Split Personality of Lithium Chloride: Recent Salt Effects in Organometallic Recipes

Hevia, Eva; Mulvey, Robert E.

doi:10.1002/anie.201102054

Cited by 99 publications

(46 citation statements)

References 29 publications

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“…[13] In a pioneering investigation, Negishi and co-workers showed that LiX and MgX 2 can significantly change the efficiency of the Pd-catalyzed cross-coupling reactions of aryl and alkenyl iodides with RZnX reagents. [14] The Organ group screened various salt additives in the Pd-mediated reaction of alkyl halides with BuZnBr and found that LiBr led to the largest rate enhancement.…”

Section: Introductionmentioning

confidence: 99%

Catalyst Activation, Deactivation, and Degradation in Palladium‐Mediated Negishi Cross‐Coupling Reactions

Böck

Feil

Karaghiosoff

et al. 2015

Chemistry A European J

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Pd-mediated Negishi cross-coupling reactions were studied by a combination of kinetic measurements, electrospray-ionization (ESI) mass spectrometry, (31)P NMR and UV/Vis spectroscopy. The kinetic measurements point to a rate-determining oxidative addition. Surprisingly, this step seems to involve not only the Pd catalyst and the aryl halide substrate, but also the organozinc reagent. In this context, the ESI-mass spectrometric observation of heterobimetallic Pd-Zn complexes [L2 PdZnR](+) (L=S-PHOS, R=Bu, Ph, Bn) is particularly revealing. The inferred presence of these and related neutral complexes with a direct Pd-Zn interaction in solution explains how the organozinc reagent can modulate the reactivity of the Pd catalyst. Previous theoretical calculations by González-Pérez et al. (Organometallics- 2012, 31, 2053) suggest that the complexation by the organozinc reagent lowers the activity of the Pd catalyst. Presumably, a similar effect also causes the rate decrease observed upon addition of ZnBr2 . In contrast, added LiBr apparently counteracts the formation of Pd-Zn complexes and restores the high activity of the Pd catalyst. At longer reaction times, deactivation processes due to degradation of the S-PHOS ligand and aggregation of the Pd catalyst come into play, thus further contributing to the appreciable complexity of the title reaction.

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Section: Introductionmentioning

confidence: 99%

Catalyst Activation, Deactivation, and Degradation in Palladium‐Mediated Negishi Cross‐Coupling Reactions

Böck

Feil

Karaghiosoff

et al. 2015

Chemistry A European J

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“…The previous investigation evaluating the effect of ligands clearly underlined influences of such compounds on the reactivity of organolithiums . In this context, “salt effects” have attracted significant interest in recent years, leading to comprehensive spectroscopic and theoretical investigations, more specifically in organolithium chemistry where the effects of lithium halides are commonly encountered . Lithium salts are undoubtedly among the most widely studied salts, being ubiquitous in a large number of lithiation reactions – either because they are generated in the reaction, or because they are involuntarily brought by a contaminated commercial source.…”

Section: Resultsmentioning

confidence: 99%

Transition‐Metal‐Free Heterobiaryl Synthesis via Aryne Coupling

et al. 2019

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“…It should be noted that the negative effect of LiCl on deprotonation contrasts with its positive influence on the Br/Mg exchange process (Scheme ) 30. The dual, positive or negative, influence of the LiCl salt on the reaction course is an increasingly observed phenomenon 38…”

Section: Resultsmentioning

confidence: 99%

Sequential Synthesis of Organosilicon‐Linked 2‐Methoxypyridines by Non‐Cryogenic ortho‐Metallation Using the nBu₂TMPMg·Li Reagent and Hydrosilylation

et al. 2016

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The non‐cryogenic synthesis of 5/6‐ and/or 3‐silyl‐functionalised 2‐methoxypyridines by a 5‐Br/Mg exchange process using nBu2iPrMg Li and LiCl and involving C‐3 metallation using a novel nBu2TMPMg Li reagent is described. Furthermore, the usefulness of nBu2TMPMg Li in the functionalisation of 2‐methoxypyridine at the 3‐position with a wide range of electrophiles was successfully tested. The above achievements have allowed the construction of organosilicon‐linked 2‐methoxypyridines composed of two, three and four rings by the hydrosilylation of 5‐ and/or 3‐SiH(or alkenyl) derivatives using the hitherto rarely applied [Pt(cod)Me2] catalyst. Additionally, the synthesis of a one‐chain oligomer consisting of eight 2‐methoxypyridines obtained by the hydrosilylation/polymerisation approach, followed by protodesilylation of the SiHMe2 group was also achieved by manipulating the amount of catalyst in the reactions.

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Split Personality of Lithium Chloride: Recent Salt Effects in Organometallic Recipes

Cited by 99 publications

References 29 publications

Catalyst Activation, Deactivation, and Degradation in Palladium‐Mediated Negishi Cross‐Coupling Reactions

Catalyst Activation, Deactivation, and Degradation in Palladium‐Mediated Negishi Cross‐Coupling Reactions

Transition‐Metal‐Free Heterobiaryl Synthesis via Aryne Coupling

Sequential Synthesis of Organosilicon‐Linked 2‐Methoxypyridines by Non‐Cryogenic ortho‐Metallation Using the nBu₂TMPMg·Li Reagent and Hydrosilylation

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Split Personality of Lithium Chloride: Recent Salt Effects in Organometallic Recipes

Cited by 99 publications

References 29 publications

Catalyst Activation, Deactivation, and Degradation in Palladium‐Mediated Negishi Cross‐Coupling Reactions

Catalyst Activation, Deactivation, and Degradation in Palladium‐Mediated Negishi Cross‐Coupling Reactions

Transition‐Metal‐Free Heterobiaryl Synthesis via Aryne Coupling

Sequential Synthesis of Organosilicon‐Linked 2‐Methoxypyridines by Non‐Cryogenic ortho‐Metallation Using the nBu2TMPMg·Li Reagent and Hydrosilylation

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Product

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Sequential Synthesis of Organosilicon‐Linked 2‐Methoxypyridines by Non‐Cryogenic ortho‐Metallation Using the nBu₂TMPMg·Li Reagent and Hydrosilylation