Metal-Free Synthesis of Pyrrolo[1,2-a]quinoxalines Mediated by TEMPO Oxoammonium Salts

Huo, Hengrui; Tang, Xiang‐Ying; Gong, Yuefa

doi:10.1055/s-0037-1610131

Cited by 33 publications

(5 citation statements)

References 11 publications

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“…Oxidative dehydrogenation reactions using TEMPO derivatives or PINO were also used in various cyclization, annulation, and/or dehydrogenation reactions, and the synthesis of benzimidazoles, − benzoxazoles, , benzothiazoles, pyrazolopyridine, quinoxalines, , quinazolines, − quinazolinones, quinolines, , and quinolones and homocoupling of benzothiazoles were reported. As an example, a sequence including a dehydrogenation for the construction of the indolizine core is depicted in Scheme . − In this context, the amination of benzoxazoles and oxadiazoles was developed, where reactions proceed through initial amine addition onto the heteroarene with subsequent oxidative rearomatization (dehydrogenation) by an oxoammonium salt …”

Section: Oxidation Reactionsmentioning

confidence: 99%

“…Dehydrogenation reactions were also performed on indoline, tetrahydroquinoline, 684 dihydropyrimidinones, dihydropyrimidines, 685 dihydropyridines, and pyrazolines 686 using NHPI in cooperation with a copper or cobalt catalyst. Oxidative dehydrogenation reactions using TEMPO derivatives or PINO were also used in various cyclization, annulation, and/or dehydrogenation reactions, and the synthesis of benzimidazoles, 687−689 benzoxazoles, 690,691 benzothiazoles, 690 pyrazolopyridine, 692 quinoxalines, 693,694 quinazolines, 695−698 quinazolinones, 689 quinolines, 695,699 and quinolones 700 and homocoupling of benzothiazoles 701 were reported. As an example, a sequence including a dehydrogenation for the construction of the indolizine core is depicted in Scheme 27.…”

Section: Physical Properties and Reactivitymentioning

confidence: 99%

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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: Oxidation Reactionsmentioning

confidence: 99%

Section: Physical Properties and Reactivitymentioning

confidence: 99%

Organic Synthesis Using Nitroxides

Leifert

Studer

2023

Chem. Rev.

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“…It has gained prominence because substitution at C-4 pyrroloquinoxalines boosts its physiological properties like anticancer, antiviral, and antiproliferative effects. Various synthetic pathways have been developed to prepare pyrroloquinoxalines [42][43][44] because it is crucial in drug discovery. For this reason, an efficient method was established by Allan et al [45], which is an acid-catalyzed reaction for the synthesis of 4-aryl substituted pyrrolo[1,2-a] quinoxalines (24).…”

Section: Using the Catalytic Amount Of Acetic Acid And Aldehydesmentioning

confidence: 99%

Novel Synthetic Routes to Prepare Biologically Active Quinoxalines and Their Derivatives: A Synthetic Review for the Last Two Decades

Khatoon

Abdulmalek

2021

Molecules

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Quinoxalines, a class of N-heterocyclic compounds, are important biological agents, and a significant amount of research activity has been directed towards this class. They have several prominent pharmacological effects like antifungal, antibacterial, antiviral, and antimicrobial. Quinoxaline derivatives have diverse therapeutic uses and have become the crucial component in drugs used to treat cancerous cells, AIDS, plant viruses, schizophrenia, certifying them a great future in medicinal chemistry. Due to the current pandemic situation caused by SARS-COVID 19, it has become essential to synthesize drugs to combat deadly pathogens (bacteria, fungi, viruses) for now and near future. Since quinoxalines is an essential moiety to treat infectious diseases, numerous synthetic routes have been developed by researchers, with a prime focus on green chemistry and cost-effective methods. This review paper highlights the various synthetic routes to prepare quinoxaline and its derivatives, covering the literature for the last two decades. A total of 31 schemes have been explained using the green chemistry approach, cost-effective methods, and quinoxaline derivatives’ therapeutic uses.

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“…Pyrroloquinoixalines are tricyclic Mq derivatives, some of which have been demonstrated within the group to be acetylcholinesterase inhibitors (IC 50 = 2 µM). In terms of synthesis, there are several viable routes to tricyclic heterocycles, with reported examples including a Pictet-Spengler reaction [91] and Ullman coupling of pyrroles with nitroarenes [92]. Radical chemistry represents an attractive alternative thanks to its mild conditions and lack of necessity to protect functional groups [93].…”

Section: Novel Synthesis Of Pyrroloquinoxalines Using Sulfone Radicals (P09)mentioning

confidence: 99%

29th Annual GP2A Medicinal Chemistry Conference

et al. 2021

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The 29th Annual GP2A (Group for the Promotion of Pharmaceutical chemistry in Academia) Conference was a virtual event this year due to the COVID-19 pandemic and spanned three days from Wednesday 25 to Friday 27 August 2021. The meeting brought together an international delegation of researchers with interests in medicinal chemistry and interfacing disciplines. Abstracts of keynote lectures given by the 10 invited speakers, along with those of the 8 young researcher talks and the 50 flash presentation posters, are included in this report. Like previous editions, the conference was a real success, with high-level scientific discussions on cutting-edge advances in the fields of pharmaceutical chemistry.

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Metal-Free Synthesis of Pyrrolo[1,2-a]quinoxalines Mediated by TEMPO Oxoammonium Salts

Cited by 33 publications

References 11 publications

Organic Synthesis Using Nitroxides

Organic Synthesis Using Nitroxides

Novel Synthetic Routes to Prepare Biologically Active Quinoxalines and Their Derivatives: A Synthetic Review for the Last Two Decades

29th Annual GP2A Medicinal Chemistry Conference

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