Nickel‐Catalyzed Tandem Ring Contraction of TEMPO and C−N Bond Transamination of Enaminones toward Amino Diversity of Enaminones

Wu, Huayue; Luo, Tao; Wan, Jie‐Ping; Jiang, Jian-Wen; Liu, Yunyun

doi:10.1002/ejoc.202200552

Cited by 10 publications

(2 citation statements)

References 60 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Lithiated phosphorus compounds react efficiently with TEMPO + or TEMPO through SET to the corresponding P radicals. The generated TEMPO (from TEMPO + ) or a second equivalent TEMPO (if TEMPO is used as the oxidant) subsequently traps the intermediate P radical to give a P -nitroxyl compound, which undergoes fast N–O bond cleavage. − In a recent publication, the reaction of the triphenyl phosphine radical cation with TEMPO to give the cationic TEMPO–P + Ph 3 adduct was suggested, which further reacts in a Stieglitz-type rearrangement to 2,2-dimethylpyrrolidine and phosphine oxide …”

Section: Oxidation Reactionsmentioning

confidence: 99%

Organic Synthesis Using Nitroxides

Leifert

Studer

2023

Chem. Rev.

View full text Add to dashboard Cite

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.

show abstract

Section: Oxidation Reactionsmentioning

confidence: 99%

Organic Synthesis Using Nitroxides

Leifert

Studer

2023

Chem. Rev.

View full text Add to dashboard Cite

show abstract

“…Generally, the enriched reactivity in enaminones comes from the HOMO heightening effect of the amino group in the alkenyl structure. Consequently, the majority of enaminone-based organic reactions proceed via a transformation on the enamine fragment such as the α-C–H bond, the π-bond in the alkene moiety, the whole alkenyl CC double bond, and the C–N bond, as well as the cascade annulation reactions by multiple transformations on these sites and the reactive carbonyl for the construction of both aromatic and nonaromatic cyclic products (Scheme A). In contrast to the well-developed synthetic reactions in the OCCCN unit, synthetic reactions making use of the transformation of the chemical bonds other than this unit are much less developed.…”

mentioning

confidence: 99%

Three-Component Fusion to Pyrazolo[5,1-a]isoquinolines via Rh-Catalyzed Multiple Order Transformation of Enaminones

et al. 2023

Self Cite

View full text Add to dashboard Cite

A facile and practical method for the synthesis of fused tricyclic pyrazolo[5,1-a]isoquinolines has been realized via the reactions of enaminones, hydrazine hydrochloride, and internal alkynes. By means of Rh catalysis, the extraordinary high-order bond functionalization, including the transformation of aryl C−H, ketone C�O, and alkenyl C−N bonds in the enaminones, marks the major feature of the cascade reactions. The results disclose the individual advantage of enaminones in the design of novel and efficient synthetic methods.

show abstract

Copper‐Catalyzed Oxidative [1+2+1+2] Cascade Cyclization of N,N‐Dimethyl Enaminones with Benzylamines: A Facile Access to Functionalized 1,4‐Dihydropyridines

Sun

Chai

Liu

et al. 2023

Chemistry A European J

View full text Add to dashboard Cite

Using benzylamines as the C4 source of 1,4dihydropyridines (1,4-DHPs), a Cu-catalyzed oxidative [1 + 2 + 1 + 2] cascade cyclization for the synthesis of 1,4-DHPs was firstly developed. A broad range of easily available N,Ndimethyl enaminones and benzylamines are employed smoothly to provide a diverse range of 1,4-DHPs with high efficiency. This method is performed by a one-pot cascade C(sp 3 )À H bond functionalization/C(sp 3 )À N cleavage/cyclization strategy to form simultaneously two C(sp 3 )À C(sp 2 ) bonds, two C(sp 2 )À N bonds, and a 1,4-DHP ring.

show abstract

Nickel‐Catalyzed Tandem Ring Contraction of TEMPO and C−N Bond Transamination of Enaminones toward Amino Diversity of Enaminones

Cited by 10 publications

References 60 publications

Organic Synthesis Using Nitroxides

Organic Synthesis Using Nitroxides

Three-Component Fusion to Pyrazolo[5,1-a]isoquinolines via Rh-Catalyzed Multiple Order Transformation of Enaminones

Copper‐Catalyzed Oxidative [1+2+1+2] Cascade Cyclization of N,N‐Dimethyl Enaminones with Benzylamines: A Facile Access to Functionalized 1,4‐Dihydropyridines

Contact Info

Product

Resources

About