopically. This system improves on alternative methods that require stoichiometric metal oxidants or high catalyst loadings. — JSY

J. Am. Chem. Soc. 10.1021/ja045330o (2004).

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