Mild and Rapid Hydroxylation of Aryl/Heteroaryl Boronic Acids and Boronate Esters with <i>N</i>-Oxides

Zhu, Chen; Wang, Rui; Falck, John R.

doi:10.1021/ol301463c

Cited by 170 publications

(106 citation statements)

References 21 publications

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“…[18] The transformation was mild, rapid, and had broad functional group tolerance. As shown in Scheme 6, regardless of the electronic or steric character of the substrate, all arylboronic acids afforded phenols in excellent chemical yields.…”

Section: Carbon-oxygen Bond Formationmentioning

confidence: 99%

Transition Metal‐Free ipso‐Functionalization of Arylboronic Acids and Derivatives

Zhu

Falck

2014

Adv Synth Catal

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Arylboronic acids and their derivatives have been widely exploited as important synthetic precursors in organic synthesis, materials science, and pharmaceutical development. In addition to numerous applications in transition-metal-mediated cross-coupling reactions, transition-metal-free transformations involving arylboronic acids and derivatives have recently received a surge of attention for converting the C-B bond to C-C, C-N, C-O, and many other C-X bonds. Consequently, a wide range of useful compounds, e.g., phenols, anilines, nitroarenes, and haloarenes, have been readily synthesized. Amongst these efforts, many versatile reagents have been developed and a lot of practical approaches demonstrated. The research in this promising field is summarized in the current review and organized on the basis of the type of bonds being formed.

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Section: Carbon-oxygen Bond Formationmentioning

confidence: 99%

Transition Metal‐Free ipso‐Functionalization of Arylboronic Acids and Derivatives

Zhu

Falck

2014

Adv Synth Catal

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“…Focusing first on the former, the reaction could indeed be accelerated by turning to N , N -dialkylaryl N -oxides, which produce superior leaving groups compared to trialkylamines. [21] Kinetic parameters for this reaction were measured by employing a fluorogenic N , N -dialkylaryl N -oxide 6 , [22] obtained through m CPBA-mediated oxidation of the parent rhodol fluorophore. [23] The reaction of N -oxide 6 with phenylboronic acid in phosphate-buffered saline (PBS, pH 7.4) proceeded with a second-order rate constant of 1.28 ± 0.11 × 10 −3 M −1 s −1 (Fig.…”

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confidence: 99%

A Bioorthogonal Reaction of N‐Oxide and Boron Reagents

Kim

Bertozzi

2015

Angew Chem Int Ed

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Bioorthogonal reaction development has classically focused on bond-forming ligation reactions. In this report, we seek to expand the functional repertoire of such chemistries by introducing a new bond-cleaving reaction between N-oxide and boron reagents. The reaction features a large dynamic range of reactivity, showcasing second-order rate constants as high as 2.3 × 103 M−1s−1 using diboron reaction partners. Diboron displays minimal cell toxicity at millimolar concentrations, penetrates cell membranes, and effectively reduces N-oxides inside mammalian cells. This new bioorthogonal tool comprising miniscule components is well-suited for activating molecules within cells under chemical control. Additionally, we demonstrate that the metabolic diversity of nature enables the use of naturally occurring functionalities that display inherent biocompatibility alongside abiotic components for organism-specific applications.

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“…Our recent studies 10 on the hydroxylation of arylboronic acids by N -tertiary amine oxides prompted us to investigate if a similar strategy, via a leaving group-initiated 1,2-aryl migration, 11 would also work for the preparation of primary arylamines (Scheme 1). However, it was clear that achieving the metal-free amination would be significantly more challenging, since it is well-known that common electrophilic aminating agents (e.g., hydroxylamine- O -sulfonic acid and alkyl azides) do not affect boronic acids and their esters.…”

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confidence: 99%

Elusive Metal-Free Primary Amination of Arylboronic Acids: Synthetic Studies and Mechanism by Density Functional Theory

et al. 2012

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Herein, we disclose the first metal-free synthesis of primary aromatic amines from arylboronic acids, a reaction that has eluded synthetic chemists for decades. This remarkable transformation affords structurally diverse primary arylamines in good chemical yields, including a variety of halogenated primary anilines that often cannot be prepared via transition metal-catalyzed amination. The reaction is operationally simple, requires only a slight excess of aminating agent, proceeds under neutral or basic conditions and, importantly, it can be scaled up to provide multigram quantities of primary anilines. Density functional calculations reveal that the most likely mechanism involves a facile 1,2-aryl migration and that the presence of an ortho nitro group in the aminating agent plays a critical role in lowering the free energy barrier of the 1,2-aryl migration step.

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Mild and Rapid Hydroxylation of Aryl/Heteroaryl Boronic Acids and Boronate Esters with N-Oxides

Abstract: Aryl and heteroaryl boronic acids and boronate esters are rapidly, often within minutes, transformed into the corresponding phenols by N-oxides in an open flask at ambient temperature. This transformation has broad compatibility with a variety of functional groups.

Cited by 170 publications

References 21 publications

Transition Metal‐Free ipso‐Functionalization of Arylboronic Acids and Derivatives

Transition Metal‐Free ipso‐Functionalization of Arylboronic Acids and Derivatives

A Bioorthogonal Reaction of N‐Oxide and Boron Reagents

Elusive Metal-Free Primary Amination of Arylboronic Acids: Synthetic Studies and Mechanism by Density Functional Theory

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