Sodium Salts (NaI/NaBr/NaCl) for the Halogenation of Imidazo-Fused Heterocycles

Semwal, Rashmi; Ravi, Chitrakar; Kumar, Rahul; Meena, Ramavatar; Adimurthy, Subbarayappa

doi:10.1021/acs.joc.8b02637

Cited by 105 publications

(37 citation statements)

References 55 publications

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“…Another option is to use Br 2 , but to minimize the hazards by producing it in situ, by reacting reduced bromide (in the form of hydrobromic acid or a bromide salt) with an oxidizing agent, e.g., hydrogen peroxide and other peroxides [16,17,18], Oxone [19], bromate [20,21], or even air or oxygen at elevated temperatures or with a catalyst [22]. This approach solves the storage and transport problem, but the risk of a runaway reaction is still present.…”

Section: Introductionmentioning

confidence: 99%

Electrophilic Bromination in Flow: A Safe and Sustainable Alternative to the Use of Molecular Bromine in Batch

et al. 2019

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Bromination reactions are crucial in today’s chemical industry since the versatility of the formed organobromides makes them suitable building blocks for numerous syntheses. However, the use of the toxic and highly reactive molecular bromine (Br2) makes these brominations very challenging and hazardous. We describe here a safe and straightforward protocol for bromination in continuous flow. The hazardous Br2 or KOBr is generated in situ by reacting an oxidant (NaOCl) with HBr or KBr, respectively, which is directly coupled to the bromination reaction and a quench of residual bromine. This protocol was demonstrated by polybrominating both alkenes and aromatic substrates in a wide variety of solvents, with yields ranging from 78% to 99%. The protocol can easily be adapted for the bromination of other substrates in an academic and industrial environment.

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Section: Introductionmentioning

confidence: 99%

Electrophilic Bromination in Flow: A Safe and Sustainable Alternative to the Use of Molecular Bromine in Batch

et al. 2019

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“…Benzyl alcohol 1a is an important precursor for organic synthesis and a useful solvent because of its polarity, low toxicity, mildly pleasant aromatic odor, and low vapor pressure [52][53][54]. e chemoselective oxidation property of compound 1a was also very useful in functional transformations for the preparation of aldehydes [55,56] and their dicarboxyl analogues [57,58]. For these reasons, we carried out a plausible oxidation of benzyl alcohol 1a.…”

Section: Resultsmentioning

confidence: 99%

Cyclopentadienyl Ruthenium(II) Complex-Mediated Oxidation of Benzylic and Allylic Alcohols to Corresponding Aldehydes

Tseng

Hsiao

Wong

et al. 2019

Heteroatom Chemistry

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This work reports an efficient method for the oxidation reaction of aliphatic, aromatic allylic, and benzylic alcohols into aldehydes catalyzed by the cyclopentadienyl ruthenium(II) complex (RuCpCl(PPh3)2) with bubbled O2. Through further optimizing controlled studies, the tendency order of oxidation reactivity was determined as follows: benzylic alcohols > aromatic allylic alcohols >> aliphatic alcohols. In addition, this method has several advantages, including a small amount of catalyst (0.5 mol%) and selective application of high discrimination activity of aliphatic, aromatic allylic, and benzylic alcohols.

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“…Adimurthy [93] and Katrun [94] groups independently reported a K 2 S 2 O 8 -mediated halogenation of imidazo-[1,2-a]pyridines 1 using readily available NaI/NaBr/ NaCl as halogen sources by varying different solvents such as CH 3 CN, DCM and mixture of CH 3 CN/H 2 O) for each halogenation reaction as described in Scheme 62. Various imidazoheterocycles (1-3) reacted with NaX (X = Cl, Br, I) smoothly and produced corresponding 3-haloimidazo[1,2-a]pyridines 91/93 in 31-96% yields.…”

Section: C-halogen Bond Formationmentioning

confidence: 99%

Recent Advances in Radical C−H Bond Functionalization of Imidazoheterocycles

et al. 2020

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Direct CÀ H bond functionalization through radical pathway has emerged as a powerful and ideal strategy for the synthesis of organic compounds. This review provides an overview of recent developments in radical CÀ H functionalization of imidazoheterocycles such as imidazo[1,2-a] pyridine, benzo[d]imidazo[2,1-b]thiazole, imidazo [2,1-b]thiazole, imidazo[1,2-a]pyrimidine, imidazo [2,1-a]isoquinoline, imidazo[1,2-a]pyrazine and imidazo[1,2-a]quinoline using organic peroxides, photo/electric-induced protocols, iodine-based reagents, first-row transition metal catalysts (Fe, Mn, Ni and Cu) and inorganic oxidants/or

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Sodium Salts (NaI/NaBr/NaCl) for the Halogenation of Imidazo-Fused Heterocycles

Cited by 105 publications

References 55 publications

Electrophilic Bromination in Flow: A Safe and Sustainable Alternative to the Use of Molecular Bromine in Batch

Electrophilic Bromination in Flow: A Safe and Sustainable Alternative to the Use of Molecular Bromine in Batch

Cyclopentadienyl Ruthenium(II) Complex-Mediated Oxidation of Benzylic and Allylic Alcohols to Corresponding Aldehydes

Recent Advances in Radical C−H Bond Functionalization of Imidazoheterocycles

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