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Oxidation of electron-deficient phenols mediated by hypervalent iodine(V) reagents: fundamental mechanistic features revealed by a density functional theory-based investigation

journal contribution
posted on 2023-05-21, 02:11 authored by Jalali, M, Alexander BissemberAlexander Bissember, Brian YatesBrian Yates, Wengryniuk, SE, Alireza AriafardAlireza Ariafard
Hypervalent iodine (HVI) compounds are efficient reagents for the double oxidative dearomatization of electron-rich phenols to o-quinones. We recently reported that an underexplored class of iodine(V) reagents possessing bidentate bipyridine ligands, termed Bi(N)-HVIs, could dearomatize electron-poor phenols for the first time. To understand the fundamental mechanistic basis of this unique reactivity, density functional theory (DFT) was utilized. In this way, different pathways were explored to determine why Bi(N)-HVIs are capable of facilitating these challenging transformations while more traditional hypervalent species, such as 2-iodoxybenzoic acid (IBX), cannot. Our calculations reveal that the first redox process is the rate-determining step, the barrier of which hinges on the identity of the ligands bound to the iodine(V) center. This crucial process is composed of three steps: (a) ligand exchange, (b) hypervalent twist, and (c) reductive elimination. We found that strong coordinating ligands disfavor these elementary steps, and, for this reason, HVIs bearing such ligands cannot oxidize the electron-poor phenols. In contrast, the weakly coordinating triflate ligands in Bi(N)-HVIs allow for the kinetically favorable oxidation. It was identified that trapping in situ-generated triflic acid is a key role played by the bidentate bipyridine ligands in Bi(N)-HVIs as this serves to minimize the decomposition of the ortho-quinone product.

Funding

Australian Research Council

University of Wollongong

History

Publication title

Journal of Organic Chemistry

Volume

86

Issue

17

Pagination

12237-12246

ISSN

0022-3263

Department/School

School of Natural Sciences

Publisher

Amer Chemical Soc

Place of publication

1155 16Th St, Nw, Washington, USA, Dc, 20036

Rights statement

© 2021 American Chemical Society

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the chemical sciences

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