Chapter 3. The Application of Nitroxides in Organic Synthesis

Verdhi, Lenin Kumar; Szpilman, Alex M.

doi:10.1039/9781788019651-00071

Cited by 4 publications

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“…While nitroxides are outstanding catalysts and reagents for chemical synthesis 12 and even have seen use in enantioselective oxidation of alcohols, 13 their use in atroposelective oxidative kinetic resolution (OKR) and desymmetrization is still in infancy with the work by Blandin being the first example. 14 As part of our longstanding interest in nitroxides, 9 , 15 we recently reported our preliminary findings 16 on chiral nitroxide-copper co-catalyzed aerobic OKR of axially chiral N -aryl-pyrroles ( Scheme 1 b) using readily available (prepared in only five steps) 16 chiral α-hydrogen pre-catalyst 1 (97% ee , see Scheme 2 for the structure).…”

Section: Introductionmentioning

confidence: 99%

Catalytic Atroposelective Aerobic Oxidation Approaches to Axially Chiral Molecules

et al. 2023

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A copper and chiral nitroxide co-catalyzed aerobic enantioselective oxidation process has been developed that allows access to axially chiral molecules. Two complementary atroposelective approaches, oxidative kinetic resolution (OKR) and desymmetrization, were studied using ambient air as the stoichiometric terminal oxidant. OKR of rac-N-arylpyrrole alcohols and rac-biaryl alcohols affords the optically pure compounds with er up to 3.5:96.5 and 5.5:94.5, respectively. Desymmetrization of prochiral diols provides axially chiral biaryl compounds with er up to 99:1.

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Section: Introductionmentioning

confidence: 99%

Catalytic Atroposelective Aerobic Oxidation Approaches to Axially Chiral Molecules

et al. 2023

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“…We previously reported on a novel design concept for the preparation of uniquely stable α-hydrogen-substituted nitroxides. , This concept allowed us to synthesize two new families of stable nitroxides possessing α-hydrogens, namely, 2,3-dihydro-isoazaphenalene (IAPNO) and isoindoline (IINO) nitroxides. In addition, the high catalytic efficiency of IAPNO nitroxides in the oxidation of alcohols as a one-electron oxidant in combination with a copper co-catalyst, acting as a second one-electron oxidant, , under aerobic conditions was reported …”

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confidence: 99%

Copper- and Chiral Nitroxide-Catalyzed Oxidative Kinetic Resolution of Axially Chiral N-Arylpyrroles

2022

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A readily prepared C2-symmetric, α-hydrogen-substituted chiral hydroxylamine serves as a precatalyst to generate a chiral nitroxide in situ. This chiral nitroxide catalyst in combination with a copper co-catalyst functions as an oxidant for an unprecedented enantioselective oxidative kinetic resolution (OKR) of racemic axially chiral N-arylpyrrole alcohols using atmospheric oxygen as an environmentally friendly terminal oxidant. The OKR process provides the axially chiral N-arylpyrroles in er up to 3.5:96.5 and with s factors up to 24.

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Ambipolar diarylnitroxides: Molecular design and electrochemical testing

Magdesieva

2022

Electrochemical Science Adv

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Possible approaches to molecular design of stable diarylnitroxyl radicals capable to form sufficiently stable cations and anions under one‐electron oxidation and reduction are discussed. Both covalent and noncovalent stabilizing “tools” are considered. The main focus is made on the dynamic stabilization of oppositely charged redox states of a molecule through conformational changes. The efficiency of the approaches was confirmed on a wide range of novel diarylnitroxides designed accordingly to the suggested guidelines. Spectral and quantum‐chemical data support fast conformational changes accompanying electron transfer steps and facilitating stabilization of the cationic and anionic species. Voltammetric study of new compounds revealed the formation of reversible redox couples in both anodic and cathodic areas for the majority of nitroxides making them suitable for practical application.

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Chapter 3. The Application of Nitroxides in Organic Synthesis

Cited by 4 publications

References 0 publications

Catalytic Atroposelective Aerobic Oxidation Approaches to Axially Chiral Molecules

Catalytic Atroposelective Aerobic Oxidation Approaches to Axially Chiral Molecules

Copper- and Chiral Nitroxide-Catalyzed Oxidative Kinetic Resolution of Axially Chiral N-Arylpyrroles

Ambipolar diarylnitroxides: Molecular design and electrochemical testing

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