Hypervalent‐Iodine(III) Mediated Tandem Oxidative Dearomatization/Aziridination Reaction of Phenolic Amines: Synthesis of Functionalized Unactivated Aziridines

2021 ◽  
Author(s):  
Chun-An Fan ◽  
Ye-Xing Cao ◽  
Patamawadee Silalai ◽  
Chun-Fang Liu ◽  
Ke-Yin Yu ◽  
...  
Keyword(s):  
Hypervalent Iodine ◽  
Oxidative Dearomatization

Oxidase Catalysis via Aerobically Generated Hypervalent Iodine Intermediates

2017 ◽  
Author(s):  
Asim Maity ◽  
Sung-Min Hyun ◽  
David Powers
Keyword(s):  
Ground State ◽  
Aerobic Oxidation ◽  
Reactive Intermediates ◽  
Substrate Oxidation ◽  
Hypervalent Iodine ◽  
Reaction Products ◽  
Oxidative Dearomatization ◽  
Triplet Ground State ◽  
Broad Array ◽  
Oxidation Chemistry

Development of sustainable oxidation chemistry demands strategies to harness O<sub>2</sub> as a terminal oxidant. In particular, oxidase catalysis, in which O<sub>2</sub> serves as a chemical oxidant without necessitating oxygen incorporation into reaction products, would allow diverse substrate functionalization chemistry to be coupled to O<sub>2</sub> reduction. Direct O<sub>2</sub> utilization must overcome the intrinsic challenges imposed by the triplet ground state of O<sub>2</sub> and the disparate electron inventories of four-electron O<sub>2</sub> reduction and two-electron substrate oxidation. Here, we generate hypervalent iodine reagents, a broadly useful class of selective two-electron oxidants, from O<sub>2</sub>. Synthesis of these oxidants is achieved by intercepting reactive intermediates of aldehyde autoxidation. The use of aryl iodides as mediators of aerobic oxidation underpins an oxidase catalysis platform that couples a broad array of substrate oxidations to O<sub>2</sub> reduction, including olefin functionalization chemistry, carbonyl a-oxidation, oxidative dearomatization, and aerobic C–H amination chemistry.

scholarly journals Mechanism of Iodine(III)-Promoted Oxidative Dearomatizing Hydroxylation of Phenols: Evidence for Radical-Chain Pathway

2020 ◽  
Author(s):  
Karol Kraszewski ◽  
Ireneusz Tomczyk ◽  
Aneta Drabinska ◽  
Krzysztof Bienkowski ◽  
Renata Solarska ◽  
...  
Keyword(s):  
High Resolution Mass Spectrometry ◽  
Hypervalent Iodine ◽  
Synthetic Approach ◽  
Chain Mechanism ◽  
Mechanistic Studies ◽  
Radical Chain ◽  
Oxidative Dearomatization ◽  
Radical Chain Mechanism ◽  
Rate Determining Step ◽  
Mechanism Of The Reaction

In the recent years, the dearomatization of phenols with the addition of nucleophiles to the aromatic ring, induced by hypervalent iodine(III) reagents and catalysts, has emerged as a highly useful synthetic approach. However, experimental mechanistic studies of this important process have been extremely scarce. As a result, the mechanism of the reaction remained elusive and as of today there exist as many as three distinct mechanistic proposals. In this report, we describe systematic investigations of the dearomatizing hydroxylation of phenols using an array of experimental techniques. Kinetics, EPR spectroscopy, and reactions with radical probes demonstrate that all the previously suggested mechanisms are incorrect, and that the transformation in fact proceeds via a radical-chain mechanism, with the aryloxyl radical being the key chain-carrying intermediate. Moreover, UV and NMR spectroscopy, high-resolution mass spectrometry, and cyclic voltammetry show that before reacting with the aryloxyl radical, water molecule becomes activated by the interaction with the iodine(III) center, causing this formally nucleophilic substrate to act as an electrophile. The C–O bond formation is identified as the rate-determining step of the reaction. This step generates the dearomatized product and an iodanyl(II) species, which is the second chain-carrying radical. The radical-chain mechanism emerging from our investigations allows to rationalize all other existing observations regarding the iodine(III)-promoted oxidative dearomatization of phenols.<br>

scholarly journals Mechanism of Iodine(III)-Promoted Oxidative Dearomatizing Hydroxylation of Phenols: Evidence for Radical-Chain Pathway

2020 ◽  
Author(s):  
Karol Kraszewski ◽  
Ireneusz Tomczyk ◽  
Aneta Drabinska ◽  
Krzysztof Bienkowski ◽  
Renata Solarska ◽  
...  
Keyword(s):  
High Resolution Mass Spectrometry ◽  
Hypervalent Iodine ◽  
Synthetic Approach ◽  
Chain Mechanism ◽  
Mechanistic Studies ◽  
Radical Chain ◽  
Oxidative Dearomatization ◽  
Radical Chain Mechanism ◽  
Rate Determining Step ◽  
Mechanism Of The Reaction

In the recent years, the dearomatization of phenols with the addition of nucleophiles to the aromatic ring, induced by hypervalent iodine(III) reagents and catalysts, has emerged as a highly useful synthetic approach. However, experimental mechanistic studies of this important process have been extremely scarce. As a result, the mechanism of the reaction remained elusive and as of today there exist as many as three distinct mechanistic proposals. In this report, we describe systematic investigations of the dearomatizing hydroxylation of phenols using an array of experimental techniques. Kinetics, EPR spectroscopy, and reactions with radical probes demonstrate that all the previously suggested mechanisms are incorrect, and that the transformation in fact proceeds via a radical-chain mechanism, with the aryloxyl radical being the key chain-carrying intermediate. Moreover, UV and NMR spectroscopy, high-resolution mass spectrometry, and cyclic voltammetry show that before reacting with the aryloxyl radical, water molecule becomes activated by the interaction with the iodine(III) center, causing this formally nucleophilic substrate to act as an electrophile. The C–O bond formation is identified as the rate-determining step of the reaction. This step generates the dearomatized product and an iodanyl(II) species, which is the second chain-carrying radical. The radical-chain mechanism emerging from our investigations allows to rationalize all other existing observations regarding the iodine(III)-promoted oxidative dearomatization of phenols.<br>

scholarly journals Recent Advances in the Selective Oxidative Dearomatization of Phenols to o-Quinones and o-Quinols with Hypervalent Iodine Reagents

Synlett ◽  
2021 ◽  
Author(s):  
Sarah E. Wengryniuk ◽  
Xiao Xiao
Keyword(s):  
Coordination Chemistry ◽  
Organic Synthesis ◽  
Phenol Oxidation ◽  
Hypervalent Iodine ◽  
Direct Oxidation ◽  
Oxidative Dearomatization ◽  
Total Syntheses ◽  
Recent Advances

Abstract ortho-Quinones are valuable molecular frameworks with diverse applications across biology, materials, organic synthesis, catalysis, and coordination chemistry. Despite their broad utility, their synthesis remains challenging, in particular via the direct oxidation of readily accessible phenols, due to the need to affect regioselective ortho oxidation coupled with the sensitivity of the resulting o-quinone products. The perspective looks at the emergence of I(V) hypervalent iodine reagents as an effective class of oxidants for regioselective o-quinone synthesis. The application of these reagents in regioselective phenol oxidation to both o-quinones and o-quinols will be discussed, including a recent report from our laboratory on the first method for the oxidation of electron-deficient phenols using a novel nitrogen-ligated I(V) reagent. Also included are select examples of total syntheses utilizing this methodology as well as recent advancements in chiral I(V) reagent design for asymmetric phenol dearomatization.1 Introduction2 I(V): Hypervalent Iodine Reagents3 I(V)-Mediated Dearomatization to o-Quinones4 Bisnitrogen-Ligated I(V) Reagents: ortho Dearomatization of Electron-Poor Phenols5 I(V)-Mediated Dearomatization to o-Quinols6 Conclusion and Outlook

Oxidase Catalysis via Aerobically Generated Hypervalent Iodine Intermediates

2017 ◽  
Author(s):  
Asim Maity ◽  
Sung-Min Hyun ◽  
David Powers
Keyword(s):  
Ground State ◽  
Aerobic Oxidation ◽  
Reactive Intermediates ◽  
Substrate Oxidation ◽  
Hypervalent Iodine ◽  
Reaction Products ◽  
Oxidative Dearomatization ◽  
Triplet Ground State ◽  
Broad Array ◽  
Oxidation Chemistry

Development of sustainable oxidation chemistry demands strategies to harness O<sub>2</sub> as a terminal oxidant. In particular, oxidase catalysis, in which O<sub>2</sub> serves as a chemical oxidant without necessitating oxygen incorporation into reaction products, would allow diverse substrate functionalization chemistry to be coupled to O<sub>2</sub> reduction. Direct O<sub>2</sub> utilization must overcome the intrinsic challenges imposed by the triplet ground state of O<sub>2</sub> and the disparate electron inventories of four-electron O<sub>2</sub> reduction and two-electron substrate oxidation. Here, we generate hypervalent iodine reagents, a broadly useful class of selective two-electron oxidants, from O<sub>2</sub>. Synthesis of these oxidants is achieved by intercepting reactive intermediates of aldehyde autoxidation. The use of aryl iodides as mediators of aerobic oxidation underpins an oxidase catalysis platform that couples a broad array of substrate oxidations to O<sub>2</sub> reduction, including olefin functionalization chemistry, carbonyl a-oxidation, oxidative dearomatization, and aerobic C–H amination chemistry.

Oxidase Catalysis via an Aerobically Generated Dess-Martin Periodinane Analogue

2018 ◽  
Author(s):  
Asim Maity ◽  
Sung-Min Hyun ◽  
Alan Wortman ◽  
David Powers
Keyword(s):  
Chemical Synthesis ◽  
Aerobic Oxidation ◽  
Substrate Oxidation ◽  
Oxidation Catalysis ◽  
Hypervalent Iodine ◽  
Oxidation Reactions ◽  
Broad Array ◽  
Oxidation Chemistry ◽  
Reactive Oxidants

<p>Hypervalent iodine(V) reagents, such as Dess-Martin periodinane (DMP) and 2-iodoxybenzoic acid (IBX), are broadly useful oxidants in chemical synthesis. Development of strategies to access these reagents from O2 would immediately enable use of O2 as a terminal oxidant in a broad array of substrate oxidation reactions. Recently we disclosed the aerobic synthesis of I(III) reagents by intercepting reactive oxidants generated during aldehyde autoxidation. Here, we couple aerobic oxidation of iodobenzenes with disproportionation of the initially generated I(III) compounds to generate I(V) reagents. The aerobically generated I(V) reagents exhibit substrate oxidation chemistry analogous to that of DMP. Further, the developed aerobic generation of I(V) has enabled the first application of I(V) intermediates in aerobic oxidation catalysis.</p>

Regioselective C3-H Trifluoromethylation of 2H-Indazole Under Transition-Metal-Free Photoredox Catalysis

2019 ◽  
Author(s):  
Arumugavel Murugan ◽  
Venkata Nagarjuna Babu ◽  
Nagaraj Sabarinathan ◽  
Sharada Duddu. S
Keyword(s):  
Transition Metal ◽  
Visible Light ◽  
Practical Approach ◽  
Hypervalent Iodine ◽  
Radical Mechanism ◽  
Photoredox Catalysis ◽  
Metal Free

Here we report a visible-light-promoted metal-free regioselective C3-H trifluoromehtylation reaction that proceeds via radical mechanism and which supported by control experiments. The combination of photoredox catalysis and hypervalent iodine reagent provides a practical approach for the present trifluoromethylation reaction and synthesis of a library of trifluoromethylated indazoles.

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