Pd-Catalyzed α-Arylation of Nitriles and Esters and γ-Arylation of Unsaturated Nitriles with TMPZnCl·LiCl

Duez, Stéphanie; Bernhardt, Sebastian; Heppekausen, Johannes; Fleming, Fraser F.; Knöchel, Paul

doi:10.1021/ol200194y

Cited by 77 publications

(32 citation statements)

References 55 publications

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“…[12,13] Besides, 7 proved to be an excellent base for the generation of nitrile and ester enolates. [13,14] We have also demonstrated that 7 is compatible with additional strong Lewis acids (MgCl 2 , BF 3 ·OEt 2 ) and forms frustrated Lewis pairs.…”

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confidence: 66%

Lewis Acid Promoted Benzylic Cross‐Couplings of Pyridines with Aryl Bromides

et al. 2011

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confidence: 66%

Lewis Acid Promoted Benzylic Cross‐Couplings of Pyridines with Aryl Bromides

et al. 2011

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“…The residual bromide in 30 allowed for the rapid attachment of the entire ester side chain by a palladium‐catalyzed enolate arylation reaction. After some experimentation, it was found that this transformation was best achieved by deprotonation of acetate 31 with TMPZnCl⋅LiCl, followed by palladium‐catalyzed cross‐coupling of the resulting enolate 51. Gratifyingly, the resulting diyne derivative 32 could be cyclized in good yield by RCAM, although the somewhat less encumbered complex 6 (Scheme ), activated in situ on treatment with CH 2 Cl 2 as previously described by our group,52 had to be used for optimal results 53.…”

Section: Resultsmentioning

confidence: 99%

Increasing the Structural Span of Alkyne Metathesis

Persich

Llaveria

Lhermet

et al. 2013

Chemistry A European J

104

116

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A new generation of alkyne metathesis catalysts, which are distinguished by high activity and an exquisite functional group tolerance, allows the scope of this transformation to be extended beyond its traditional range. They accept substrates that were previously found problematic or unreactive, such as propargyl alcohol derivatives, electron-deficient and electron-rich acetylenes of various types, and even terminal alkynes. Moreover, post-metathetic transformations other than semi-reduction increase the structural portfolio, as witnessed by the synthesis of a annulated phenol derivative via ring-closing alkyne metathesis (RCAM) followed by a transannular gold-catalyzed Conia-ene reaction. Further examples encompass a post-metathetic transannular ketone-alkyne cyclization with formation of a trisubstituted furan, a ruthenium-catalyzed redox isomerization, and a Meyer-Schuster rearrangement/oxa-Michael cascade. These reaction modes fueled model studies toward salicylate macrolides, furanocembranolides, and the cytotoxic macrolides acutiphycin and enigmazole A; moreover, they served as the key design elements of concise total syntheses of dehydrocurvularin (27) and the antibiotic agent A26771B (36).

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“…39 Most recently, Knochel reported three examples of palladium-catalyzed α-arylation reactions of zinc ester enolates. 40 These zinc enolates are formed by reaction of ethyl butyrate or isobutyrate with (TMP)ZnCl•LiCl. Because palladium-catalyzed α-arylation of alkali metal enolates occurred in high yields in the presence of catalyst systems bearing sterically hindered, electron-rich alkylphosphines, 24,26-28,31 we sought to develop general procedures for the palladium-catalyzed α-arylation of Reformatsky reagents.…”

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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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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Pd-Catalyzed α-Arylation of Nitriles and Esters and γ-Arylation of Unsaturated Nitriles with TMPZnCl·LiCl

Abstract: Using TMPZnCl·LiCl as a kinetically highly active base, nitriles and esters undergo a Pd-catalyzed α-arylation under mild conditions. Remarkably, in the case of α,β- or β,γ-unsaturated nitriles, a regioselective γ-arylation or a γ-alkenylation is observed.

Cited by 77 publications

References 55 publications

Lewis Acid Promoted Benzylic Cross‐Couplings of Pyridines with Aryl Bromides

Lewis Acid Promoted Benzylic Cross‐Couplings of Pyridines with Aryl Bromides

Increasing the Structural Span of Alkyne Metathesis

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

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