Electrochemical Reduction of 2,2-Dibromoacetophenone.

Batanero, Belén; Pastor, G.; Barba, Fructuoso; Díaz, José Manuel; Bassani, Silvina; Murase, Hiroki; Shono, Tatsuya; Toftlund, Hans

doi:10.3891/acta.chem.scand.53-0910

Cited by 11 publications

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“…2,2-Dibromo-1-arylethanones are used in organic synthesis primarily for the construction of heterocyclic structures [1][2][3] and small rings, [4][5][6] for the preparation of compounds with a double [7][8][9] or triple 10 bond, and in reactions with phosphorous esters 11,12 and thiols. 13,14 Most of the known methods for the synthesis of 2,2-dibromo-1arylethanones are based on bromination of acetophenones with molecular bromine 8,11,[15][16][17][18] and its complex compounds. 19,20 In the last two decades, chlorination and bromination of organic compounds with HCl or HBr combined with peroxides have developed extensively.…”

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confidence: 99%

A Convenient Synthesis of 2,2-Dibromo-1-arylethanones by Bromination of 1-Arylethanones with the H₂O₂-HBr System

Terent’ev¹,

Khodykin²,

Krylov³

et al. 2006

Synthesis

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S y n t h e s i s o f 2 , 2 -D i b r o m o -1 -a r y l e t h a n o n e s Alexander O. Terent'ev,* Abstract: 1-Arylethanones and related compounds are brominated in dioxane with the H 2 O 2 -HBr aq system, resulting in the replacement of two hydrogen atoms in the methyl group with bromine. The reaction is also accompanied by bromination of the aromatic ring provided that the latter contains electron-donating substituents. The reaction proceeds rapidly (20 min) and results in complete conversion of ketones to give 2,2-dibromo-1-arylethanones in yields up to 86%.2,2-Dibromo-1-arylethanones are used in organic synthesis primarily for the construction of heterocyclic structures 1-3 and small rings, 4-6 for the preparation of compounds with a double 7-9 or triple 10 bond, and in reactions with phosphorous esters 11,12 and thiols. 13,14 Most of the known methods for the synthesis of 2,2-dibromo-1-arylethanones are based on bromination of acetophenones with molecular bromine 8,11,15-18 and its complex compounds. 19,20 In the last two decades, chlorination and bromination of organic compounds with HCl or HBr combined with peroxides have developed extensively. 21-38 These methods are most actively used for halogenation of arenes, 22-26,28-36 alkenes, 21,23 and ketones. 37,38 As part of our continuing studies on the use of hydrogen peroxide in organic synthesis, in particular the halogenation of ketones, 38 we report the results of bromination of 1-arylethanones with the H 2 O 2 -HBr system. The influence of experimental conditions on the selectivity of bromination and the yield of 2,2-dibromo-1-phenylethanone was revealed using acetophenone (1) as an example (Scheme 1, Table 1). The reaction was carried out by adding 35% aqueous hydrogen peroxide to a refluxing solution of ketone 1 in dioxane (acetic acid) and 48% hydrobromic acid for one minute. Then the mixture was refluxed with stirring for 20 minutes. The reaction afforded dibromoketone 3 as the major product and mono-(2) and tribromoketones (4) as by-products.Our study demonstrated that the highest yield (84%) of dibromoketone 3 was achieved in the presence of a fourfold molar excess of H 2 O 2 (run 1). In the presence of a threefold molar excess of H 2 O 2 (run 2), the yield of 3 decreased to 78%, and monobromoketone 2 remained unconsumed. A decrease in the amount of HBr (run 3), a decrease in the reaction time to 8 min (run 4), or lowering of the reaction temperature to 50 °C (run 5) also lead to a decrease in the yield of dibromoketone 3.Bromination of ketone 1 in acetic acid in the presence of sulfuric acid afforded dibromoketone 3 in 43% yield and tribromoketone 4 in 48% yield. The formation of product 4 is the first example of the preparation of 2,2,2-tribromo-1-phenylethanone in an acidic medium in a satisfactory yield. The use of a larger amount of H 2 O 2 did not lead to a considerable increase in the conversion of acetophenone 1 to tribromoketone 4. Alternative procedures for the synthesis of tribromoketone 4 are based on bromination of acetophenone in ac...

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confidence: 99%

A Convenient Synthesis of 2,2-Dibromo-1-arylethanones by Bromination of 1-Arylethanones with the H₂O₂-HBr System

Terent’ev¹,

Khodykin²,

Krylov³

et al. 2006

Synthesis

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“…In all cases a low concentration of phenacyl halide could be convenient to avoid the further attack of the initially formed brominated phenacyl anion to a new molecule of 2 , as it was already described to produce undesired halogenated ketoepoxides . However, in the presence of 1,4-quinone molecules the ketoepoxide was never detected.…”

Section: Results and Discusionmentioning

confidence: 89%

“…This mechanism proposal is supported by the trace formation of 1,2,3-tri-(4-chloro-benzoyl)cyclopropane MS-GC (CI, m / z (relative intensity): 497 (M + +41, 0.1), 485 (M + +29, 2), 459 (M + +3, 9.4), 457 (M + +1, 9.1) and 1,4-diphenyl-but-2-ene-1,4-dione as side product, detected in MS-GC (EI, m / z (relative intensity): 236 (M + , 62), 208 (M + -CO, 31), 179(3), 159(3), 131(9), 105(100), 77(91), 51(42). This compound should be formed via carbene, as indicated in Scheme , because the phenacyl anions (brominated or not) behave, as already described, , through addition processes (not substitution) with regard to another phenacyl halide molecule.…”

Section: Results and Discusionmentioning

confidence: 92%

Stereoselective Cyclopropanation to Homoquinones from Phenacyl Carbenes Obtained through Quinone-Electrogenerated Bases

et al. 2017

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A series of new (E) and (Z)-benzoyl-homoquinones have been prepared in good yield by the parent quinone-electrogenerated base (EGB) in the presence of α-bromoacetophenones or α-bromopropiophenone. The EGB, obtained when electrolysis of p-benzoquinone, or 1,4-naphthoquinone, is carried out at the reduction potential of their first voltammetric peak, conducted to electrogenerated phenacyl carbenes after halide evolution on the first obtained bromo-enolates. The stereoselectivity of the [2 + 2]cycloaddition of the carbene to the quinoid substrate is highly dependent on the electrode nature. Reaction mechanism proposal is discussed.

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“…In 1999, Barba et al., reported an electrochemical debrominative reduction of 2,2‐dibromoacetophenone 1 a , which was converted to trimerized cyclopropane 150 via in situ generated ketocarbenoid 1 a′ in a cathodic reduction (Scheme ). On the other hand, dimeric oxirane derivative 151 was also obtained when the reaction was carried out in DMF solvent under aprotic medium.…”

Section: αα‐Dihaloketones As Building Blocks In Organic Synthesismentioning

confidence: 99%

The α,α‐Dihalocarbonyl Building Blocks: An Avenue for New Reaction Development in Organic Synthesis

Sadhukhan

Santhi

Baire

2020

Chemistry A European J

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The α,α‐dihalocarbonyl moiety is a bifunctional system with a gem‐dihalocarbon and a carbonyl carbon in 1,2‐fashion. This is one of the privileged scaffolds in medicinal chemistry due to its chemical and metabolic stability and lipophilicity. They have also been found in numerous structurally divergent natural products and most of their fabricated structures have already been in medicinal use. Apart from their important use in medicinal chemistry, the α,α‐dihalocarbonyl groups have been employed as key building blocks for the development of novel synthetic strategies and utilized as intermediates in total synthesis. In addition to the traditional transformations such as oxidations, reductions, and C−C bond formations, recently several new and non‐classical reactions have also been developed. This review provides short description of existing methods for their synthesis and detailed discussion on the efforts for the discovery and development of new reactions by employing α,α‐dihaloketones as synthetic building blocks. We have presented their use as key functional groups for the synthesis of polycyclic systems of medicinal and material importance and natural products.

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Electrochemical Reduction of 2,2-Dibromoacetophenone.

Cited by 11 publications

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A Convenient Synthesis of 2,2-Dibromo-1-arylethanones by Bromination of 1-Arylethanones with the H₂O₂-HBr System

A Convenient Synthesis of 2,2-Dibromo-1-arylethanones by Bromination of 1-Arylethanones with the H₂O₂-HBr System

Stereoselective Cyclopropanation to Homoquinones from Phenacyl Carbenes Obtained through Quinone-Electrogenerated Bases

The α,α‐Dihalocarbonyl Building Blocks: An Avenue for New Reaction Development in Organic Synthesis

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Electrochemical Reduction of 2,2-Dibromoacetophenone.

Cited by 11 publications

References 0 publications

A Convenient Synthesis of 2,2-Dibromo-1-arylethanones by Bromination of 1-Arylethanones with the H2O2-HBr System

A Convenient Synthesis of 2,2-Dibromo-1-arylethanones by Bromination of 1-Arylethanones with the H2O2-HBr System

Stereoselective Cyclopropanation to Homoquinones from Phenacyl Carbenes Obtained through Quinone-Electrogenerated Bases

The α,α‐Dihalocarbonyl Building Blocks: An Avenue for New Reaction Development in Organic Synthesis

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A Convenient Synthesis of 2,2-Dibromo-1-arylethanones by Bromination of 1-Arylethanones with the H₂O₂-HBr System

A Convenient Synthesis of 2,2-Dibromo-1-arylethanones by Bromination of 1-Arylethanones with the H₂O₂-HBr System