α-Arylation of Esters Catalyzed by the Pd(I) Dimer {[P(t-Bu)3]PdBr}2

Hama, Takuo; Hartwig, John F.

doi:10.1021/ol8002578

Cited by 93 publications

(37 citation statements)

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“…Although a variety of electronically varied aryl bromides reacted with the alkali metal enolates in good yields, 25,27,28 the coupling of alkali metal enolates of methyl isobutyrate with ortho -substituted aryl bromides do not occur. Furthermore, the high nucleophilicity of alkali metal enolates of methyl isobutyrate limits reactions of aryl bromides containing electrophilic functionality.…”

Section: Introductionmentioning

confidence: 98%

“…15,16 A variety of reactions of ketone, 17-22 ester, 23-28 amide, 29-32 and aldehyde 33,34 enolates have now been reported, but the use of strongly basic and nucleophlic alkali metal enolates limits the scope of these reactions. In addition, the arylated product, which is more acidic than the reactant, quenches the starting enolate, and products from undesired diarylation have formed.…”

Section: Introductionmentioning

confidence: 99%

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Palladium-Catalyzed α-Arylation of Zinc Enolates of Esters: Reaction Conditions and Substrate Scope

Hama

Hartwig

2013

J. Org. Chem.

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The intermolecular α-arylation of esters by palladium-catalyzed coupling of aryl bromides with zinc enolates of esters is reported. Reactions of three different types of zinc enolates have been developed. α-Arylation of esters occurs in high yields with isolated Reformatsky reagents, with Reformatsky reagents generated from α-bromo esters and activated zinc, and with zinc enolates generated by quenching lithium enolates of esters with zinc chloride. The use of zinc enolates, instead of alkali metal enolates, greatly expands the scope of the arylation of esters. The reactions occur at room temperature or at 70 °C with bromoarenes containing cyano, nitro, ester, keto, fluoro, enolizable hydrogen, hydroxyl or amino functionality and with bromopyridines. The scope of esters encompasses acyclic acetates, propionates, and isobutyrates, α-alkoxyesters, and lactones. The arylation of zinc enolates of esters was conducted with catalysts bearing the hindered pentaphenylferrocenyl di-tert-butylphosphine (Q-phos) or the highly reactive dimeric Pd(I) complex {[P(t-Bu)3]PdBr}2.

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Palladium-Catalyzed α-Arylation of Zinc Enolates of Esters: Reaction Conditions and Substrate Scope

Hama

Hartwig

2013

J. Org. Chem.

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“…Pd I -Komplexe, obwohl gegenwärtig nicht sehr geläufig, sind isolierbare dimere Spezies, die in Buchwald-HartwigAminierungen [10] und Enolat-Arylierungen Anwendung gefunden haben; [11] Die umgekehrte Reaktion, die polare MarkownikowAddition von HCl an Olefine, wird trotz der Nützlichkeit von Alkylchloriden kaum in der Synthese angewendet. Carreira und Gaspar berichteten jetzt über eine cobaltkatalysierte Addition, die wahrscheinlich über Radikalintermediate verläuft (Schema 6).…”

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Radikale und Übergangsmetallkatalyse – eine Allianz par excellence zur Steigerung von Reaktivität und Selektivität in der organischen Chemie

Ford¹,

Jahn²

2009

Angewandte Chemie

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Willkommen in der Radikalkatalyse: Durch Einbindung in Übergangsmetallkatalysezyklen „gezähmte“ Radikale beschleunigen den Gesamtprozess: in Minuten beendete Kumada‐Kupplungen (siehe Schema), hoch regioselektive cobaltkatalysierte Eliminierungen und Markownikow‐Additionen oder durch Titan‐Rhodium‐Systeme katalysierte reduktive Epoxidöffnungen – alle werden durch die hohe Reaktivität von Radikalintermediaten im Zyklus eines übergangsmetallkatalysierten Prozesses angetrieben.

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“…Mechanistic investigations confirmed that the generated enolate participated in the palladium-catalyzed coupling cycle, giving the α-arylated product. Later, [PdBrP(t-Bu) 3 ] 2 was also found to catalyze gram-scale α-arylation of methyl and t-butyl esters with aryl bromides under the conditions of method B [25].…”

Section: Cross-coupling Reactions Of Lithium Enolatesmentioning

confidence: 99%

Lithium Compounds in Cross‐Coupling Reactions

Shimizu

2014

Lithium Compounds in Organic Synthesis

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IntroductionTransition-metal-catalyzed cross-coupling reactions of organic halides with organometallic compounds have been recognized as one of the most powerful, practical, and versatile methods for carbon-carbon bond formation [1]. Various organometallic reagents such as organomagnesium (Grignard reagents), -zinc, -tin, -boron, and -silicon compounds are extensively studied and applied to the concise synthesis of natural products, biologically active substances, and functional materials [2]. On the other hand, the cross-coupling reactions of organolithium compounds are less developed compared to those of the organometals listed above probably because the high reactivity of lithium can cause side reactions such as halogen-lithium exchange and deprotonation of organic halides seriously and result in the narrow compatibility of functional groups [3]. Organolithium compounds are often used as typical precursors of the other organometallic reagents. Accordingly, it is highly desirable to use organolithium compounds as nucleophiles directly for transition-metal-catalyzed cross-coupling reactions in view of atom economy as well as the reduction of chemical waste, money, and time. As shown in Scheme 16.1, this chapter is divided into four sections based on the types of lithium compounds that participate in the cross-coupling reactions: (i) organolithium reagents in which a lithium atom is attached to a carbon atom, (ii) lithium enolates, (iii) lithium amides, and (iv) lithium thiolates. Described in Section 16.2 are cross-coupling reactions of aryl-, alkenyl-, and alkyllithiums with halogenated compounds. Section 16.3 summarizes the coupling reactions of lithium enolates with organic halides. Amination of aryl halides with lithium amides is reviewed in Section 16.4. Finally, thioether synthesis by coupling reaction using lithium thiolates as nucleophiles is described in Section 16.5. Throughout this chapter, molecular structures of lithium compounds, their precursors, and the molecular fragments originating from the lithium compounds in the products are drawn with thick bonds and atom labels in bold.

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α-Arylation of Esters Catalyzed by the Pd(I) Dimer {[P(t-Bu)₃]PdBr}₂

Cited by 93 publications

References 19 publications

Palladium-Catalyzed α-Arylation of Zinc Enolates of Esters: Reaction Conditions and Substrate Scope

Palladium-Catalyzed α-Arylation of Zinc Enolates of Esters: Reaction Conditions and Substrate Scope

Radikale und Übergangsmetallkatalyse – eine Allianz par excellence zur Steigerung von Reaktivität und Selektivität in der organischen Chemie

Lithium Compounds in Cross‐Coupling Reactions

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