Selective multi-electron aggregation at a hypervalent iodine center by sequential disproportionation

Thai, Phong; Frey, Brandon L.; Figgins, Matthew T.; Thompson, Richard R.; Carmieli, Raanan; Powers, Dennis A.

doi:10.1039/d3cc00549f

Cited by 5 publications

(6 citation statements)

References 41 publications

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“…Recently, Powers and colleagues discovered that the disproportionation of electrochemically generated iodosylarenes can give the corresponding iodoxyarenes. [34] The selectivity for the iodine(V) : iodine(III) products was 4.2:1.0 under the optimal conditions. Other hypervalent iodine reagents in oxidation states above + 3 can also be obtained via electrochemical methods, particularly periodate.…”

Section: Iodine(v) Reagentsmentioning

confidence: 91%

“…Miyake and co‐workers also investigated the electrochemical production of iodine(V) reagents in aqueous conditions, [33] although mixtures of iodine(III) and iodine(V) products were obtained. Recently, Powers and colleagues discovered that the disproportionation of electrochemically generated iodosylarenes can give the corresponding iodoxyarenes [34] . The selectivity for the iodine(V) : iodine(III) products was 4.2:1.0 under the optimal conditions.…”

Section: Iodine(v) Reagentsmentioning

confidence: 99%

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Hypervalent Halogen Compounds in Electrochemical Reactions: Advantages and Prospects

2023

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The clean and facile electrochemical synthesis of hypervalent iodine reagents is a fast growing field. In the past 5 years, a diverse number of reaction types have been established, from fluorinations, oxidative cyclizations, C−N and C−H couplings and oxidations. Electrochemistry is beneficial in terms of sustainability as the requirement for chemical oxidants is eliminated. This contributes to cleaner processes with limited by‐product waste. Often, the purification of iodine(III) compounds is simple, since electrolysis is performed in the absence stoichiometric oxidants. Significant breakthroughs have been made recently, including the first asymmetric application, electrocatalytic applications, and even the synthesis of bromine(III) reagents using similar methodologies.magnified image

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Section: Iodine(v) Reagentsmentioning

confidence: 91%

Section: Iodine(v) Reagentsmentioning

confidence: 99%

Hypervalent Halogen Compounds in Electrochemical Reactions: Advantages and Prospects

2023

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“…We first carried out the stoichiometric reaction by mixing 1 and the commercially available oxidant 1-trifluoromethyl-1,2-benziodoxol-3(1H)one (acid CF 3 -Togni reagent), resulting in a purple solution after 2 min at room temperature. The ESI-HRMS ([M] + = 614.8710) analysis 28,45 of the reaction mixture and other evidence (vide infra) suggested the formation of a high-valent Ni IV complex 2 (Scheme 2) with both the benzoate part of the Togni reagent and the fluoroalkyl attached.…”

Section: Development Of the Catalyticmentioning

confidence: 97%

General High-Valent Nickel Metallocycle Catalyst for the Perfluoroalkylation of Heteroarenes and Peptides

Deolka,

Govindarajan,

Gridneva

et al. 2023

ACS Catal.

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“…2 During electrosynthetic studies of I(III) compounds featuring ortho-Lewis basic substituents, which Protasiewicz introduced to enhance the solubility of iodosyl-and iodoxybenzenes, 70 we had the opportunity to experimentally validate I(II) disproportionation as an elementary step characteristic of I(II) compounds (Figure 9). 71 Chemical oxidation of 2m by PIFA and BF 3 •OEt 2 in hfip, conditions previously developed to prepare iodanyl radicals, 4 resulted in the immediate formation of a dark blue solution with λ max = 647 nm (Figure 9a). The observed spectral features were well-reproduced by TD-DFT calculations of iodanyl radical 16c (Figure 9b).…”

Section: Disproportionation Of Iodanyl Radicalsmentioning

confidence: 98%

“…During exploratory electrosynthetic studies based on the disproportionation of anodically generated iodanyl radical 16c , we identified solvent-dependent reaction outcomes, with 21·H + being generated in MeCN and 21 being generated in TFE (Figure b) . Consistent with the Koser hypothesis for iodosylbenzene disproportionation, the combination of these two protonation states under ambient conditions results in rapid disproportionation to I(I) and I(V).…”

Section: Sustainable Iodoxybenzene Chemistrymentioning

confidence: 99%

Iodanyl Radical Catalysis

2023

Self Cite

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Conspectus Hypervalent iodine reagents find application as selective chemical oxidants in a diverse array of oxidative transformations. The utility of these reagents is often ascribed to (1) the proclivity to engage being selective two-electron redox transformations; (2) facile ligand exchange at the three-centered, four-electron (3c–4e) hypervalent iodine–ligand (I–X) bonds; and (3) the hypernucleofugacity of aryl iodides. One-electron redox and iodine radical chemistry is well-precedented in the context of inorganic hypervalent iodine chemistryfor example, in the iodide–triiodide couple that drives dye-sensitized solar cells. In contrast, organic hypervalent iodine chemistry has historically been dominated by the two-electron I(I)/I(III) and I(III)/I(V) redox couples, which results from intrinsic instability of the intervening odd-electron species. Transient iodanyl radicals (i.e., formally I(II) species), generated by reductive activation of hypervalent I–X bonds, have recently gained attention as potential intermediates in hypervalent iodine chemistry. Importantly, these open-shell intermediates are typically generated by activation of stoichiometric hypervalent iodine reagents, and the role of the iodanyl radical in substrate functionalization and catalysis is largely unknown. Our group has been interested in advancing the chemistry of iodanyl radicals as intermediates in the sustainable synthesis of hypervalent I(III) and I(V) compounds and as novel platforms for substrate activation at open-shell main-group intermediates. In 2018, we disclosed the first example of aerobic hypervalent iodine catalysis by intercepting reactive intermediates in aldehyde autoxidation chemistry. While we initially hypothesized that the observed oxidation was accomplished by aerobically generated peracids via a two-electron I(I)-to-I(III) oxidation reaction, detailed mechanistic studies revealed the critical role of acetate-stabilized iodanyl radical intermediates. We subsequently leveraged these mechanistic insights to develop hypervalent iodine electrocatalysis. Our studies resulted in the identification of new catalyst design principles that give rise to highly efficient organoiodide electrocatalysts that operate at modest applied potentials. These advances addressed classical challenges in hypervalent iodine electrocatalysis related to the need for high applied potentials and high catalyst loadings. In some cases, we were able to isolate the anodically generated iodanyl radical intermediates, which allowed direct interrogation of the elementary chemical reactions characteristic of iodanyl radicals. Both substrate activation via bidirectional proton-coupled electron transfer (PCET) reactions at I(II) intermediates and disproportionation reactions of I(II) species to generate I(III) compounds have been experimentally validated. This Account discusses the emerging synthetic and catalytic chemistry of iodanyl radicals. Results from our group have demonstrated that these open-shell species can play a critical role in...

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Selective multi-electron aggregation at a hypervalent iodine center by sequential disproportionation

Abstract: We demonstrate that sequential disproportionation reactions can enable selective aggregation of two- or four electron-holes at a hypervalent iodine center. Disproportionation of an anodically generated iodanyl radical affords an iodosylbenzene...

Cited by 5 publications

References 41 publications

Hypervalent Halogen Compounds in Electrochemical Reactions: Advantages and Prospects

Hypervalent Halogen Compounds in Electrochemical Reactions: Advantages and Prospects

General High-Valent Nickel Metallocycle Catalyst for the Perfluoroalkylation of Heteroarenes and Peptides

Iodanyl Radical Catalysis

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