Sodium diphenylketyl alkylation by chiral electrophilic reagents

Hebert, Eric; Mazaleyrat, Jean‐Paul; Welvart, Z.

doi:10.1039/c39770000877

Cited by 9 publications

(11 citation statements)

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“…Supposedly, because of large affinity of Si for O favoring the formation of O-silylated products, no phenyl silylation was detected, as in the reaction of benzophenone anion radical with 2-bromooctane [74]. This is consistent with the fact that O atom in carbonyl anion radicals acts as a nucleophilic center while C-atom mostly intervenes in ET processes [75].…”

Section: Methylbenzoatesupporting

confidence: 67%

Nucleophilic displacement versus electron transfer in the reactions of alkyl chlorosilanes with electrogenerated aromatic anion radicals

Soualmi

Dieng

Ourari

et al. 2015

Electrochimica Acta

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cleophilic displacement versus electron transfer in the reactions of alkyl chlorosilanes with electrogenerated aromatic anion radicals. Electrochimica Acta, Elsevier, 2015, 158, pp.457-469 AbstractAnion radicals of a series of aromatic compounds (C 6 H 5 CN, C 6 H 5 COOEt, anthracene, 9,10-dimethyl-, 9,10-diphenyl-and 9-phenylanthracene, pyrene and naphthalene) react with trialkyl complex of hypercoordinated silicon with electroactive ligand was formed instead, whose reduction requires about 1 V less negative potentials than bipyridine itself.

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Section: Methylbenzoatesupporting

confidence: 67%

Nucleophilic displacement versus electron transfer in the reactions of alkyl chlorosilanes with electrogenerated aromatic anion radicals

Soualmi

Dieng

Ourari

et al. 2015

Electrochimica Acta

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“…As model compound for the aromatic radical anions we employed the electrochemically generated radical anion of anthracene, the nucleophilic and electron-donating abilities of which are well-known. [18][19][20] At the same time our previous studies had revealed that the product pattern for this radical anion would be strongly dependent on the mechanism; 19,20 while the S N 2 reaction leads to substitution in the 9 position of anthracene, all three positions, 1, 2 and 9, are accessible for the ET mechanism.…”

Section: Introductionmentioning

confidence: 87%

“…[18][19][20] In the reaction between the radical anion of anthracene and optically active 2-octyl iodide, bromide and chloride it was found that the S N 2 component constituted 5, 8 and 11%, respectively, at room temperature. 18 Recently, it was reported that the S N 2 pathway for the reaction between a number of radical anions and alkyl halides could even be the dominant one as determined from leaving group effects and substitution patterns of the products formed. 19,20 For the reaction between the radical anion of anthracene and chloromethane, the S N 2 component was estimated to constitute as much as 97%.…”

Section: Introductionmentioning

confidence: 99%

“…In fact, in the literature only one report has appeared concerning product studies of the reaction between the radical anion of anthracene and optically active 2-octyl halides at two different temperatures, where a lowering of temperature was found to favour the S N 2 mechanism. 18 In the present paper our aim is to present a systematic study of the temperature dependency of the competition between the two reaction pathways in order to extract the pertinent activation parameters. Since the previous studies showed that the competition exists mainly for methyl halides and primary and secondary alkyl halides we selected cyclopropylmethyl bromide as a model compound.…”

Section: Introductionmentioning

confidence: 99%

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Activation parameters for the competing electron transfer and SN2 pathways of the reaction of anthracene radical anion with cyclopropylmethyl bromide

Jensen

Sørensen

Pedersen

et al. 2002

J. Chem. Soc., Perkin Trans. 2

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The reaction between the electrogenerated radical anion of anthracene and alkyl halides has been studied in the temperature interval of Ϫ50 to 40 ЊC in N,N-dimethylformamide in order to describe in detail the competition between the electron transfer (ET) and S N 2 pathways. For cyclopropylmethyl bromide the competition can be quantified directly on the basis of an analysis of the distribution of ring-opened versus ring-closed products. In general, the ET pathway is found to prevail although the S N 2 pathway becomes of greater importance as the temperature is lowered. When the product analysis is combined with the measurement of the overall rate constant for the reaction the pertinent activation parameters can be extracted for both mechanisms. As expected ∆H ‡ S N 2 is smaller than ∆H ‡ ET (by 7 kJ mol Ϫ1 ) because of the stronger bonding interaction present in the transition state of S N 2. On the other hand, this effect is more than counterbalanced by the fact that ET is entropically favoured because of smaller geometrical restrictions (∆S ‡ ET Ϫ ∆S ‡ S N 2 = 37 J mol Ϫ1 K Ϫ1 ). The S N 2 mechanism leads to substitution in the 9 position of anthracene while for the ET mechanism it takes place in all three positions of 1, 2 and 9. The overall distribution of products in the three positions is largely independent of temperature. This is due to the fact that the increased amount of S N 2 products formed in the 9 position as the temperature is lowered is accompanied by an equally large decrease in the amount of ET products obtained in the very same position. Exactly the same constancy in the product distribution is seen for the reaction of anthracene radical anion with bromoethane, where both mechanisms also exist. For the reaction involving the sterically hindered 1-iodoadamantane, on the other hand, the S N 2 pathway is precluded and in this case there is a profound decrease in the amount of 9-substitution as the temperature is lowered.

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“…8 Other techniques such as measuring certain ratios of products have also established the ratio of reactions 1 and 2 rate constants, for example for anthracene radical anions reacting with methyl halides. 9 Another feature of S N 2 reactions is the "cross-relation", which relates rate constants of "cross-reactions" to identity reactions (a relation that played a prominent role 10,11a,c in the interaction of theory and experiment for electron transfer reactions).…”

Section: Introductionmentioning

confidence: 99%

Theory of Rates of S_N2 Reactions and Relation to Those of Outer Sphere Bond Rupture Electron Transfers

Marcus

1997

J. Phys. Chem. A

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A model is considered for S N 2 reactions, based on two interacting states. Relevant bond energies, standard electrode potentials, solvent contributions (nonequilibrium polarization), and steric effects are included. A unified approach is introduced in which there can be a flux density for crossing the transition state, which is either bimodal, one part leading to S N 2 and the other to ET products, or unimodal with a less marked energydependent separation of the rates of formation of these products. In a unified description an expression is given for the reorganization energy, which reduces in the appropriate limits to the pure S N 2 and ET/bond rupture cases. Expressions are obtained for the S N 2 rate constant and for its relation to that of the concerted electron transfer/bond rupture reaction. Applications of the theory are made to the cross-relation between rate constants of cross and identity reactions, experimental entropies and energies of activation, the relative rates of S N 2 and ET reactions, and the possible expediting of an outer sphere ET reaction by an incipient S N 2-type interaction. Results on the photoelectron emission threshold energies of ions in solution provide some information on a solvation term, and another quantity can be estimated using data from gas phase S N 2 reactions or from quantum chemistry calculations. Also introduced for comparison is an adiabatic model that is an extension of a bond energy-bond order formulation for gas phase reactions.

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Sodium diphenylketyl alkylation by chiral electrophilic reagents

Cited by 9 publications

References 0 publications

Nucleophilic displacement versus electron transfer in the reactions of alkyl chlorosilanes with electrogenerated aromatic anion radicals

Nucleophilic displacement versus electron transfer in the reactions of alkyl chlorosilanes with electrogenerated aromatic anion radicals

Activation parameters for the competing electron transfer and SN2 pathways of the reaction of anthracene radical anion with cyclopropylmethyl bromide

Theory of Rates of S_N2 Reactions and Relation to Those of Outer Sphere Bond Rupture Electron Transfers

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Sodium diphenylketyl alkylation by chiral electrophilic reagents

Cited by 9 publications

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Nucleophilic displacement versus electron transfer in the reactions of alkyl chlorosilanes with electrogenerated aromatic anion radicals

Nucleophilic displacement versus electron transfer in the reactions of alkyl chlorosilanes with electrogenerated aromatic anion radicals

Activation parameters for the competing electron transfer and SN2 pathways of the reaction of anthracene radical anion with cyclopropylmethyl bromide

Theory of Rates of SN2 Reactions and Relation to Those of Outer Sphere Bond Rupture Electron Transfers

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Theory of Rates of S_N2 Reactions and Relation to Those of Outer Sphere Bond Rupture Electron Transfers