- Catalyst-Free 1,2-Dibromination of Alkenes Using 1,3-Dibromo-5,5-dimethylhydantoin (DBDMH) as a Bromine Source
-
A direct 1,2-dibromination method of alkenes is realized using 1,3-dibromo-5,5-dimethylhydantoin (DBDMH) as a bromine source. This reaction proceeds under mild reaction conditions without the use of a catalyst and an external oxidant. Various sorts of alkene substrates are transformed into the corresponding 1,2-dibrominated products in good to excellent yields with broad substrate scope and exclusive diastereoselectivity. This method offers a green and practical approach to synthesize vicinal dibromide compounds.
- Wang, Lei,Zhai, Lele,Chen, Jinyan,Gong, Yulin,Wang, Peng,Li, Huilin,She, Xuegong
-
supporting information
p. 3177 - 3183
(2022/02/23)
-
- Dibrominated addition and substitution of alkenes catalyzed by Mn2(CO)10
-
A practical method for the dibromination of alkenes without using molecular bromine is consistently appealing in organic synthesis. Herein, we report Mn-catalyzed dibrominated addition and substitution of alkenes only with N-bromosuccinimide, producing a variety of synthetically valuable dibrominated compounds in moderate to high yields. This journal is
- Chan, Albert S. C.,Jiang, Yi,Meng, Shanshui,Song, Xianheng,Zhang, Hong,Zou, Yong
-
supporting information
p. 13385 - 13388
(2021/12/17)
-
- A General Method for the Dibromination of Vicinal sp3C-H Bonds Exploiting Weak Solvent-Substrate Noncovalent Interactions
-
A general procedure of 1,2-dibromination of vicinal sp3 C-H bonds of arylethanes using N-bromosuccinimide as the bromide reagent without an external initiator has been established. The modulation of the strength of the intermolecular noncovalent interactions between the solvent and arylethane ethanes, quantitatively evaluated via quantum chemical calculations, allows us to circumvent the fact that arylethane ethane cannot be dibrominated through traditional methods. The mechanism was explored by both experiments and quantum chemical calculations, revealing a radical chain with HAA process.
- Qi, Zaojuan,Li, Weihe,Niu, Yanning,Benassi, Enrico,Qian, Bo
-
supporting information
p. 2399 - 2404
(2021/03/03)
-
- One-pot and regioselective synthesis of functionalized γ-lactams via a metal-free sequential Ugi 4CR/Intramolecular 5-exo-dig cyclization reaction
-
A new one-pot and regioselective synthesis of functionalized γ-lactams by a metal-free Ugi 4CR/intramolecular 5-exo-dig cyclization sequence under mild conditions has been developed. The reaction of propenoic acids, aldehydes, amines, and isocyanides produced γ-lactams regioselectively in 72–89percent yields via sequential Ugi 4CR/intramolecular 5-exo-dig cyclization reaction in the presence of Cs2CO3.
- Yan, Yan-Mei,Wang, Meng-Liang,Liu, Yu-Long,He, Ying-Chun
-
-
- Preparation method of 1-aryl-1,2-dibromoethane
-
The invention relates to a preparation method of 1-aryl-1,2-dibromoethane. The preparation method of 1-aryl-1,2-dibromoethane includes the steps: under a nitrogen atmosphere, a solvent, an aryl alkaneand N-bromosuccinimide are added in to a reaction tube in sequence, a dibromination reaction is conducted at 80-120 DEG C for 12-48 hours, then, the dibromination reaction is finished, the solvent isremoved through evaporation, and through column chromatography separation, 1-aryl-1,2-dibromoethane compounds are obtained. According to the preparation method of 1-aryl-1,2-dibromoethane, a synthesis technology is simple, reaction conditions are mild, the yield of 1-aryl-1,2-dibromoethane is high, and thus the preparation method of 1-aryl-1,2-dibromoethane is easy to industrialize.
- -
-
Paragraph 0022-0023
(2020/03/16)
-
- Enantiospecific on-water bromination: A mild and efficient protocol for the preparation of alkyl bromides
-
Herein we report the first example of an on-water enantiospecific synthesis of alkyl bromides. This procedure allowed the conversion of secondary activated alkyl sulphides to benzylic alkyl bromides, which were obtained in 80-99% yields. The reaction carried out on enantio-pure sulphides provided the corresponding bromides in high yields and enantioselectivity (up to 92% ee; 94% es) at room temperature. The on-water conditions reduced significantly the reaction times compared to similar procedures run in organic media. The condition identified made use of no solvent, required no temperature control and produced a smooth organic phase easily separated for further synthetic use on a multigram-scale without the need for any organic extraction. Therefore, the present constitutes the most operationally simple and environmentally benign approach to a class of much sought organic intermediates. This journal is
- Alletto, Francesco,Adamo, Mauro F. A.
-
supporting information
p. 8692 - 8698
(2020/12/29)
-
- Synthesis and antibacterial evaluation of novel 11-O-aralkylcarbamoyl-3-O-descladinosylclarithromycin derivatives
-
A series of novel 11-O-aralkylcarbamoyl-3-O-descladinosylclarithromycin derivatives were designed, synthesized and evaluated for their in vitro antibacterial activity. The results showed that the majority of the target compounds displayed potent activity against erythromycin-susceptible S. pyogenes, erythromycin-resistant S. pneumoniae A22072 expressing the mef gene and S. pneumoniae AB11 expressing the mef and erm genes. Besides, most of the target compounds exhibited moderate activity against erythromycin-susceptible S. aureus ATCC25923 and B. subtilis ATCC9372. In particular, compounds 11a, 11b, 11c, 11e, 11f and 11h were found to exert favorable antibacterial activity against erythromycin-susceptible S. pyogenes with the MIC values of 0.015–0.125 μg/mL. Furthermore, compounds 10e, 11a, 11b and 11c showed superior activity against erythromycin-resistant S. pneumoniae A22072 with the MIC values of 0.25–0.5 μg/mL. Additionally, compound 11c was the most effective against all the erythromycin-resistant S. pneumoniae strains (A22072, B1 and AB11), exhibiting 8-, 8- and 32-fold more potent activity than clarithromycin, respectively.
- Jia, Li,Wang, Yinhu,Wang, Yanxia,Qin, Yinhui,Hu, Chaoyu,Sheng, Juzheng,Ma, Shutao
-
supporting information
p. 2471 - 2476
(2018/06/06)
-
- Method for synthesizing alpha,beta-dibromide
-
The invention discloses a method for synthesizing alpha,beta-dibromide. The method is characterized in that a styrene compound as shown in the formula I is taken as a raw material, Zn-Al hydrotalciteZnAl-BrO3-LDHs of a bromate intercalation is taken as
- -
-
Paragraph 0048; 0049; 0050
(2018/04/01)
-
- Dibromination of alkenes with LiBr and H2O2 under mild conditions
-
Electron-rich and electron-poor alkenes, and alkenes bearing protecting groups can be efficiently and stereoselectively converted to trans-dibromides using LiBr/H2O2 and AcOH as a proton source in 1,4-dioxane. For most substrates addition of 0.1 mol% of PhTeTePh enhances the reaction rate and the yield of the products. Experimental data suggest that the brominating agent prepared in situ is molecular bromine and that LiBr assists the activation of H2O2 allowing bromination to occur using AcOH as a mild proton source in uncatalyzed experiments. Scale-up is feasible: 10.0 mmol of 1-octene was quantitatively converted to 1,2-dibromooctene in one hour of reaction at room temperature.
- Martins, Nayara Silva,Alberto, Eduardo E.
-
supporting information
p. 161 - 167
(2017/12/28)
-
- PPh3O as an Activating Reagent for One-Pot Stereoselective Syntheses of Di- and Polybrominated Esters from Simple Aldehydes
-
(Chemical Equation Presented) An efficient one-pot method for the syntheses of di- and polybrominated esters from readily available aldehydes is reported. The direct use of the in situ generated byproduct PPh3O in the following reactions greatly improves the efficiency of the cascade. Also, the substrate scope of the reaction is proved to be broad.
- Yu, Tian-Yang,Wei, Hao,Luo, Yong-Chun,Wang, Yao,Wang, Zhu-Yin,Xu, Peng-Fei
-
p. 2730 - 2736
(2016/04/26)
-
- Synthesis and biological evaluation of a series of benzoxazole/ benzothiazole-containing 2,3-dihydrobenzo[b][1,4]dioxine derivatives as potential antidepressants
-
A series of benzoxazole/benzothiazole-2,3-dihydrobenzo[b][1,4]dioxine derivatives (5a-5d and 8a-8j) was synthesized. Compounds were evaluated for binding affinities at the 5-HT1A and 5-HT2A receptors. Antidepressant activities of the compounds were screened using the forced swimming test (FST) and the tail suspension test (TST). The results indicated that the compounds exhibited high affinities for the 5-HT1A and 5-HT2A receptors and showed a marked antidepressant-like activity. Compound 8g exhibited high affinities for the 5-HT1A (Ki = 17 nM) and 5-HT2A (Ki = 0.71 nM) receptors; it also produced a decrease of the immobility time and exhibited potent antidepressant-like effects in the FST and TST in mice.
- Wang, Songlin,Chen, Yin,Zhao, Song,Xu, Xiangqing,Liu, Xin,Liu, Bi-Feng,Zhang, Guisen
-
p. 1766 - 1770
(2014/04/17)
-
- Brominations with Pr4NBr9 as a solid reagent with high reactivity and selectivity
-
Tetrapropylammonium nonabromide (Pr4NBr9) is introduced as a room-temperature solid reagent for rapid bromination reactions of various substrates. The reagent exhibits reactivity similar to that of elemental bromine, but shows higher selectivity and it is easier and safer to store and to handle. Georg Thieme Verlag Stuttgart · New York.
- Beck, Thorsten M.,Haller, Heike,Streuff, Jan,Riedel, Sebastian
-
p. 740 - 747
(2014/04/03)
-
- Triphenylphosphine oxide-catalyzed stereoselective poly- and dibromination of unsaturated compounds
-
A novel PPh3O catalyzed bromophosphonium salt-mediated dibromination of α,β-unsaturated esters and β,γ- unsaturated α-ketoesters has been developed. The products were obtained with good to excellent yields and excellent diastereoselectivities.
- Yu, Tian-Yang,Wang, Yao,Hu, Xiu-Qin,Xu, Peng-Fei
-
supporting information
p. 7817 - 7820
(2014/07/08)
-
- Aqueous Et4NBrO3/KBr as a versatile and environmentally benign source of bromine for the selective trans-bromination of alkenes
-
An aqueous solution of tetraethyl ammonium bromate and potassium bromide is found to be an environmentally benign source of bromine at ambient temperature. This reagent is used for selective trans-dibromination of several substituted alkenes. The reaction conditions are mild and the yield of the products are high and other possible by-products such as bromohydrin formation and aromatic substitution have not been observed.
- Das, Pranab Jyoti,Sarkar, Sudeshna
-
p. 802 - 806
(2013/07/26)
-
- Alkoxybromination of olefins using ammonium bromide and oxone
-
A mild, efficient, and highly regio- and stereoselective method for the methoxy and ethoxy bromination of olefins has been developed using NH 4Br as a bromine source and Oxone as an oxidant. Various kinds of olefins (aromatic, linear, and cyclic olefins) afforded the corresponding alkoxy brominated products in moderate to excellent yields. Taylor & Francis Group, LLC.
- Kumar, Macharla Arun,Naresh, Mameda,Rohitha, Chozhiyath Nappunni,Narender, Nama
-
supporting information
p. 3121 - 3129
(2014/01/06)
-
- Regio-and stereoselective hydroxybromination and dibromination of olefins using ammonium bromide and oxone
-
An efficient protocol for the synthesis of vicinal bromohydrins and dibromides from olefins is presented. Various olefins are regio-and stereoselectively hydroxybrominated and dibrominated with anti fashion, following Markonikov's rule, using eco-friendly, non-toxic, and stable reagents such as NH4Br and oxone in CH3CN/H2O (1:1) and CH3CN without employing catalyst in moderate to excellent yields. Bromohydrins are formed instantaneously.
- MacHarla, Arun Kumar,Chozhiyath Nappunni, Rohitha,Nama, Narender
-
supporting information; experimental part
p. 1401 - 1405
(2012/04/04)
-
- Ru-catalyzed highly chemo- and enantioselective hydrogenation of γ-halo-γ,δ-unsaturated-β-keto esters under neutral conditions
-
Finely-tuned ruthenium-catalyzed highly chemoselective and enantioselective hydrogenation of γ-halo-γ,δ-unsaturated-β-keto esters at the carbonyl group was achieved under neutral reaction conditions (ee up to 97%). Both olefin and alkenyl halogen moieties, which are labile under hydrogenation conditions, remained untouched during the reaction.
- Ma, Xin,Li, Wanfang,Li, Xiaoming,Tao, Xiaoming,Fan, Weizheng,Xie, Xiaomin,Ayad, Tahar,Ratovelomanana-Vidal, Virginie,Zhang, Zhaoguo
-
supporting information; experimental part
p. 5352 - 5354
(2012/06/30)
-
- Organocatalysis as a safe practical method for the stereospecific dibromination of unsaturated compounds
-
Organocatalytic stereospecific dibromination of a wide variety of functionalized alkenes was achieved using a stable, inexpensive halogen source, 1,3-dibromo 5,5-dimethylhydantoin, and a simple thiourea catalyst at room temperature. The presence of a tertiary amine enhanced the rate of the dibromination reaction, and yields were good in various solvents, including aqueous solvents. The procedure was extended to alkynes and aromatic rings and to dichlorination reactions by using the 1,3-dichloro hydantoin derivative.
- Hernandez-Torres, Gloria,Tan, Bin,Barbas, Carlos F.
-
supporting information; experimental part
p. 1858 - 1861
(2012/06/18)
-
- Solvent-free bromination reactions with sodium bromide and oxone promoted by mechanical milling
-
New solvent-free brominations of 1,3-dicarbonyl compounds, phenols, various alkenes including chalcones, azachalcones, 4-phenylbut-3-en-2-one, methyl cinnamate, styrene and 1,3-cyclohexadiene were efficiently achieved by employing sodium bromide and oxone under mechanical milling conditions. The brominated products were obtained in good to excellent yields.
- Wang, Guan-Wu,Gao, Jie
-
experimental part
p. 1125 - 1131
(2012/06/04)
-
- Efficient synthesis and biological evaluation of 4-arylcoumarin derivatives
-
Two bioactive natural 4-arylcoumarins, 5,7,4′-trimethoxy-4- phenylcoumarin (1a), 5,7-dimethoxy-4-phenylcoumarin (1b) and five closely related derivatives 1c-g were synthesized. In vitro evaluation with a catechol subunit for antioxidant and antimicrobial activity, these compounds using standard methods showed that compounds 1d, 1f displayed promise radical scavenging activity and 1f was found to be the most active one against Bacillus dysenteriae.
- Sun, Jie,Ding, Wei Xian,Zhang, Ke Yun,Zou, Yong
-
experimental part
p. 667 - 670
(2012/01/13)
-
- Quantitative structure-activity relationships of pine weevil antifeedants, a multivariate approach
-
Antifeedant activity of mainly phenylpropanoic, cinnamic, and benzoic acids esters was tested on the pine weevil, Hylobius abietis (L.). Of 105 compounds screened for activity, 9 phenylpropanoates, 3 cinnamates, and 4 benzoates were found to be highly active antifeedants. To understand the structure-activity relationships of these compounds, a multivariate analysis study was performed. A number of molecular and substituent descriptors were calculated and correlated to results from two-choice feeding tests with H. abietis. Three local models were developed that had good internal predictive ability. External test sets showed moderate predictivity. In general, low polarity, small size, and high lipophilicity were characteristics for compounds having good antifeedant activity.
- Sunnerheim, Kerstin,Nordqvist, Anneli,Nordlander, Goeran,Borg-Karlson, Anna-Karin,Unelius, C. Rickard,Bohman, Bjoern,Nordenhem, Henrik,Hellqvist, Claes,Karlen, Anders
-
p. 9365 - 9372
(2008/03/17)
-
- A thermal cascade route to pyrroloisoindolone and pyrroloimidazolones
-
(Chemical Equation Presented) Flash vacuum pyrolysis (FVP) of indol-1-ylacrylate derivatives 11 and 15 or the isomeric indol-3-ylacrylates 21, 22, and 24 at 925°C (0.05 Torr) provides pyrrolo[1,2-a]indol-3-ones 2, 18, 28, and 29 in 53-90% yield by a cascade mechanism that involves a sigmatropic migration, elimination, electrocyclization sequence. Pyrrolo[1,2-a]imidazol-5- ones 3 and pyrrolo[1,2-c]imidazol-5-ones 4 were similarly obtained by FVP of corresponding 2,5-unsubstituted imidazol-1-ylacrylates (e.g., 33), with the former isomer predominating in ca. 80:20 ratio. Migration to the 2-position is therefore favored in the initial sigmatropic shift. FVP of 2-substituted imidazol-1-ylacrylates 35, 37, and 51 (825-875°C) instead give pyrrolo[1,2-c]imidazol-5-ones 56-58 only (88-91%), and that of 4,5-disubstituted imidazol-1-ylacrylates 39 and 41 (825-850°C) provide pyrrolo[1,2-a] imidazol-5-ones 59 and 60 exclusively (93-95%), and thus the selectivity of the initial shift can be controlled by the presence of substituents on the imidazole 2- and 5-positions. FVP of the benzimidazole analogues 61 and 62 at 950°C gave the pyrrolo[1,2-a]benzimidazol-1-ones 6 (71%) and 63 (36%), respectively.
- McNab, Hamish,Tyas, Richard G.
-
p. 8760 - 8769
(2008/03/13)
-
- Rapid debromination of vic-dibromoalkanes with zinc powder in acetic acid under microwave irradiation
-
Microwave irradiation of vic-dibromoalkanes in acetic acid containing zinc powder for 1-2 min gave the corresponding alkenes in high yields.
- Kuang, Chunxiang,Yang, Qing,Senboku, Hisanori,Tokuda, Masao
-
p. 282 - 284
(2007/10/03)
-
- Effect of cyclodextrin complexation in bromine addition to unsymmetrical olefins: Evidence for participation of cyclodextrin hydroxyl groups
-
Multiple recognition by cyclodextrin in a bimolecular reaction, namely bromination of styrene, methyl cinnamate, phenylacetylene and allylbenzene, has been studied. Bromohydrin is obtained as a major product along with dibromide in the bromination of styrene and methyl cinnamate. The percentage of bromohydrin decreases as the cavity size increases. With phenylacetylene, bromophenylacetylene and phenacyl bromide are obtained in addition to the dibromides. In the bromination of cyclodextrin complexes of allylbenzene, the product distribution is the same as in solution bromination. The observed results demonstrate the efficiency of cyclodextrin in stabilizing the open carbocationic intermediate and thus provide chemical evidence for the participation of cyclodextrin hydroxyl groups. The Royal Society of Chemistry 2005.
- Manickam, Manickam C. Durai,Annalakshmi, Subramanian,Pitchumani, Kasi,Srinivasan, Chockalingam
-
p. 1008 - 1012
(2007/10/03)
-
- Highly selective reaction of α-halo-αβ-unsaturated esters with ketones or aldehydes promoted by SmI2: An efficient alternative access to Baylis-Hillman adducts
-
A samarium diiodide promoted addition of aromatic or aliphatic β-substituted-α-halo-α,β-unsaturated esters 1 or 3 to both ketones (in THF) and aldehydes (in acetonitrile) led to (Z)-2-(1-hydroxyalkyl)- 2,3-alkenoates 2 and 4 in good yields and very high stereoselectivity. This method constitutes an efficient and valuable alternative to the synthesis of Baylis-Hillman adducts. A mechanism is proposed to explain this transformation.
- Concellon, Jose M.,Huerta, Monica
-
p. 4714 - 4719
(2007/10/03)
-
- An efficient and mild direct oxidative methyl esterification of aromatic aldehydes using NaBr and diacetoxyiodobenzene
-
Diacetoxyiodobenzene combined with NaBr was found to be an efficient, mild and practical reagent for the oxidative methyl esterification of aldehydes.
- Karade,Shirodkar,Dhoot,Waghmare
-
p. 274 - 276
(2007/10/03)
-
- Structure-dependent oxidative bromination of unsaturated C-C bonds mediated by selectfluor
-
A number of olefins were subjected to oxidative bromination using Selectfluor/KBr. For different types of substrates, addition, monobromine-substituted, or Hunsdiecker-Borodin reaction products can be readily afforded.
- Ye, Chengfeng,Shreeve, Jean'Ne M.
-
p. 8561 - 8563
(2007/10/03)
-
- Synthesis of N-bridgehead fused bicyclic β-lactams through organometal-mediated transformations of 1,2-dialkenylaziridines
-
N-Bridgehead fused bicyclic β-lactams have been synthesized through sequential organometal-mediated transformations of 1,2-dialkenylaziridines, namely Co2(CO)8-catalysed carbonylation and ring-closing metathesis (RCM). When firstly subjected to RCM conditions, either with Schrock-Hoveyda or Grubbs' catalyst, 1,2-dialkenylaziridines did not afford the expected bicyclic N-bridgehead products. In contrast, however, cis-1,2-dialkenylaziridines were amenable to carbonylative ring expansion, affording trans-1,4-dialkenyl-β-lactams which could be subsequently metathesized to the corresponding fused bicyclic compounds using Grubbs' catalyst. Unexpectedly, carbonylation of trans-1,2-dialkenylaziridines occurred with the unprecedented rearrangement to the 5,6-dihydro-4H-[1,3]oxazine skeleton.
- Davoli, Paolo,Spaggiari, Alberto,Ciamaroni, Elisa,Forni, Arrigo,Torre, Giovanni,Prati, Fabio
-
p. 2495 - 2514
(2007/10/03)
-
- New palladium(II)-catalyzed asymmetric 1,2-dibromo synthesis
-
(Matrix presented) The oxidation of olefins by chiral monometallic and bimetallic Pd(II)-Cu(II) catalysts in bromide-containing aqueous-THF reaction mixtures produced chiral 1,2-dibromides. With α-olefins, the ee's were about 95% while most of the interna
- El-Qisairi, Arab K.,Qaseer, Hanan A.,Katsigras, George,Lorenzi, Philip,Trivedi, Unnati,Tracz, Sylvia,Hartman, Amy,Miller, Jason A.,Henry, Patrick M.
-
p. 439 - 441
(2007/10/03)
-
- NaIO4-Mediated Selective Oxidative Halogenation of Alkenes and Aromatics Using Alkali Metal Halides
-
(Equation presented) NaIO4 oxidizes alkali metal halides efficiently in aqueous medium to halogenate alkenes and aromatics and produce the corresponding halo derivatives in excellent regio and stereoselectivity. The system also demonstrates the asymmetric version of bromo hydroxylation using β-cyclodextrin complexes, resulting in moderate ee.
- Dewkar, Gajanan K.,Narina, Srinivasarao V.,Sudalai, Arumugam
-
p. 4501 - 4504
(2007/10/03)
-
- An efficient bromination of alkenes using cerium(IV) ammonium nitrate (CAN) and potassium bromide
-
Bromination of alkenes using a combination of potassium bromide and cerium(iv) ammonium nitrate (CAN) in a two phase system consisting of water and dichloromethane affords the corresponding dibromides in excellent yield. The reaction most likely involves the addition of the bromine radical generated from bromide ion by CAN and subsequent formation of the dibromide.
- Nair, Vijay,Panicker, Sreeletha B,Augustine, Anu,George, Tesmol G,Thomas, Siji,Vairamani
-
p. 7417 - 7422
(2007/10/03)
-
- Solvolytic stereoselective debromination of vic-dibromides with HMPA
-
A simple and efficient procedure for the debromination of vic-dibromides has been reported with hexamethylphosphoric triamide at 155-160°C under a nitrogen atmosphere without the aid of any reagent.
- Khurana,Bansal,Chauhan
-
p. 1089 - 1091
(2007/10/03)
-
- Simple and practical halogenation of arenes, alkenes and alkynes with hydrohalic acid/H2O2 or TBHP)
-
A simple protocol for the halogenation of arenes utilizing a combination of aqueous hydrogen peroxide (34 %) or tert-butylhydroperoxide (70 %) and hydrohalic acid is presented. A similar procure of oxyhalogenation involving the in situ generation of positive halogen reagents is applied for the preparation of vicinal trans-dibromoalkanes and dichloroalkanes from alkenes. The reaction of alkenes with a combination of hydrochloric acid and hydrobromic acid with hydrogen peroxide gave a mixture of 1-bromo 2-chloro alkanes and 1,2-dibromoalkanes: Oxidative bromination of alkynes is also reported under similar conditions.
- Barhate, Nivrutti B.,Gajare, Anil S.,Wakharkar, Radhika D.,Bedekar, Ashutosh V.
-
p. 11127 - 11142
(2007/10/03)
-
- Dehalogenation of Vicinal Dibromides by Electrogenerated Polysulfide Ions in Dimethylacetamide
-
Dehalogenation reactions of vic-dibromides by electrogenerated S62- (S3 anion radical), S42- or S32- polysulfide ions have been investigated in dimethylacetamide by use of spectroelectrochemistry on a series of dibromides: methyl erythro-2,3-dibromo-3-phenylpropanoate (1), diethyl meso-2,3-dibromosuccinate (2), meso-1,2-dibromo-1,2-diphenylethane (3), DL-1,2-dibromo-1,2-diphenylethane (4), 1,2-dibromobutane (5), 1,2-dibromophenylethane (6), DL-2,3-dibromobutane (7), erythro-3,4-dibromoheptane (8), threo-3,4-dibromoheptane (9), meso-5,6-dibromodecane (10), trans-1,2-dibromocyclohexane (11).Substitution and elimination are competing mechanism with 5-7 while the quantitative formation of alkenes is observed with the other substituted dibromides.In dilute solutions, indirect electrochemical reductions of vic-dibromides have been performed in the presence of small amounts of sulfur as catalyst at potentials leading to S(-1/3) ions with 1-3, or at more cathodic potentials (formation of S42-/S32- ions) for 8-11.On a preparative scale, stereospecific anti debrominations afford only E alkenes from chemical reaction with 3 or mediated electrolysis of 1,2 or 10.Kinetic studies of the reactions between S(-1/3) ions and compounds 4, 8-10 imply that the dianions S62- are the eliminating agents rather than S3 anion radical ions for the concerted anti dehalogenations.
- Bosser, Gerard,Paris, Jacky
-
p. 2057 - 2063
(2007/10/02)
-
- The effect of polymer-supported reagent structure on bromination of organic molecules
-
Crosslinked poly(styrene-co-4-vinylpyridine) reacted with hydrogen bromide or various alkyl bromides to pyridinium salts, which were further converted with chlorine to polymer supported reagents (1) containing up to 34% of chlorine, while substantial loss
- Zajc, Barbara,Zupan, Marko
-
p. 6161 - 6166
(2007/10/02)
-
- The Compounds Related to 3-(1-Imidazolyl)-2-alken-1-ones. Preparation and Reactions
-
Compounds related to 3-(1-imidazolyl)-2-alken-1-ones, 3-(1-imidazolyl)-2-alkenoic acid derivatives and 2-alken-1-ones having heterocycles on the C-3 carbon were prepared.The reaction of nucleophiles with these compounds was also discussed.
- Kashima, Choji,Tajima, Tadakuni,Omote, Yoshimori
-
p. 171 - 176
(2007/10/02)
-
- A Convenient Synthesis of β-(1-Imidazoyl)enones from α,β-Dibromoketones
-
As the convenient preparative method of β-(substituted)-phenyl-β-(1-imidazolyl)enones, we succeeded in the preparation of β-aryl-β-(1-imidazolyl)enones from α,β-dibromo-β-arylketones with imidazole in the presence of triethylamine.
- Kashima, C.,Shimizu, M.,Tajima, T.
-
p. 961 - 964
(2007/10/02)
-