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Computational analysis of site differences in selective aliphatic C–H hydroxylation by nonheme iron–oxo complexes

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Abstract

Selective C–H hydroxylation by nonheme iron complexes offers a promising method in the field of organic synthesis. Aliphatic C–H bond oxidation reactions of pivalate (R) catalyzed by [Fe(S,S-PDP)(CH3CN)2]2+ (CAT1) were examined using the density functional theory. Our calculations of the CH3CN solvent agree with the experimental findings. However, it was observed that the gas-phase results did not replicate selective C–H hydroxylation observed experimentally when CAT1 catalyzed hydrocarbon oxidations by H2O2 via an HO–FeV[double bond, length as m-dash]O oxidant (CAT1a). We inferred that the difference was mainly from hydrogen bonding formation, (CAT1a) O–H⋯O[double bond, length as m-dash]C (R), in certain gaseous H-abstraction transition states (TSH). Then, the appearance of the stronger (CAT1a) O–H⋯N[triple bond, length as m-dash]CCH3-solvent weakened the aforementioned interaction, leading to C–H activation influenced primarily by their electronic and steric properties. Such a deduction explained the same selective C–H found in both phases of reactions with CAT1b, a cyclic ferric peracetate oxidant, by the reason of TSH without the influence of H-bonding. Another interesting finding was that the commonly recognized radical intermediate was further isomerized by a favorable electron rearrangement. Thus, the subsequent OH-rebound behavior proceeded by an electrostatic interaction. This study provides mechanistic clues for modifying regioselective C–H hydroxylation for molecule synthesis applications.

Graphical abstract: Computational analysis of site differences in selective aliphatic C–H hydroxylation by nonheme iron–oxo complexes

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Publication details

The article was received on 08 Mar 2017, accepted on 26 Apr 2017 and first published on 28 Apr 2017


Article type: Paper
DOI: 10.1039/C7CP01479A
Citation: Phys. Chem. Chem. Phys., 2017, Advance Article
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    Computational analysis of site differences in selective aliphatic C–H hydroxylation by nonheme iron–oxo complexes

    J. Wang, Y. Zhao and P. Lee, Phys. Chem. Chem. Phys., 2017, Advance Article , DOI: 10.1039/C7CP01479A

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