Dataset Information

Cis-dihydroxylation of unsaturated potassium alkyl- and aryltrifluoroborates.

ABSTRACT: [reaction: see text] The cis-dihydroxylation of olefin-containing potassium alkyl- and aryltrifluoroborates proceeds readily in moderate to excellent yields. The resulting diols are efficient coupling partners in Suzuki-Miyaura-type reactions with both alkenyl and aryl bromides.

SUBMITTER: Molander GA

PROVIDER: S-EPMC2504008 | biostudies-literature | 2006 Jan

REPOSITORIES: biostudies-literature

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cis-dihydroxylation of unsaturated potassium alkyl- and aryltrifluoroborates.

Molander Gary A GA Figueroa Ruth R

Organic letters 20060101 1

[reaction: see text] The cis-dihydroxylation of olefin-containing potassium alkyl- and aryltrifluoroborates proceeds readily in moderate to excellent yields. The resulting diols are efficient coupling partners in Suzuki-Miyaura-type reactions with both alkenyl and aryl bromides. ...[more]

PMID: 16381571

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Project description:Rieske dioxygenases catalyze the reductive activation of O2 for the formation of cis-dihydrodiols from unactivated aromatic compounds. It is known that O2 is activated at a mononuclear non-heme iron site utilizing electrons supplied by a nearby Rieske iron sulfur cluster. However, it is controversial whether the reactive species is an Fe(III)-(hydro)peroxo or an Fe(II)-(hydro)peroxo (or electronically equivalent species formed by breaking the O-O bond). Here it is shown that benzoate 1,2 dioxygenase oxygenase component (BZDO) prepared in a form with the Rieske cluster oxidized and the mononuclear iron in the Fe(III) state can utilize H2O2 as a source of reduced oxygen to form the correct cis-dihydrodiol product from benzoate. The reaction approaches stoichiometric yield relative to the mononuclear Fe(III) concentration, being limited to a single turnover by inefficient product release from the Fe(III)-product complex. EPR and Mössbauer studies show that the iron remains ferric throughout this single turnover "peroxide shunt" reaction. These results strongly support Fe(III)-(hydro)peroxo (or Fe(V)-oxo-hydroxo) as the reactive species because there is no source of additional reducing equivalents to form the Fe(II)-(hydro)peroxo state. This conclusion could be further tested in the case of BZDO because the peroxide shunt occurs very slowly compared with normal turnover, allowing the reactive intermediate to be trapped for spectroscopic analysis. We attribute the slow reaction rate to a forced change in the normally strict order of the substrate binding and enzyme reduction steps that regulate the catalytic cycle. The reactive intermediate is a high-spin ferric species exhibiting an unusual negative zero field splitting and other EPR and Mössbauer spectroscopic properties reminiscent of previously characterized side-on-bound peroxide adducts of Fe(III) model complexes. If the species in BZDO is a similar adduct, its isomer shift is most consistent with an Fe(III)-hydroperoxo reactive state.

Dataset Information

Cis-dihydroxylation of unsaturated potassium alkyl- and aryltrifluoroborates.

Publications

cis-dihydroxylation of unsaturated potassium alkyl- and aryltrifluoroborates.

Similar Datasets

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