Solvent- and additive-free oxidative amidation of aldehydes using a recyclable oxoammonium salt

Sandoval, Arturo León; Doherty, Katrina E.; Wadey, Geoffrey P.; Leadbeater, Nicholas E.

doi:10.1039/d2ob00307d

Cited by 14 publications

(12 citation statements)

References 80 publications

(11 reference statements)

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“…Scheme 16). 747 Mixed anhydrides can be prepared from aldehydes and carboxylic acids by oxidizing the hemiacetals formed from the two substrates. 748 The anhydride can be easily further transformed to the desired ester or (Weinreb) amide.…”

Section: Oxidations Of Aldehydes and Iminesmentioning

confidence: 99%

Organic Synthesis Using Nitroxides

Leifert

Studer

2023

Chem. Rev.

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Nitroxides, also known as nitroxyl radicals, are long-lived or stable radicals with the general structure R 1 R 2 N−O • . The spin distribution over the nitroxide N and O atoms contributes to the thermodynamic stability of these radicals. The presence of bulky N-substituents R 1 and R 2 prevents nitroxide radical dimerization, ensuring their kinetic stability. Despite their reactivity toward various transient C radicals, some nitroxides can be easily stored under air at room temperature. Furthermore, nitroxides can be oxidized to oxoammonium salts (R 1 R 2 N�O + ) or reduced to anions (R 1 R 2 N−O − ), enabling them to act as valuable oxidants or reductants depending on their oxidation state. Therefore, they exhibit interesting reactivity across all three oxidation states. Due to these fascinating properties, nitroxides find extensive applications in diverse fields such as biochemistry, medicinal chemistry, materials science, and organic synthesis. This review focuses on the versatile applications of nitroxides in organic synthesis. For their use in other important fields, we will refer to several review articles. The introductory part provides a brief overview of the history of nitroxide chemistry. Subsequently, the key methods for preparing nitroxides are discussed, followed by an examination of their structural diversity and physical properties. The main portion of this review is dedicated to oxidation reactions, wherein parent nitroxides or their corresponding oxoammonium salts serve as active species. It will be demonstrated that various functional groups (such as alcohols, amines, enolates, and alkanes among others) can be efficiently oxidized. These oxidations can be carried out using nitroxides as catalysts in combination with various stoichiometric terminal oxidants. By reducing nitroxides to their corresponding anions, they become effective reducing reagents with intriguing applications in organic synthesis. Nitroxides possess the ability to selectively react with transient radicals, making them useful for terminating radical cascade reactions by forming alkoxyamines. Depending on their structure, alkoxyamines exhibit weak C−O bonds, allowing for the thermal generation of C radicals through reversible C−O bond cleavage. Such thermally generated C radicals can participate in various radical transformations, as discussed toward the end of this review. Furthermore, the application of this strategy in natural product synthesis will be presented.

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Section: Oxidations Of Aldehydes and Iminesmentioning

confidence: 99%

Organic Synthesis Using Nitroxides

Leifert

Studer

2023

Chem. Rev.

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“…Further advances through oxidation with the nitrate Bobbitt's salt (82), which facilitates oxidative amination with pyrazole and similar heterocycles without any additional additives and in high yield. 72,73…”

Section: Oxidation Of Aldehydesmentioning

confidence: 99%

“…39 The substrate scope of this reaction is fairly large and works best when electron-donating substituents are present on the aryl ring and the corresponding alcohol partner Scheme 22 Oxidation of aldehydes and ketones both stoichiometrically with 1 and catalytically using 2 to access N-acyl pyrazoles. [70][71][72][73] Scheme 23 Oxidative cleavage of ethers by 1. 39,41,74,75 is highly hindered (e.g., 106a-c).…”

Section: Oxidative Cleavagementioning

confidence: 99%

Recent advancements in the use of Bobbitt's salt and 4-acetamidoTEMPO

Bray,

Stephens,

Weierbach

et al. 2023

Chem. Commun.

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“…6 When employing 4 , the nitrate anion analogue of 1 , it is possible to oxidize alcohols to the corresponding carbonyl compounds very effectively. 7 8 9 These transformations can be performed using 0.5–0.6 equiv of 4 and the substrate scope proves to be quite broad. The reactions can be performed in solvent with silica gel as an additive (Scheme 1a ) 9 or under solvent-free or mechanochemical conditions without the need for additives (Scheme 1b ).…”

Section: Table 1 Optimization Of Reaction Conditions ...mentioning

confidence: 99%

Oxidation of Alcohols to Aldehydes and Ketones Using a Catalytic Pairing of a Nitroxide and Nitric Acid

Leadbeater,

Sharma,

Sandoval

2023

SynOpen

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A methodology for the oxidation of alcohols to aldehydes and ketones is presented. The approach employs catalytic quantities of a nitroxide and nitric acid, with no additives or metal catalysts being required. It proves effective for a range of aromatic, heteroaromatic, and aliphatic alcohol substrates, the desired products being formed in good to excellent yield. In the case of primary alcohols, the oxidation can be stopped at the aldehyde without concomitant formation of the corresponding carboxylic acid.

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Solvent- and additive-free oxidative amidation of aldehydes using a recyclable oxoammonium salt

Abstract: A range of acyl azoles have been prepared from aromatic, heteroaromatic, and aliphatic aldehydes by means of an oxidative amidation reaction. The methodology employs a substoichiometric quantity of an oxoammonium...

Cited by 14 publications

References 80 publications

Organic Synthesis Using Nitroxides

Organic Synthesis Using Nitroxides

Recent advancements in the use of Bobbitt's salt and 4-acetamidoTEMPO

Oxidation of Alcohols to Aldehydes and Ketones Using a Catalytic Pairing of a Nitroxide and Nitric Acid

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