A new method of bromination of aromatic rings by an iso-amyl nitrite/HBr system

Gavara, Laurent; Boisse, Thomas; Rigo, Benoı̂t; Hénichart, Jean‐Pierre

doi:10.1016/j.tet.2008.03.085

Cited by 30 publications

(14 citation statements)

References 33 publications

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“…[160][161][162] An alternative is to use an organic nitrite (isoamyl nitrite), with HBr acting as the bromine source. [163] In the above examples, the nitrogen compounds acting as stoichiometric oxidants generate a stoichiometric amount of nitrite salts or toxic nitrous oxides. To avoid this, ionic liquids with NO 3 À ions have been used as both an oxidant and a reaction medium for the chlorination and bromination of toluene, anisole, benzene, and naphthalene.…”

Section: Nitrogen Compounds As Catalysts For Aerobic Oxidative Halogementioning

confidence: 99%

Oxidative Halogenation with “Green” Oxidants: Oxygen and Hydrogen Peroxide

2009

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It is difficult to imagine organic chemistry without organo-halogen compounds and the molecular halogens needed for their preparation. The halogens have very different reactivity, with iodine usually requiring some form of activation, while others are reactive and hazardous chemicals. To avoid their use, various modified reagents have been discovered (N-bromo- and N-chlorosuccinimide, Selectfluor..), but halogens are used to prepare these reagents and when they are used the atom economy is poor. A better approach, which is based on biomimetric research on oxidative halogenation in nature, consists of generating the halogenating reagent in situ under acidic conditions from a halide salt. The result of such a reaction has been halogenation with 100 % halogen atom economy. Suitable oxidants for the oxidation of halides are hydrogen peroxide and oxygen.

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Section: Nitrogen Compounds As Catalysts For Aerobic Oxidative Halogementioning

confidence: 99%

Oxidative Halogenation with “Green” Oxidants: Oxygen and Hydrogen Peroxide

2009

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“…p-Bromotoluene+o-Bromotoluene ( 38b , 39b ). One mmol of substrate, 3 mmol IL-A, 1.1 mmol NBS, r.t. = 20 min, 55 °C; 1 H-NMR (CDCl 3 ): δ 7.55–7.49 (m, 1H), 7.36 (d, J = 8.3 Hz, 2H), 7.29–7.14 (m, 2H), 7.08–6.99 (m, 3H), 2.40 (s, 3H), 2.30 (s, 3H) [ 72 ].…”

Section: Methodsmentioning

confidence: 99%

Brønsted Acidic Ionic Liquid Accelerated Halogenation of Organic Compounds with N-Halosuccinimides (NXS)

Lü

You

et al. 2012

Molecules

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The Brønsted-acidic ionic liquid 1-methyl-3-(4-sulfobutyl)imidazolium triflate [BMIM(SO3H)][OTf] was demonstrated to act efficiently as solvent and catalyst for the halogenation of activated organic compounds with N-halosuccinimides (NXS) under mild conditions with short reaction times. Methyl aryl ketones were converted into α-halo and α,α-dihaloketones, depending on the quantity of NXS used. Ketones with activated aromatic rings were selectively halogenated, however in some cases mixtures of α-halogenated ketone and ring-halogenated ketones were obtained. Activated aromatics were regioselectively ring halogenated to give mono- and dihalo-substituted products. The [BMIM(SO3H)][OTf] ionic liquid (IL-A) was successfully reused eight times in a representative monohalogenation reaction with no noticeable decrease in efficiency. An effective halogenation scale-up in this IL is also presented. The reactivity trend and the observed chemo- and regioselectiivities point to an ET process in these IL-promoted halofunctionalization reactions.

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“…Bei 20 °C in wässriger TFA stellen sich die für diese Reaktion geeigneten Säurebedingungen ein 160–162. Alternativ kann auch ein organisches Nitrit (Isoamylnitrit) verwendet werden, wobei dann HBr als Bromquelle dient 163…”

Section: Aerobe Oxidative Halogenierungenunclassified

Oxidative Halogenierungen mit umweltschonenden Oxidationsmitteln: Sauerstoff und Wasserstoffperoxid

2009

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Eine organische Chemie ohne Organohalogenverbindungen und die zur Synthese benötigten molekularen Halogene ist schwer vorstellbar. Die Reaktivitäten der Halogene unterscheiden sich beträchtlich, und während Iod im Allgemeinen einer Aktivierung bedarf, sind die anderen Halogene äußerst reaktive und mithin auch gefährliche Chemikalien. Um den direkten Umgang mit Halogenen zu vermeiden, wurden diverse modifizierte Reagentien entwickelt (N‐Brom‐ und N‐Chlorsuccinimid, Selectfluor…︁), zu deren Herstellung aber wiederum Halogene verwendet werden und deren Anwendung stets mit einer schlechten Atomökonomie verbunden ist. Eine bessere Strategie, die auf der Grundlage biomimetischer Forschungen an natürlichen oxidativen Halogenierungen entworfen wurde, besteht darin, das Halogenierungsreagens in situ unter sauren Bedingungen aus Halogenidsalzen zu erzeugen. Das Ergebnis einer solchen Reaktion ist eine Halogenierung mit 100 % Halogenatomökonomie. Als Oxidationsmittel für die Oxidation des Halogenids bieten sich Wasserstoffperoxid und Sauerstoff an.

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A new method of bromination of aromatic rings by an iso-amyl nitrite/HBr system

Cited by 30 publications

References 33 publications

Oxidative Halogenation with “Green” Oxidants: Oxygen and Hydrogen Peroxide

Oxidative Halogenation with “Green” Oxidants: Oxygen and Hydrogen Peroxide

Brønsted Acidic Ionic Liquid Accelerated Halogenation of Organic Compounds with N-Halosuccinimides (NXS)

Oxidative Halogenierungen mit umweltschonenden Oxidationsmitteln: Sauerstoff und Wasserstoffperoxid

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