Deaminative Reductive Cross-Electrophile Couplings of Alkylpyridinium Salts and Aryl Bromides

Liao, Jennie; Basch, Corey H.; Hoerrner, Megan E.; Talley, Michael R.; Boscoe, Brian P.; Tucker, Joseph W.; Garnsey, Michelle R.; Watson, Mary P.

doi:10.1021/acs.orglett.9b01014

Cited by 128 publications

(64 citation statements)

References 71 publications

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“…Although organometallic reagents constitute aw idely available class of nucleophilic cross-coupling partners,t he coupling of two electrophiles can offer several distinct advantages. [34] To this end, the groups of Rueping, [35] Watson, [36] and Martin [37] have independently developed an ickel-catalyzed reductive cross-coupling of C(sp 2 )h alides with N-alkyl pyridinium salts 1 (Scheme 4). Theconditions in all three methods differ slightly;h owever, Mn powder was identified as the optimal stoichiometric reductant in all cases and elevated temperatures were required in most examples.…”

Section: N-carbon-substituted Pyridinium Reagentsmentioning

confidence: 99%

Pyridinium Salts as Redox‐Active Functional Group Transfer Reagents

et al. 2020

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In this Review, we highlight recent advances in the understanding and design of N‐functionalized pyridinium scaffolds as redox‐active, single‐electron, functional group transfer reagents. We provide a selection of representative methods that demonstrate reactivity and fundamental advances in this emerging field. The reactivity of these reagents can be divided into two divergent pathways: homolytic fragmentation to liberate the N‐bound substituent as the corresponding radical or an alternative heterolytic fragmentation that liberates an N‐centered pyridinium radical. A short description of the elementary steps involved in fragmentation induced by single‐electron transfer is also critically discussed to guide readers towards fundamental processes thought to occur under these conditions.

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Section: N-carbon-substituted Pyridinium Reagentsmentioning

confidence: 99%

Pyridinium Salts as Redox‐Active Functional Group Transfer Reagents

et al. 2020

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“…We found that secondary alkyl pyridinium salts required modified conditions (Table and Tables S2.5–S2.7 in the Supporting Information). These secondary alkyl reagents typically undergo more facile C−N bond cleavage, thus making formation of dihydropyridine byproduct even more competitive . To avoid this byproduct, the following changes were made: 1) using 2‐pyridyl esters instead of acyl fluorides; 2) changing the solvent to THF and lowering the temperature; 3) switching the ligand to L4 (entry 2).…”

Section: Methodsmentioning

confidence: 99%

Nickel‐Catalyzed Synthesis of Dialkyl Ketones from the Coupling of N‐Alkyl Pyridinium Salts with Activated Carboxylic Acids

et al. 2020

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While ketones are among the most versatile functional groups, their synthesis remains reliant upon reactive and low‐abundance starting materials. In contrast, amide formation is the most‐used bond‐construction method in medicinal chemistry because the chemistry is reliable and draws upon large and diverse substrate pools. A new method for the synthesis of ketones is presented here that draws from the same substrates used for amide bond synthesis: amines and carboxylic acids. A nickel terpyridine catalyst couples N‐alkyl pyridinium salts with in situ formed carboxylic acid fluorides or 2‐pyridyl esters under reducing conditions (Mn metal). The reaction has a broad scope, as demonstrated by the synthesis of 35 different ketones bearing a wide variety of functional groups with an average yield of 60±16 %. This approach is capable of coupling diverse substrates, including pharmaceutical intermediates, to rapidly form complex ketones.

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“…Während metallorganische Reagenzien eine weit verbreitete Klasse von nukleophilen Kreuzkupplungspartnern darstellen, kann die Kupplung zweier Elektrophiler mehrere entscheidende Vorteile bieten . Zu diesem Zweck haben die Gruppen von Rueping, Watson und Martin unabhängig voneinander eine nickelkatalysierte, reduktive Kreuzkupplung von C(sp 2 )‐Halogeniden mit den N ‐Alkylpyridiniumsalzen 1 entwickelt (Schema ). Die Bedingungen bei allen drei Methoden unterscheiden sich leicht, jedoch wurde Mn‐Pulver in allen Fällen als das optimale stöchiometrische Reduktionsmittel identifiziert, und in den meisten Beispielen werden erhöhte Temperaturen benötigt.…”

Section: Pyridiniumsalze Als Reagenzien Zur üBertragung Funktionellerunclassified

Pyridiniumsalze als redoxaktive Reagenzien zur Übertragung funktioneller Gruppen

Rössler¹,

Jelier²,

Magnier

et al. 2020

Angewandte Chemie

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In diesem Aufsatz sind die jüngsten Fortschritte beim Verständnis und Design von N‐funktionalisierten Pyridiniumsalzen als redoxaktivierte Einelektronentransfer‐Reagenzien zur Übertragung funktioneller Gruppen zusammengefasst. Anhand einer Auswahl an repräsentativen Methoden werden Reaktivität und grundlegende Fortschritte in diesem sich rasch entwickelnden Bereich diskutiert. Diese Reagenzien weisen zwei grundsätzlich divergierende Reaktionspfade auf: homolytische Fragmentierung zur Freisetzung des N‐gebundenen Substituenten als entsprechendes Radikal oder eine alternative, heterolytische Fragmentierung zur Freisetzung eines radikalischen Pyridiniumkations. Die elementaren Schritte der durch Einelektronentransfer induzierten Fragmentierung werden kritisch diskutiert.

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Deaminative Reductive Cross-Electrophile Couplings of Alkylpyridinium Salts and Aryl Bromides

Cited by 128 publications

References 71 publications

Pyridinium Salts as Redox‐Active Functional Group Transfer Reagents

Pyridinium Salts as Redox‐Active Functional Group Transfer Reagents

Nickel‐Catalyzed Synthesis of Dialkyl Ketones from the Coupling of N‐Alkyl Pyridinium Salts with Activated Carboxylic Acids

Pyridiniumsalze als redoxaktive Reagenzien zur Übertragung funktioneller Gruppen

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