Reactions of organic anions, 182. Vicarious nucleophilic substitution of a hydrogen atom in 1‐fluoro‐2,4‐dinitrobenzene (Sanger's Reagent)

Mąkosza, Mieczysław; Stalewski, Jacek

doi:10.1002/jlac.1991199101112

Cited by 14 publications

(8 citation statements)

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“…-dinitrofluorobenzene, the Sanger reagent, known for very fast replacement of fluorine with nucleophiles, reacts with a-halocarbanions along the VNS of hydrogen pathway (Scheme 8). 25 The VNS products stay in the reaction mixture in the form of nitrobenzylic carbanions that are no longer electrophilic, thus the reaction proceeds selectively as a monosubstitution. However, in the case of m-dinitrobenzenes, the anionic products have nitrocyclohexadiene structures that are related to Michael acceptors, so they can add a second carbanion and afford disubstitution products.…”

Section: Vicarious Nucleophilic Substitution Of Hydrogen (Vns)mentioning

confidence: 99%

Nucleophilic Substitution of Hydrogen in Nitroarenes: A New Chapter of Aromatic Chemistry

Mąkosza¹

2011

Synthesis

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Basic concepts, mechanistic principles and the broad application of nucleophilic substitution of hydrogen in nitroarenes and other electron-deficient arenes in organic synthesis are presented in a concise way. It was shown that the initial process between nucleophiles and (halo)nitroarenes is a fast and reversible addition-in positions occupied by hydrogen-to form anionic s H adducts that can then be converted into products of nucleophilic substitution of hydrogen in a few ways. Only when these pathways for rapid conversion of the s H adducts into products of nucleophilic substitution of hydrogen are not available, do the s H adducts dissociate. The subsequent slower formation of s X adducts, followed by departure of X anions, results in the conventional nucleophilic aromatic substitution of halogens, namely the S N Ar reaction. Thus the S N Ar reaction is a secondary ipso substitution, whereas nucleophilic substitution of hydrogen is a primary fast process. It is therefore necessary to introduce corrections in appropriate chapters of textbooks and monographs.

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Section: Vicarious Nucleophilic Substitution Of Hydrogen (Vns)mentioning

confidence: 99%

Nucleophilic Substitution of Hydrogen in Nitroarenes: A New Chapter of Aromatic Chemistry

Mąkosza¹

2011

Synthesis

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“…The product from the reaction was potassium 4-methoxycarbomethyl-5-nitro-2-pyridinesulfonate (10), obtained in 43% yield from a VNS reaction in the 4-position. This outcome is in accordance with the results reported by Makosza et al, the VNS reaction is usually faster than a competing S N Ar reaction.…”

Section: Discussionmentioning

confidence: 99%

“…This outcome is in accordance with the results reported by Makosza et al, the VNS reaction is usually faster than a competing S N Ar reaction. 10 Compound 10 contains the para relationship between the sulfonate group and the nitro group. The sulfonate group might therefore be substituted by suitable nucleophiles by analogy with the reac-…”

Section: Discussionmentioning

confidence: 99%

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Nucleophilic alkylations of 3-nitropyridines

et al. 2004

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3-Nitropyridine and 4-substituted-3-nitropyridines were reacted with chloroform, methyl chloroacetate and ethyl 2-chloropropionate under vicarious nucleophilic substitution (VNS) conditions. Substitution was obtained in the ortho or para position to the nitro group with acceptable to good yields and regioselectivity. With potassium 5-nitropyridine-2-sulfonate the substitution took place in the 4-position. Further substitution of the sulfonate group proved to be possible.

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“…To show strong preference for nucleophilic substitution of a hydrogen atom over conventional substitution of a halogen atom, it should be mentioned that α‐halocarbanions react with 2,4‐dinitrofluorobenzene, the Sanger reagent, exclusively according to the VNS pathway; substitution of a fluorine atom by using these carbanions is not observed when the reaction is carried out at low temperature in the presence of an excess of base (Scheme ) 22…”

Section: Nucleophilic Substitution Of Hydrogen Atoms Snarhmentioning

confidence: 99%

Reactions of Nucleophiles with Nitroarenes: Multifacial and Versatile Electrophiles

Mąkosza

2014

Chemistry A European J

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In this overview, it is shown that there are many initial reactions between nitroarenes and nucleophiles: addition to the electron-deficient ring at positions occupied by halogen and hydrogen atoms, addition to the nitro group, single-electron transfer (SET), and other types of initial reactions. The resulting intermediates react further in a variety of ways to form products of nucleophilic substitution of a halogen atom (SN Ar), a hydrogen atom (SN ArH), and others. Many variants of these processes are briefly discussed, particularly in relation of rates of the initial reactions and further transformations.

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Reactions of organic anions, 182. Vicarious nucleophilic substitution of a hydrogen atom in 1‐fluoro‐2,4‐dinitrobenzene (Sanger's Reagent)

Cited by 14 publications

References 9 publications

Nucleophilic Substitution of Hydrogen in Nitroarenes: A New Chapter of Aromatic Chemistry

Nucleophilic Substitution of Hydrogen in Nitroarenes: A New Chapter of Aromatic Chemistry

Nucleophilic alkylations of 3-nitropyridines

Reactions of Nucleophiles with Nitroarenes: Multifacial and Versatile Electrophiles

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