Synthesis of Brominated Imidazoles.

Stensiö, Karl-Erland; Wahlberg, Kerstin; Wahren, Robert; Waisvisz, Jacques M.; Hoeven, Marcel G. van der; Swahn, Carl‐Gunnar

doi:10.3891/acta.chem.scand.27-2179

Cited by 42 publications

(24 citation statements)

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“…2.1 Synthesis of 4,5-dibromoimidazole 4,5-dibromoimidazole was synthesized by following the procedure by Stensio et al [23] with some modification. Imidazole (1.36 g) was added to a solution of sodium acetate (20 g) in acetic acid (180 ml) and stirred for 10 minutes to dissolve.…”

Section: Methodsmentioning

confidence: 99%

Enhancement of the Bioactivity of 4, 5-dibromoimidazole by its Cobalt (II) Complex

I.A¹,

R.I²,

C.E³

2014

IOSRJAC

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Section: Methodsmentioning

confidence: 99%

Enhancement of the Bioactivity of 4, 5-dibromoimidazole by its Cobalt (II) Complex

I.A¹,

R.I²,

C.E³

2014

IOSRJAC

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“…Imidazole 19, which is sensitive to usual bromination (31), was brominated to 2,4,5-tribromoimidazole 19a in high yield. This product is believed to be capable of catalytically reactivating phosphorylated acetylcholinesterase (38). In yet another interesting reaction, bisphenol-A 20 was brominated to tetrabromobisphenol-A (4,4?-isopropylidenebis-(2,6-dibromophenol)) 20a under the conditions used herein.…”

Section: Screening Of Reaction Conditionsmentioning

confidence: 97%

Boric acid catalyzed bromination of a variety of organic substrates: an eco-friendly and practical protocol

Nath

Chaudhuri

2008

Green Chemistry Letters and Reviews

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An environmentally benign, easy to operate, and practical protocol for the regioselective bromination of aromatic compounds using boric acid as a recyclable catalyst, KBr as the source of bromide and hydrogen peroxide as the oxidant is described. Peroxoborate generated in solution, from the reaction of boric acid and H 2 O 2 , very effectively catalyses the bromination of organic substrates at room temperature in a selective manner. The catalyst used is inexpensive, eco-friendly, safe to handle, and recyclable. The methodology is chemoselective for dibenzylidineacetone and regioselective for the other substrates. High yields of the products, mild reaction conditions, high selectivity, use of H 2 O or C 2 H 5 OH as solvent, and redundancy of bromine are some of the major advantages of the synthetic protocol.Keywords: arenes; aryl ketone; alkenes; bromination; hydrogen peroxide; boric acid IntroductionOwing to their increasing commercial use, brominated aromatic compounds are very important in synthetic organic chemistry. They are key intermediates in the preparation of many organometallic reagents (1Á4) and play vital roles in transition metal mediated coupling reactions such as Stille (5), Suzuki (6), Heck (7,8), and Sonogashira reactions (9,10). Many pesticides, insecticides, herbicides, pharmaceutically and medicinally active molecules, and fire retardants carry bromo functionality (11).The need for isomerically pure bromoaromatic compounds has led to develop selective brominating agents or bromination protocols (12). Most of the processes currently practiced for the bromination of aryl compounds employ toxic, corrosive, and rather expensive molecular bromine, resulting in the formation of large amount of HBr waste, thereby reducing the atom efficiency by 50% (11). In large scale operations this causes environmental problems in addition to being expensive. Bromination using HBr with either H 2 O 2 (11,13Á15) or O 2 (16Á18) as an oxidant was thought to be a possible solution. This, however, met with partial success. In addition, HBr is highly toxic and corrosive, and is as harmful as molecular bromine. These problems enhanced the appeal of bromination protocols based on oxidation of bromide salt by H 2 O 2 with better bromide atom economy (13Á16,19,20). The systems reported so far require metal or other catalysts and volatile organic solvents (16,19,21Á24 ( as the active brominating agent, and finally (iii), site-selective bromination of organic substrates to afford bromoorganic compounds (Scheme 1).Our earlier work on peroxoborate (29) and oxidative bromination of aromatics (30) suggested that the peroxoborate intermediate generated in situ would enable bromide oxidation in presence of an acid. The fact, that Br 3 is formed in this process has been ascertained from an independent experiment wherein Br was oxidized by the present methodology in the absence of any organic substrate but in the presence of tetrabutylammonium chloride and three equivalents of KBr leading to nearly quantitative isolation of tetrabut...

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“…Bromination of imidazole, first described in 1877 [1], gives 2,4,5-tribromoimidazole [2,3]; the fully brominated derivative is also obtained from 1-methylimidazole [4,5]. Different brominating agents and systems are known to effect this transformation [6 -9].…”

Section: Introductionmentioning

confidence: 99%

“…Different brominating agents and systems are known to effect this transformation [6 -9]. Dibromo and monobromo compounds have been obtained by selective reduction of tribromo compounds using sodium sulfite [2,3] or butyllithium [3]. Removal of the most reactive bromine atom in position 2 by a Grignard reagent gave 4,5-dibromo-1-methylimidazole in good yield [5].…”

Section: Introductionmentioning

confidence: 99%

Bromination of 1-Hydroxyimidazoles. Synthesis and Crystal Structures

Laus

Wurs

Kahlenberg

et al. 2012

Zeitschrift Für Naturforschung B

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Bromination of 1-hydroxyimidazole 3-oxide and 1-hydroxy-2-methylimidazole 3-oxide using bromine in acetic acid gave 2-bromo-1,3-dihydroxyimidazole hydrobromide and 4,5-dibromo-1,3-dihydroxy-2-methylimidazole hydrobromide, respectively. In contrast, bromination in aqueous mixture (acetic acid, methanol, dimethylformamide, tetrahydrofuran) yielded 2,4,5-tribromo-1-hydroxyimidazole. Crystal structures of four compounds were determined by X-ray diffraction.

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Synthesis of Brominated Imidazoles.

Cited by 42 publications

References 0 publications

Enhancement of the Bioactivity of 4, 5-dibromoimidazole by its Cobalt (II) Complex

Enhancement of the Bioactivity of 4, 5-dibromoimidazole by its Cobalt (II) Complex

Boric acid catalyzed bromination of a variety of organic substrates: an eco-friendly and practical protocol

Bromination of 1-Hydroxyimidazoles. Synthesis and Crystal Structures

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