Radical Nucleophilic Substitution Mechanism Research Articles

Synthesis of α,α-diaryl nitriles by radical nucleophilic substitution

The present study shows that the anion of 2-naphthylacetonitrile is substituted selectively at its Cα by aromatic halides, through a radical nucleophilic substitution mechanism, to give the corresponding α,α-diaryl nitriles in good yields. The regioselectivity of this ambident nucleophile changes with the steric hindrance at the radical centre from the aromatic substrate. The selectivity observed was investigated through a computational model of the key reaction step.

Selective synthesis of mono- and distannylpyridines from chloropyridinols via an S RN1 mechanism

A selective two-step synthesis of either mono- or distannylated pyridines from commercially available pyridinols, involving its conversion to the corresponding diethyl pyridyl phosphates (pyDEP) followed by the reaction with Me 3SnNa in liquid ammonia, is described. The results obtained clearly indicate that the reactions proceed through an unimolecular radical nucleophilic substitution mechanism (S RN1) with intermediacy of a monosubstitution product.

ChemInform Abstract: Arylation of Heterocyclic Ketene Aminals with 2,4-Dinitrohalobenzenes by a Radical Nucleophilic Substitution Mechanism.

The anions of heterocyclic ketene aminals reacted with 2,4-dinitrohalobenzenes to give arylated products by a radical nucleophilic substitution mechanism. The SRN1 mechanism was confirmed by EPR spectroscopy, EPR spin trapping, and by depression of the reaction rate by the addition of an inhibitor.

Recent Advances on Radical Nucleophilic Substitution Reactions

The radical nucleophilic substitution mechanism or SRN1 is a chain process, in which radicals and radical anions are intermediates. This process has been extensively used to effect substitution on a wide variety of substrates. The SRN1 reaction has been studied from both mechanistic and synthetic standpoints. The SRN1 mechanism requires an initiation step. Spontaneous electron transfer (ET) from the nucleophile to the substrate has been observed in a few systems; light stimulation, electrodes, alkali metals or inorganic salt-mediation is used otherwise. There are systems that are totally inert or undergo rather slow substitutions by classical polar mechanisms. Their lack of reactivity is usually due to strain (cycloalkyl and polycycloalkyl halides), steric (cycloalkyl, polycycloalkyl and neopentyl halides), or electronic factors (unactivated aromatic, vinyl halides and perfluoroalkyl halides). For these families of compounds, the nucleophilic substitution can be accomplished by the SRN1 mechanism. Conversely, there is a class of substrates, for which substitution can be achieved through both polar and ET mechanisms; however, the ET pathway is favored in some systems (i.e.: alkyl halides with EWG). We propose to undertake a compilation and critical review on SRN1 reactions dealing with substitutions on aromatic substrates, cycloalkyl, bridgehead, neopentyl, vinyl halides, perfluoroalkyl iodides, aliphatic substrates with EWG in the _ position and N,N-Dialkyl-p-toluenesulfonamides. With this aim in mind, we expect to cover recent SRN1 substitutions, with an emphasis on the scope of the process in terms of synthetic capability and target applications.

Effects of electron acceptors and radical scavengers on nonchain radical nucleophilic substitution reactions

The yields of reaction products from thermal nucleophilic substitution reactions in dimethyl sulfoxide (DMSO) of six o- and p-nitrohalobenzenes with the sodium salt of ethyl [alpha]-cyanoacetate carbanion [Na[sup +][sup [minus]]CH(CN)CO[sub 2]Et] were found to be markedly diminished by addition of small amounts of strong electron acceptors (p-dinitrobenzene, m-dinitrobenzene, and o-dinitrobenzene), but little or no diminished effects on the yields of reaction products were observed by addition of radical scavengers (such as galvinoxyl, nitroxyl, etc.). The results are consistent with the conclusion that these reactions proceed via a nonchain radical nucleophilic substitution mechanism. 28 refs., 3 tabs.

Arylation of heterocyclic ketene aminals with 2,4-dinitrohalobenzenes by a radical nucleophilic substitution mechanism

The anions of heterocyclic ketene aminals reacted with 2,4-dinitrohalobenzenes to give arylated products by a radical nucleophilic substitution mechanism. The SRN1 mechanism was confirmed by EPR spectroscopy, EPR spin trapping, and by depression of the reaction rate by the addition of an inhibitor.

Kinetics and mechanism of the reactions of o- and p-nitrohalobeszenes with the sodium salt of ethyl cyanoacetate carbanion: a non-chain radical nucleophilic substitution mechanism

The nucleophilic substitution reactions of o-nitroehlorobenzene (1a), o-nitrobromobenzene (lb), p-nitrofluorobenzene (1c), p-nitrochlorobenzene (1d), p-nitrobromobenzene (1e), and p-nitroiodobenzene (1f) with the sodium salt of ethyl cyanoaceaate carbanion (2) in DMSO all gave the corresponding substitution producss in almost quantitative yields. With the exception of the reaction of 1c with 2, the ESR spectra for the corresponding reactive intermediates, the radical anions of nitrophenyl halides were recorded. The relative intensity of ESR absorption versus time curves at various temperatures for the o-nitrochlorobenzene radical anion (3a), p-nitrochlorobenzene radical anion(3d), and p-nitrobromobenzene radical anion (3e) formed in the reactions of 1a, 1d, and 1e with 2 respectively in DMSO were measured by means of an ESR F/F lock technique. The kinetic curves obtained are consistent with the successive pseudo first-order reaction, and the rate constanss for the single electron transfer reactions of 1a, 1d, and 1e with 2 respectively and for the dissociation reactions of 3a, 3d, and 3e and the corresponding activaiion parameters were calculated. The results provide conclusive evidence that the thermal reactions of o- and p-nitrohalobenzeses (with the possible exception of 1c) with 2 proceed via a non-chann radical nucleophilic substitution mechanism.

Radical nucleophilic substitution mechanism in the reactions of arenediazonium cations with nitrite ion

Abstract Reactions of arenediazonium cations with nitrite ion generally believed to involve nucleophilic displacement have been found to occur via single electron transfer where free radicals intervene.

The S RN2 mechanism of nucleophilic substitution

1-Alkylpyridiniums react with nitroalkane and ethylmalonate anions by a radical nucleophilic substitution mechanism not involving radical chains.