Selective Vinyl C−H Lithiation of <i>cis</i>-Stilbenes

Tricotet, Thomas; Fleming, Patricia; Cotter, Julian R.; Hogan, Andrew J.; Strohmann, Carsten; Gessner, Viktoria H.; O’Shea, Donal F.

doi:10.1021/ja809941n

Cited by 48 publications

(20 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…(Trimethylsilyl)methylrubidium was produced by a reaction of the corresponding bisalkylmercury with rubidium metal and used in a subsequent benzylic metalation of benzyltrimethylsilane. [25] The work reported herein describes the preparation and isolation of (trimethylsilyl)methylrubidium and (trimethylsilyl)methylcesium, and their subsequent employment in the synthesis of the corresponding TMP compounds, which were structurally characterised as TMEDA (N,N,NЈ,NЈ-tetramethylethylenediamine)-supported solvates. [24] This approach can be considered either as a combination of a metalation of the amine by the alkyllithium followed by a metathesis reaction, or as producing the corresponding alkali metal alkyl compound from the corresponding tert-butoxide, which then performs the direct metalation of the amine.…”

Section: Introductionmentioning

confidence: 99%

Adding Rubidium and Cesium to the Homologous Series of Alkali Metal Compounds of (Trimethylsilyl)methanides and 2,2,6,6‐Tetramethylpiperidides

et al. 2012

View full text Add to dashboard Cite

Keywords: Alkali metals / Metalation / Rubidium / Cesium / Carbanions / N-donor ligands (Trimethylsilyl)methylrubidium [RbCH 2 SiMe 3 ] (1) and (trimethylsilyl)methylcesium [CsCH 2 SiMe 3 ] (2) were prepared by metathesis reactions of (trimethylsilyl)methyllithium [LiCH 2 SiMe 3 ] with rubidium or cesium tert-butoxide in nhexane. Both new compounds are pyrophoric powders which were characterised by NMR spectroscopy and elemental analyses. They can be used as deprotonating agents towards secondary amines such as 2,2,6,6-tetramethylpiperidine (TMPH). The resulting amides [RbTMP] (3) and [CsTMP] (4) form temperature-sensitive, n-hexane-insoluble orange solids. Treatment with the bidentate donor N,N,NЈ,NЈ-tetra- [a]

show abstract

Section: Introductionmentioning

confidence: 99%

Adding Rubidium and Cesium to the Homologous Series of Alkali Metal Compounds of (Trimethylsilyl)methanides and 2,2,6,6‐Tetramethylpiperidides

et al. 2012

View full text Add to dashboard Cite

show abstract

“…Surprisingly, there appears to have been no progress made in trying to merge ideas from each era, that is in constructing multicomponent TMP complexes8 based on mixed alkali-metal–alkali-metal pairings, a fact made all the more perplexing because hetero-alkali-metal imide,9 alkoxide,10 primary amide,11 heteroanionic alkoxide/primary amide12 and other secondary amide13 complexes have all received attention. The excellent recent studies of O’Shea et al have implicated TMP in a hetero-alkali-metal base for performing selective vinyl14 and alkyl/aryl15 deprotonation in a series of substituted toluenes, albeit using a heteroanionic alkyl/alkoxide/amide base. The empty file on hetero-(alkali-metal)–TMP chemistry is all the more extraordinary given the comprehensive dossier amassed for LiTMP16 (and to a much lesser extent for NaTMP17) and the fact that 20 years have passed since Williard and Nichols established a hetero-(alkali-metal) chemistry of HMDS18 (HMDS=1,1,1,3,3,3-hexamethyldisilazide), another utility amide though a much less powerful base than LiTMP.…”

Section: Introductionmentioning

confidence: 99%

Developing a Hetero‐Alkali‐Metal Chemistry of 2,2,6,6‐Tetramethylpiperidide (TMP): Stoichiometric and Structural Diversity within a Series of Lithium/Sodium, Lithium/Potassium and Sodium/Potassium TMP Compounds

Armstrong

Kennedy

Mulvey

et al. 2011

Chemistry A European J

View full text Add to dashboard Cite

Studied extensively in solution and in the solid state, Li(TMP) (TMP=2,2,6,6-tetramethylpiperidide) is an important utility reagent popular as a strongly basic, weakly nucleophilic tool for C–H metallation. Recently, there has been a surge in interest in mixed metal derivatives containing the bulky TMP anion. Herein, we start to develop hetero (alkali metal) TMP chemistry by reporting the N,N,N′,N′-tetramethylethylenediamine (TMEDA)-hemisolvated sodium–lithium cycloheterodimer [(tmeda)Na(μ-tmp)2Li], and its TMEDA-free variant [{Na(μ-tmp)Li(μ-tmp)}∞], which provides a rare example of a crystallographically authenticated polymeric alkali metal amide. Experimental observations suggest that the former is a kinetic intermediate en route to the latter thermodynamic product. Furthermore, a third modification, the mixed potassium–lithium-rich cycloheterotrimer [(tmeda)K(μ-tmp)Li(μ-tmp)Li(μ-tmp)], has also been synthesised and crystallographically characterised. On moving to the bulkier tridentate donor N,N,N′,N′′,N′′-pentamethyldiethylenediamine (PMDETA), the additional ligation forces the sodium–lithium and potassium–dilithium ring species to open giving the acyclic arc-shaped complexes [(pmdeta)Na(μ-tmp)Li(tmp)] and [(pmdeta)K(μ-tmp)Li(μ-tmp)Li(tmp)], respectively. Completing the series, the potassium–lithium and potassium–sodium derivatives [(pmdeta)K(μ-tmp)2M] (M=Li, Na) have also been isolated as closed structures with a distinctly asymmetric central MN2K ring. Collectively, these seven new bimetallic compounds display five distinct structural motifs, four of which have never hitherto been witnessed in TMP chemistry and three of which are unprecedented in the vast structural library of alkali metal amide chemistry.

show abstract

“…We recently reported that mixed Li/K metal TMP amide (LiNK metalation conditions) is uniquely suited for the selective achievement of challenging metalations. Specifically, the use of the reagent triad BuLi/KO t -Bu/TMP(H) to generate a mixed Li/K metal TMP amide in situ has proven to be an efficient and general method to achieve vinyl and benzylic metalations with excellent selectivity [6–7]. We now exploit this selective benzylic metalation protocol for the specific synthesis of [2.2]metacyclophanes.…”

Section: Introductionmentioning

confidence: 99%

Use of mixed Li/K metal TMP amide (LiNK chemistry) for the synthesis of [2.2]metacyclophanes

Blangetti

Fleming²,

O’Shea

2011

Beilstein J. Org. Chem.

Self Cite

View full text Add to dashboard Cite

SummaryA new two-step general approach to [2.2]metacyclophane synthesis from substituted m-xylenes is described. The strategy employs a selective benzylic metalation and oxidative C–C bond formation for both synthetic operations. Regioselective benzylic metalation is achieved using the BuLi, KOt-Bu, TMP(H) (2,2,6,6-tetramethylpiperidine) combination (LiNK metalation conditions) and oxidative coupling with 1,2-dibromoethane. The synthetic ease of this approach compares favourably with previously reported methods and allows for ready access to potentially useful planar chiral derivatives.

show abstract

Selective Vinyl C−H Lithiation of cis-Stilbenes

Cited by 48 publications

References 9 publications

Adding Rubidium and Cesium to the Homologous Series of Alkali Metal Compounds of (Trimethylsilyl)methanides and 2,2,6,6‐Tetramethylpiperidides

Adding Rubidium and Cesium to the Homologous Series of Alkali Metal Compounds of (Trimethylsilyl)methanides and 2,2,6,6‐Tetramethylpiperidides

Developing a Hetero‐Alkali‐Metal Chemistry of 2,2,6,6‐Tetramethylpiperidide (TMP): Stoichiometric and Structural Diversity within a Series of Lithium/Sodium, Lithium/Potassium and Sodium/Potassium TMP Compounds

Use of mixed Li/K metal TMP amide (LiNK chemistry) for the synthesis of [2.2]metacyclophanes

Contact Info

Product

Resources

About