Arene‐catalyzed lithiation

Yus, Miguel

doi:10.1002/047002111x.ch11

Cited by 10 publications

(4 citation statements)

References 207 publications

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“…However, for further applications, sulfoxide should only be a chiral synthetic tool and must be disposed of at the end of the sequence . Among all the possible methods, the ligand exchange reaction of sulfoxides with alkylmetals is one of the most interesting transformations, although the sulfoxide cannot be reused, since further functionalization may increase the complexity of the carbon skeleton . In this context, we and others have recently described the unique preparation of vinylmetal derivatives from vinyl sulfoxides.…”

Section: Resultsmentioning

confidence: 99%

New Multicomponent Approach for the Creation of Chiral Quaternary Centers in the Carbonyl Allylation Reactions

Sklute

Marek

2006

J. Am. Chem. Soc.

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The combined regio- and stereo-controlled carbometalation reaction of alkynyl sulfoxide followed by a zinc homologation and finally an allylation reaction led, in a single-pot operation, to chiral homoallylic alcohols in excellent yields and diastereoselectivities for the creation of chiral quaternary and tertiary centers. The key features in all of the reactions that are described in this article are the high degree of stereocontrol, the level of predictability, and "the ease of execution" which ensures success in the application of such methods. The chiral sulfinyl moiety can be finally removed by simple treatment with alkyllithiums, which allows further functionalizations of the carbon skeleton. By using one of these methods, the creation of chiral quaternary centers with the smallest possible difference, namely CD3 versus CH3 and 13CH3 versus CH3, was easily performed.

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Section: Resultsmentioning

confidence: 99%

New Multicomponent Approach for the Creation of Chiral Quaternary Centers in the Carbonyl Allylation Reactions

Sklute

Marek

2006

J. Am. Chem. Soc.

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“…Early studies on the lithiation of ACPs followed by quenching of the organometal intermediates with electrophiles were carried out by Maercker et al and suggested the formation of dilithiated intermediates at the C–C double bond, which may undergo subsequent rearrangements including cyclopropane ring-opening and transfer of the lithium to more stabilized carbanion centers . Recent findings reported by Yus documented a change in regioselectivity, when the dilithiated species were generated according to the arene-catalyzed lithiation technology instead of with Li metal only. Indeed, treatment of 2,2-diphenylmethylenecyclopropane ( 688 ) with excess lithium metal, or also with lithium in the presence of catalytic naphthalene at room temperature, followed by quenching with water, furnished 4,4-diphenylbut-1-ene ( 699 ), apparently derived from the dilithiobutene 698 formed by cleavage of the proximal C–C bond with the substituted carbon of 688 .…”

Section: Alkylidenecyclopropanesmentioning

confidence: 99%

Progress in the Synthesis and Transformations of Alkylidenecyclopropanes and Alkylidenecyclobutanes

et al. 2014

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“…[95][96][97] Nevertheless, for the formation of organolithium compounds from the appropriate alkyl halide, mediators have repeatedly been used. [98][99][100][101] Their actual role as mediator has recently been established by electrochemical studies. [102] Test 7) The participation of radical intermediates in the preparation of Grignard reagents has been established beyond any doubt by spin-trapping, radical clocks, the nature of the byproducts formed and CIDNP.…”

Section: Introductionmentioning

confidence: 99%

About the Inhibition of Grignard Reagent Formation by p‐Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the S_RN1 Mechanism

et al. 2010

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Both SRN1‐type reactions and Grignard reagent formation are inhibited by trace amounts (with respect to the halide) of p‐dinitrobenzene (DNB) and other oxidising agents such as CuCl2 or dioxygen. Both are believed to be triggered by an electron‐transfer step. In this report we examine the patterns of reactivity shared by these two types of reaction. Although the two reactions display an amazing number of similarities, the chain character of the Grignard reaction mechanism has been rejected by major contributors to this field. We have performed new experiments to explore the inhibiting effect associated with the addition of trace amounts of p‐dinitrobenzene during Grignard reagent formation. This inhibition involves very reactive nanoparticles of magnesium prepared by metal vapour synthesis. The magnesium slurries studied, in the absence of p‐dinitrobenzene, display no induction period at all. If the p‐dinitrobenzene is added to the solution containing magnesium slurries 25 min before adding the organic halide (here bromobenzene), the reaction is neatly inhibited but, if one waits long enough, the Grignard reagent is nevertheless formed. If, however, the same trace amounts of p‐dinitrobenzene are diluted in the organic halide and this mixture is added to the magnesium slurries, the inhibiting effect is far less pronounced. The addition of the nBu4NBr salt drastically diminishes the inhibiting power of DNB. These observations, in addition to the ESR study of radical anions formed in THF by the reaction of magnesium nanoparticles and DNB with various polyaromatics, suggest a mechanism for the observed inhibitions that involves a series of reversible adsorptions of the present species. This adsorption would depend on both thermodynamic and kinetic factors. Thermodynamics would favour the adsorption of DNB radical anions but C–X bond cleavage of the less strongly adsorbed aromatic radical anions would provide a kinetic driving force for displacing the equilibria in the direction of Grignard reagent formation. Salt effects could operate by displacing the equilibrium – adsorbed DNB radical anion or dianion versus solvated radical anion (with the counterion nBu4N+) – to the right, accelerating therefore the liberation of active sites on the magnesium surface. It appears that the inhibiting effect of the same compound finds its origin in two different molecular series of events in SRN1 and in Grignard reagent formation. The heterogeneous character of the Grignard reagent makes it possible to envision the possibility of active sites even on nanoparticles, whereas the inhibition of the SRN1 mechanism by DNB occurs in homogeneous solution.

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Arene‐catalyzed lithiation

Cited by 10 publications

References 207 publications

New Multicomponent Approach for the Creation of Chiral Quaternary Centers in the Carbonyl Allylation Reactions

New Multicomponent Approach for the Creation of Chiral Quaternary Centers in the Carbonyl Allylation Reactions

Progress in the Synthesis and Transformations of Alkylidenecyclopropanes and Alkylidenecyclobutanes

About the Inhibition of Grignard Reagent Formation by p‐Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the S_RN1 Mechanism

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Arene‐catalyzed lithiation

Cited by 10 publications

References 207 publications

New Multicomponent Approach for the Creation of Chiral Quaternary Centers in the Carbonyl Allylation Reactions

New Multicomponent Approach for the Creation of Chiral Quaternary Centers in the Carbonyl Allylation Reactions

Progress in the Synthesis and Transformations of Alkylidenecyclopropanes and Alkylidenecyclobutanes

About the Inhibition of Grignard Reagent Formation by p‐Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the SRN1 Mechanism

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About the Inhibition of Grignard Reagent Formation by p‐Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the S_RN1 Mechanism