Reactions of 1-haloadamantanes and ethylmercury chloride with nitronate anions by the SRN1 mechanism

Santiago, Ana N.; Basso, Silvana M.; Toledo, Carlos A.; Rossi, Roberto A.

doi:10.1039/b418305c

Cited by 6 publications

(1 citation statement)

References 31 publications

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“…[30] 2) Quenching of the reaction by trace amounts of oxidising agents (e.g., p-dinitrobenzene, CuCl 2 ) or radical traps (e.g., di-tert-butyl nitroxide). [26,[31][32][33][34] 3) Entrainment of the reaction: [25,[35][36][37] for example, the anion of MeNO 2 does not react with 1-iodoadamantane under irradiation, but excellent yields of 1-adamantylnitromethane are obtained in the photostimulated reaction in Scheme 1. Extending this scheme to the formation of a Grignard reagent, the role of donor would be played by the active sites of the magnesium metallic surface (see text).…”

Section: Introductionmentioning

confidence: 97%

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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Section: Introductionmentioning

confidence: 97%

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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Radical‐Nucleophilic Aromatic Substitution

Rossi¹,

Guastavino²,

Budén³

2015

Arene Chemistry

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The S _RN 1 Reaction

Bardagi

Vaillard

Rossi

2012

Encyclopedia of Radicals in Chemistry, Biology and Materials

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Since its discovery, the radical nucleophilic substitution, or S RN 1 reaction, has been widely used to achieve new CC or C‐heteroatom bonds. The mechanism involves a chain propagation cycle with radicals and radical anions as intermediates. The initiation step is an electron transfer to a substrate to form its radical anion, which fragments to afford a radical and the anion of the leaving group. The radical thus formed couples with a nucleophile to give a new radical anion which, in the next propagation step, transfers its extra electron to the substrate, closing the cycle. Here we discuss S RN 1 reactions of aromatic substrates with carbanions and heteroaromatic nucleophiles as well as ring‐closure reactions to obtain heterocycles by different approaches. S RN 1 reactions of vinylic halides with nucleophiles and the competing mechanisms are also examined. Reactions of aliphatic substrates that do not react or are poorly reactive toward polar nucleophilic substitutions (cycloalkyl, bridgehead, neopentyl, and perfluoroalkyl halides) are discussed in terms of mechanistic requirements to follow an S RN 1 process. In addition, the reactions of alkyl substrates with electron‐withdrawing groups also are presented. Every year, new synthetic strategies and mechanistic studies involving S RN 1 reactions are reported, which constitute a useful tool in the field of organic chemistry.

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Reactions of 1-haloadamantanes and ethylmercury chloride with nitronate anions by the SRN1 mechanism

Cited by 6 publications

References 31 publications

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

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

Radical‐Nucleophilic Aromatic Substitution

The S _RN 1 Reaction

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Reactions of 1-haloadamantanes and ethylmercury chloride with nitronate anions by the SRN1 mechanism

Cited by 6 publications

References 31 publications

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

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

Radical‐Nucleophilic Aromatic Substitution

The S RN 1 Reaction

Contact Info

Product

Resources

About

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

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

The S _RN 1 Reaction