A theoretical study of reactivity and regioselectivity in the hydroxylation of adamantane by ferrate(VI)

Yoshihito Shiota, Naoki Kihara, Takashi Kamachi, Kazunari Yoshizawa

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26 Citations (Scopus)

Abstract

The conversion of adamantane to adamantanols mediated by ferrate (FeO42-), monoprotonated ferrate (HFeO4-), and diprotonated ferrate (H2FeO4) is discussed with the hybrid B3LYP density functional theory (DFT) method. Diprotonated ferrate is the best mediator for the activation of the C-H bonds of adamantane via two reaction pathways, in which 1-adamantanol is formed by the abstraction of a tertiary hydrogen atom (3°) and 2-adamantanol by the abstraction of a secondary hydrogen atom (2°). Each reaction pathway is initiated by a C-H bond cleavage via an H-atom abstraction that leads to a radical intermediate, followed by a C-O bond formation via an oxygen rebound step to lead to an adamantanol complex. The activation energies for the C-H cleavage step are 6.9 kcal/mol in the 1-adamantanol pathway and 8.4 kcal/mol in the 2-adamantanol pathway, respectively, at the B3LYP/6-311++G** level of theory, whereas those of the second reaction step corresponding to the rebound step are relatively small. Thus, the rate-determining step in the two pathways is the C-H bond dissociation step, which is relevant to the regioselectivity for adamantane hydroxylation. The relative rate constant (3°)/(2°) for the competing H-atom abstraction reactions is calculated to be 9.30 at 75 °C, which is fully consistent with an experimental value of 10.1.

Original languageEnglish
Pages (from-to)3958-3965
Number of pages8
JournalJournal of Organic Chemistry
Volume68
Issue number10
DOIs
Publication statusPublished - May 16 2003

All Science Journal Classification (ASJC) codes

  • Organic Chemistry

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