- Do C-H...O and C-H...π interactions help to stabilize a non-centrosymmetric structure for racemic 2,3-dibromo-1,3-diphenyl-propan-1-one?
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The racemic title compound, C15H12Br2O, crystallizes in a non-centrosymmetric structure and displays a significant non-linear optical response to red light. The crystal packing is influenced by C-H...O and C-H...π interactions. One of the former bonds has a short H...O separation of 2.27 A.
- Harrison, William T. A.,Yathirajan,Sarojini,Narayana,Anilkumar
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Read Online
- Catalyst-Free 1,2-Dibromination of Alkenes Using 1,3-Dibromo-5,5-dimethylhydantoin (DBDMH) as a Bromine Source
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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
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supporting information
p. 3177 - 3183
(2022/02/23)
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- New nicotinic acid-based 3,5-diphenylpyrazoles: design, synthesis and antihyperlipidemic activity with potential NPC1L1 inhibitory activity
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Nicotinic acid hydrazide was incorporated into new 4,5-dihydro-5-hydroxy-3,5-diphenylpyrazol-1-yl derivatives. Compounds 6a–h were synthesized, and their antihyperlipidemic activity was evaluated in high cholesterol diet-fed rat model. Compounds 6e, 6f were found to decrease the levels of serum total cholesterol by 14–19% compared to control group. Total triglycerides were also reduced by 24–28% and LDL cholesterol by 16%. As expected from parent niacin, compounds 6e and 6f caused an elevation of HDL cholesterol by 33–41%. Docking study supported the ability of designed compounds to block NPC1L1 active site in a manner similar to that observed with ezetimibe.
- Shoman, Mai E.,Aboelez, Moustafa O.,Shaykhon, Montaser Sh. A.,Ahmed, Sanaa A.,Abuo-Rahma, Gamal El-Din A.,Elhady, Omar M.
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p. 673 - 686
(2020/02/25)
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- Visible light-mediated metal-free double bond deuteration of substituted phenylalkenes
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Various bromophenylalkenes were reductively photodebrominated by using 1,3-dimethyl-2-phenyl-1H-benzo-[d]imidazoline (DMBI) and 9,10-dicyanoanthracene. With deuterated DMBI analogs (the most effective was DMBI-d11), satisfactory to excellent isotopic yields were obtained. DMBI-d11 could also be regenerated from the reaction mixtures with a recovery rate of up to 50%. The combination of the photodebromination reaction with conventional methods for bromoalkene synthesis enables sequential monodeuteration of a double bond without the necessity of a metal catalyst. This journal is
- Iakovenko, Roman,Hlavá?, Jan
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supporting information
p. 440 - 446
(2021/01/28)
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- Modular access to 1,2-allenyl ketones based on a photoredox-catalysed radical-polar crossover process
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Herein, a new protocol dealing with the preparation of 1,2-allenyl ketones has been successfully developedviathe reactions of enynes with radicals enabled by dual photoredox/copper catalysis. Based on the results of a deuteration experiment and the competition reaction between cyclopropanation and allenation, the mechanism based on a photoredox-neutral-catalysed radical-polar crossover process has been proposed. Synthetic applications of allenes have also been demonstrated.
- Du, Chan,Fang, Jianghua,Fang, Yewen,Lei, Wan,Li, Yan,Liu, Yongjun
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supporting information
p. 8502 - 8506
(2021/10/20)
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- Dibrominated addition and substitution of alkenes catalyzed by Mn2(CO)10
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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
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supporting information
p. 13385 - 13388
(2021/12/17)
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- Synthesis of α,β-dibromo ketones by photolysis of α-bromo ketones with N-bromosuccinimide: Photoinduced β-bromination of α-bromo ketones
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Irradiation of α-bromopropiophenones in the presence of NBS results in the formation of α,β-dibromopropiophenones, which can be viewed as β-bromination of α-bromopropiophenones. The reaction is believed to go through a series of reactions; photoinduced C–Br bond cleavage, elimination of HBr to give α,β-unsaturated ketone intermediates, and addition of Br2, which are formed by the reaction between HBr and NBS. From mechanistic studies of the reaction, we have also found a very convenient method for α-debromination of the α,β-dibromopropiophenones which is by simple irradiation of the dibromo ketones in acetone or 2-propanol without the use of any additives. Our results demonstrate that bromine can be added into or eliminated from the alpha, beta, or both positions to the carbonyl group by photochemical methods, which make synthetic options of bromine containing carbonyl compounds versatile.
- Moon, Da Yoon,An, Sejin,Park, Bong Ser
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- Dibromination of alkenes with LiBr and H2O2 under mild conditions
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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.
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supporting information
p. 161 - 167
(2017/12/28)
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- Solvent free, light induced 1,2-bromine shift reaction of α-bromo ketones
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Photolysis of α-bromopropiophenones in acetonitrile results in formation of β-bromopropiophenones with good product selectivity, which can be coined as 1,2-Br shift reaction. The product selectivity increases when the reaction is done in neat or solid state, where only the 1,2-Br shift product is formed in some cases. The reaction is suggested to proceed by C–Br bond homolysis to give a radical pair, followed by disproportionation and conjugate addition of HBr to the α,β-unsaturated ketone intermediate. When the unsaturated intermediate is stabilized by an extra conjugation, the reaction stops at the stage, in which the unsaturated ketone becomes a major product. The synthetic method described in this research fits in a category of eco-friendly organic synthesis nicely since the reaction does not use volatile organic solvents and any other additives such as acid, base or metal catalysts, etc. Besides, the method fits into perfect atom economy, which does not give any side products. The synthetic method should find much advantage over other alternative methods to obtain β-bromo carbonyl compounds.
- An, Sejin,Moon, Da Yoon,Park, Bong Ser
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p. 6922 - 6928
(2018/10/24)
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- A new synthetic strategy towards 2,4,5-trisubstituted 1H-imidazoles and highly substituted pyrrolo[1,2-c]imidazoles by use of α-azidochalcones via Michael addition-cyclization followed by Wittig reaction
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Efficient and facile protocols for the preparation of highly functionalized 1H-imidazoles and 5H-pyrrolo[1,2-c]imidazoles are described. Heating a mixture of an α-azidochalcones and N,N,N′,N′-tetramethyl guanidine under neat conditions gave the corresponding 2,4,5-trisubstituted 1H-imidazole via Michael addition-cyclization in excellent yields. Subsequently, the prepared 1H-imidazoles undergo addition-Wittig reaction with acetylenic esters in presence of triphenylphosphine in dichloromethane to afford 5H-pyrrolo[1,2-c]imidazoles in high yields.
- Adib, Mehdi,Peytam, Fariba,Rahmanian-Jazi, Mahmoud,Bijanzadeh, Hamid Reza,Amanlou, Massoud
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p. 6696 - 6705
(2017/10/25)
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- Oxygenation of Simple Olefins through Selective Allylic C?C Bond Cleavage: A Direct Approach to Cinnamyl Aldehydes
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A novel metal-free allylic C?C σ-bond cleavage of simple olefins to give valuable cinnamyl aldehydes is reported. 1,2-Aryl or alkyl migration through allylic C?C bond cleavage occurs in this transformation, which is assisted by an alkyl azide reagent. This method enables O-atom incorporation into simple unfunctionalized olefins to construct cinnamyl aldehydes. The reaction features simple hydrocarbon substrates, metal-free conditions, and high regio- and stereoselectivity.
- Liu, Jianzhong,Wen, Xiaojin,Qin, Chong,Li, Xinyao,Luo, Xiao,Sun, Ao,Zhu, Bencong,Song, Song,Jiao, Ning
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supporting information
p. 11940 - 11944
(2017/09/20)
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- Nucleophilic substitution of α-haloenones with phenols
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The α-haloenones undergo cine-substitution upon reaction with phenolic reagents under basic conditions. A convenient method for the synthesis of push-pull aroxyenones was developed based on this reaction.
- Mareev, Alexander V.,Ushakov, Igor A.,Rulev, Alexander Yu.
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p. 1971 - 1974
(2015/03/30)
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- Experimental and Theoretical Study of an Intramolecular CF3-Group Shift in the Reactions of α-Bromoenones with 1,2-Diamines
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The reactions of trifluoromethylated 2-bromoenones and N,N′-dialkyl-1,2-diamines have been studied. Depending on the structures of the starting compounds, the formation of 2-trifluoroacetylpiperazine or 3-trifluoromethylpiperazine-2-ones was observed. The mechanism of the reaction is discussed in terms of multistep processes involving sequential substitution of bromine in the starting α-bromoenones and intramolecular cyclization of the captodative aminoenones as key intermediates to form the target heterocycles. The results of theoretical calculations are in perfect agreement with the experimental data. The unique role of the trifluoromethyl group in this reaction is demonstrated.
- Muzalevskiy, Vasily M.,Ustynyuk, Yury A.,Gloriozov, Igor P.,Chertkov, Vyacheslav A.,Rulev, Alexander Yu.,Kondrashov, Evgeniy V.,Ushakov, Igor A.,Romanov, Alexey R.,Nenajdenko, Valentine G.
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p. 16982 - 16989
(2015/11/16)
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- Four-component reaction leading to highly functionalized sulfoalkoxy carbonyl compounds
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A facile regio- and diastereoselective four-component protocol has been developed involving an α,β-unsaturated carbonyl compound, a cyclic ether, a sulfonic acid and a halogen reagent to access highly anti-α-bromo-β-sulfoalkoxyl carbonyl derivatives. Some of these products have high toxicity against human chronic myeloid leukemia cells.
- Sohail, Muhammad,Zhang, Yixin,Sun, Guangwei,Guo, Xin,Liu, Wujun,Liu, Chang,Zhao, Zongbao K.
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supporting information
p. 4774 - 4777
(2015/03/18)
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- I2O5-mediated bromohydroxylation and dibromination of olefins using KBr in water
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An efficient and green bromohydroxylation and dibromination of various olefins mediated by I2O5 has been developed in this work. A series of olefins gave the corresponding α-bromo-alcohols and dibromides as the major products using KBr as the brominating reagent in aqueous medium at room temperature. The diastereo- and regio-selectivities are extremely high.
- Wang, Yajun,Wang, Jinxi,Xiong, Yun,Liu, Zhong-Quan
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supporting information
p. 2734 - 2737
(2014/05/06)
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- Brominations with Pr4NBr9 as a solid reagent with high reactivity and selectivity
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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
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p. 740 - 747
(2014/04/03)
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- Halocarbocyclization versus dihalogenation: Substituent directed iodine(iii) catalyzed halogenations
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The nucleophilicity of the substituents in iodobenzene pre-catalysts have a huge impact on product selectivity in iodine(iii) triggered halogenations, steering the reactivity from solely carbocyclizations towards dihalogenations. Utilizing this catalyst-dependent reactivity a diastereo- and chemoselective dihalogenation method was established allowing the conversion of structurally and electronically diverse unsaturated compounds in excellent yields.
- Stodulski, Maciej,Goetzinger, Alissa,Kohlhepp, Stefanie V.,Gulder, Tanja
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supporting information
p. 3435 - 3438
(2014/03/21)
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- One-pot three-component approach to the synthesis of polyfunctional pyrazoles
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A simple, multicomponent, and straightforward reaction of vinyl azide, aldehyde, and tosylhydrazine affords the construction of 3,4,5-trisubstituted 1H-pyrazoles regioselectively in the presence of base with moderate to excellent yields. A range of functionality could be tolerated in this methodology, and a possible mechanism is proposed.
- Zhang, Guolin,Ni, Hangcheng,Chen, Wenteng,Shao, Jiaan,Liu, Huan,Chen, Binhui,Yu, Yongping
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supporting information
p. 5967 - 5969
(2014/01/06)
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- An old story in new light: X-ray powder diffraction provides novel insights into a long-known organic solid-state rearrangement reaction
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The first in situ diffraction study of the long-known solid-state rearrangement of p-bromobenzeneazotribenzoylmethane is reported. This proof-of-principle study demonstrates how modern laboratory X-ray powder diffraction, accompanied by up-to-date processing tools, can be used to monitor and describe mechanisms of organic solid-state reactions while it also underpins its necessity for structural characterisation of in situ formed crystalline phases.
- Halasz, Ivan,Cindro, Nikola,Dinnebier, Robert E.,Vancik, Hrvoj
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p. 187 - 192
(2013/11/06)
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- Ecofriendly bromination of chalcones and synthesis of flavones using grinding technique
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Selective bromination of chalcones and 2'-hydroxychalcones has been carried out with ammonium bromide and ammonium persulphate using grinding technique at RT under aqueous moist condition to give α,β-dibromochalcones and α,β-dibromo-2'- hydroxychalcones respectively. α,β- Dibromo-2'-hydroxychalcones have been cyclodehydrobrominated with barium hydroxide moist and ethanol at RT to give flavones using grinding technique.
- Jakhar, Komal,Makrandi
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p. 141 - 145
(2013/02/23)
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- Alkoxybromination of olefins using ammonium bromide and oxone
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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
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supporting information
p. 3121 - 3129
(2014/01/06)
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- Direct sustainable bromination of alkenes in aqueous media and basic ionic liquids
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Electron-rich and electron-poor alkenes have been dibrominated using a rapid and sustainable procedure. The reactions were conducted in aqueous medium and basic ionic liquids which catalyzed the direct addition of bromine. The protocol leads to remarkable results, high yields under mild conditions, complete chemo- and stereo-selectivity and allows the recycling of ionic liquids, reducing costs, and environmental impact.
- Primerano, Patrizia,Cordaro, Massimiliano,Scala, Angela
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p. 4061 - 4063
(2013/07/25)
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- Aqueous Et4NBrO3/KBr as a versatile and environmentally benign source of bromine for the selective trans-bromination of alkenes
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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
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p. 802 - 806
(2013/07/26)
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- Organocatalysis as a safe practical method for the stereospecific dibromination of unsaturated compounds
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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.
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supporting information; experimental part
p. 1858 - 1861
(2012/06/18)
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- Regio-and stereoselective hydroxybromination and dibromination of olefins using ammonium bromide and oxone
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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
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supporting information; experimental part
p. 1401 - 1405
(2012/04/04)
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- Solvent-free bromination reactions with sodium bromide and oxone promoted by mechanical milling
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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
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experimental part
p. 1125 - 1131
(2012/06/04)
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- Chemoselective C-C bond cleavage of epoxide motifs: Gold(I)-catalyzed diastereoselective [4+3] cycloadditions of 1-(1-Alkynyl)oxiranyl ketones and nitrones
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Cutting carbon! A novel facile strategy for the C-C bond cleavage of oxiranyl ketones has been developed. Carbophilic gold(I) activation of the alkyne side chain mediates a heterocyclization and subsequent C-C bond cleavage (see scheme).
- Wang, Tao,Zhang, Junliang
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scheme or table
p. 86 - 90
(2011/03/20)
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- Visible-light photoredox catalysis: Dehalogenation of vicinal dibromo-, α-halo-, and α,α-dibromocarbonyl compounds
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vic-Dibromo-, α-halo-, or α,α-dibromocarbonyl compounds can be efficiently dehalogenated using catalytic tris(2,2′-bipyridyl) ruthenium dichloride (Ru(bpy)3Cl2) in combination with 1,5-dimethoxynaphthalene (DMN) and ascorbate as sacrificial electron donor. For this process, a visible light promoted photocatalytic cycle is proposed that involves the reduction of carbon halogen bonds via free radical intermediates.
- Maji, Tapan,Karmakar, Ananta,Reiser, Oliver
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supporting information; experimental part
p. 736 - 739
(2011/03/20)
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- Electrophilic bromination of alkenes, alkynes, and aromatic amines with iodic acid/potassium bromide under mild conditions
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Bromination of alkenes, alkynes, and aromatic amines has efficiently been carried out at room temperature in short reaction times using HIO 3/KBr in CH2Cl2/H2O (1:1) to prepare corresponding brominated compounds in excellent yields.
- Khazaei, Ardeshir,Zolfigol, Mohammad Ali,Kolvari, Eskandar,Koukabi, Nadiya,Soltani, Hamid,Bayani, Leyla Sharaf
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experimental part
p. 2954 - 2962
(2010/10/20)
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- Facile one-pot synthesis of α-bromoketones from olefins using bromide/bromate couple as a nonhazardous brominating agent
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A new method for the preparation of α-bromoketones from olefins using bromide/bromate couple as a nonhazardous brominating agent has been developed. Several α-bromoketones were successfully prepared from a variety of olefins by this method. This procedure is an alternative to conventional molecular bromine.
- Patil, Rajendra D.,Joshi, Girdhar,Adimurthy, Subbarayappa,Ranu, Brindaban C.
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experimental part
p. 2529 - 2532
(2009/09/06)
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- Efficient bromination of alkenes and alkynes using potassium bromide and diacetoxy iodobenzene
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Bromination of alkenes and alkynes has efficiently been carried out at room temperature in short reaction times using KBr and diacetoxy iodobenzene in CH2Cl2-H2O (1:1) to prepare the corresponding trans-dibromo compounds in excellent yields. Copyright Taylor & Francis Group, LLC.
- Das, Biswanath,Srinivas, Yallamalla,Sudhakar, Chittaluri,Damodar, Kongara,Narender, Ravirala
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experimental part
p. 220 - 227
(2009/04/07)
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- Elctrophilic bromination of alkenes, alkynes, and aromatic amines with potassium bromide/orthoperiodic acid under mild conditions
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Bromination of alkenes, alkynes, and aromatic amines has efficiently been carried out at room temperature in short reaction times using potassium bromide/orthoperiodic acid in dichloromethane-water (1:1) to prepare the corresponding bromo compounds with excellent yields.
- Khazaei, Ardeshir,Zolfigol, Mohammad Ali,Kolvari, Eskandar,Koukabi, Nadiya,Soltani, Hamid,Komaki, Fatemeh
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experimental part
p. 3672 - 3676
(2010/04/05)
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- 79Br NMR spectroscopy as a practical tool for kinetic analysis
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79Br NMR spectroscopy has been used to monitor a series of reactions in which the bromide ion is produced, including the Menschutkin reaction of pyridine with a range of substituted benzyl bromides and a Heck coupling process. In cases where the process could also be monitored using 1H NMR spectroscopy, the kinetic analyses using heteronuclear magnetic resonance spectroscopy were shown to be completely consistent. Both the utility of the process in following reactions which may be difficult to analyse using other techniques and the practical limitations associated with solvent choice are discussed. Copyright
- Chan, Si Jia,Howe, Andrew G.,Hook, James M.,Harper, Jason B.
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experimental part
p. 342 - 347
(2010/02/27)
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- Bromination of alkenes and alkynes with (bromodimethyl)sulfonium bromide
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Alkenes and alkynes were brominated efficiently in high yields with (bromodimethyl)sulfonium bromide in acetonitrile at room temperature. Alkenes produced the corresponding trans-dibromo compounds while alkynes (except phenylacetylene) afforded both the trans-dibromo products (major) and the tetrabromo derivatives (minor). However, phenylacetylene furnished solely the tetrabromo compound.
- Das, Biswanath,Srinivas, Yallamalla,Sudhakar, Chittaluri,Ravikanth, Bommena
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experimental part
p. 188 - 190
(2009/07/18)
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- Aminobromination of olefins with TsNH2 and NBS as the nitrogen and bromine sources mediated by hypervalent iodine in a ball mill
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A series of olefins including α,β-unsaturated ketones, cinnamates, cinnamides and styrenes have been aminobrominated with good yields and excellent diastereoselectivities under mechanical milling conditions, using TsNH2 and NBS as the nitrogen and bromine sources, promoted by (diacetoxyiodo)benzene. The Royal Society of Chemistry 2008.
- Wu, Xue-Liang,Xia, Jing-Jing,Wang, Guan-Wu
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scheme or table
p. 548 - 553
(2008/10/09)
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- Aminohalogenation of electron-deficient olefins promoted by hypervalent iodine compounds
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An efficient and practical procedure for the aminohalogenation of electron-deficient olefins promoted by hypervalent iodine compounds has been demonstrated. The catalytic efficiency of various hypervalent iodine compounds with different carboxylic and sulfonic ligands has also been investigated and of these (diacetoxyiodo)benzene exhibited the highest activity. A series of substrates, including α,β-unsaturated ketones, cinnamates, and cinnamides, were tolerable under the conditions employed and were aminochlorinated/-brominated in good yields and with excellent diastereo-selectivities. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Wu, Xue-Liang,Wang, Guan-Wu
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body text
p. 6239 - 6246
(2009/06/18)
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- Microwave-assisted dehalogenation of α-haloketones by zinc and ammonium chloride in alcohol
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The treatment of α-haloketones with 1.5 equiv. of Zn and 1 equiv. of NH4Cl in ethanol for 0.5αmin gave the corresponding ketones with excellent yields under microwave irradiation. Vic-dibromides and 2,2-dibromoacetophenone can be efficiently debrominated to alkenes and acetophenones, respectively. Copyright Taylor & Francis Group, LLC.
- Li, Jian,Ye, Deju,Liu, Hong,Luo, Xiaoming,Jiang, Hualiang
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p. 567 - 575
(2008/04/12)
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- Poly(vinylpyrrolidone)-bromine complex; a mild and efficient reagent for selective bromination of alkenes and oxidation of alcohols
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Poly(vinylpyrrolidone)-bromine complex (PVP-Br2) is easily prepared and used as a mild and convenient reagent for selective bromination of alkenes and at the position α-hydrogen of active carbonyl compounds. Selective oxidation of benzylic alcohols in the presence of aliphatic alcohols were also achieved at room temperature.
- Lakouraj, Moslem Mansour,Tajbakhsh, Mahmood,Mokhtary, Masoud
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p. 481 - 483
(2007/10/03)
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- The important role of solvent vapor in an organic solid state reaction
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Some organic reactions in the solid state proceeded very efficiently and selectively in the presence of a small amount of solvent vapor. The Royal Society of Chemistry 2005.
- Nakamatsu, Seiken,Toyota, Shinji,Jones, William,Toda, Fumio
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p. 3808 - 3810
(2007/10/03)
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- A new recyclable ditribromide reagent for efficient bromination under solvent free condition
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1,2-Dipyridiniumditribromide-ethane (DPTBE) has been synthesized and explored as a new efficient brominating agent. The crystalline ditribromide reagent is stable for months and acts as a safe source of bromine requiring just 0.5 equiv for complete bromination. It has high active bromine content per molecule and shows a remarkable reactivity compared to other tribromide reagents toward various substrates by just grinding the reagent and substrates in a porcelain mortar at room temperature. No organic solvent has been used during any stage of the reaction for substrates giving product as solid. Product can easily be isolated by just washing the highly water soluble 1,2- dipyridiniumdibromide-ethane (DPDBE) from the brominated product. The spent reagent can be recovered, regenerated, and reused without any significant loss.
- Kavala, Veerababurao,Naik, Sarala,Patel, Bhisma K.
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p. 4267 - 4271
(2007/10/03)
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- Pentylpyridinium tribromide: A vapor pressure free room temperature ionic liquid analogue of bromine
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The synthesis and characterization of the room temperature ionic liquid pentylpyridinium tribromide (2) is described. Tribromide 2 was used as a vapor pressure free bromine analogue for the bromination of ketones, aromatics, alkenes, and alkynes. The brominations were carried out in the absence of organic solvents and in most cases the only extraction solvent needed was water. Selectivities and reactivities were shown to be superior to current protocols. The spent reagent pentylpyridinium bromide (1) was easily recycled.
- Salazar, José,Dorta, Romano
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p. 1318 - 1320
(2007/10/03)
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- Structure-dependent oxidative bromination of unsaturated C-C bonds mediated by selectfluor
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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.
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p. 8561 - 8563
(2007/10/03)
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- Synthesis of allenes from allylic alcohol derivatives bearing a bromine atom using a palladium(0)/diethylzinc system
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A general and efficient synthesis of allenes using a palladium(0)/diethylzinc system is described. Treatment of mesylates or trichloroacetates of (E)- or (Z)-2-bromoalk-2-en-1-ols with diethylzinc in the presence of a catalytic amount of palladium(0) affords allenes bearing an aminoalkyl, alkyl, or aryl substituent(s) in good to high yields. No transfer of chirality from the stereogenic center carrying the mesyloxy group to the allene was observed.
- Ohno, Hiroaki,Miyamura, Kumiko,Tanaka, Tetsuaki,Oishi, Shinya,Toda, Ayako,Takemoto, Yoshiji,Fujii, Nobutaka,Ibuka, Toshiro
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p. 1359 - 1367
(2007/10/03)
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- An efficient bromination of alkenes using cerium(IV) ammonium nitrate (CAN) and potassium bromide
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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
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p. 7417 - 7422
(2007/10/03)
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- Solvolytic stereoselective debromination of vic-dibromides with HMPA
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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
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p. 1089 - 1091
(2007/10/03)
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- A new method for stereoselective bromination of stilbene and chalcone in a water suspension medium
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Bromination reactions of (E)-stilbene and (E)-chalcone in a water suspension medium proceeded efficiently and stereoselectively, and the reaction products were collected easily by filtration. The Royal Society of Chemistry 1999.
- Tanaka, Koichi,Shiraishi, Ryusukc,Toda, Fumio
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p. 3069 - 3070
(2007/10/03)
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- Simple and practical halogenation of arenes, alkenes and alkynes with hydrohalic acid/H2O2 or TBHP)
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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.
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p. 11127 - 11142
(2007/10/03)
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- Bromination of alkenes using a mixture of sodium bromide and sodium perborate
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Bromination of alkenes with sodium bromide in the presence sodium perborate provides a simple, high yield route to dibromoalkanes.
- Kabalka,Yang,Reddy,Narayana
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p. 925 - 929
(2007/10/03)
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- An environmentally benign synthesis of organic ammonium tribromides (OATB) and bromination of selected organic substrates by tetrabutylammonium tribromide (TBATB)
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Stable crystalline organic ammonium tribromides (OATB), like Me4NBr3, Et4NBr3, Bu4NBr3, cetyltrimethylammonium tribromide, PyHBr3, can be readily synthesised from the reaction of the corresponding bromides with V2O5 and aqueous H2O2. Typically, TBATB, Bu4NBr3, brominates a variety of organic substrates rather easily under mild conditions. An activated aromatic ring is selectively brominated in the presence of an olefinic double bond.
- Chaudhuri, Mihir K.,Khan, Abu T.,Patel, Bhisma K.,Dey, Deepa,Kharmawophlang, Wancydora,Lakshmiprabha,Mandal, Gagan C.
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p. 8163 - 8166
(2007/10/03)
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- New Derivatives of N-Vinyltriazoles: 1,3-Diaryl-3-(1H-1,2,4-triazol-1-yl)-2-propen-1-ones
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We have synthesized previously unknown N-vinyltriazoles: 1,3-diaryl-3-(1H-1,2,4-triazol-1-yl)-2-propen-1-ones.We discusss a hypothesis for a probable reaction mechanism.
- Rekhter, M. A.,Grushetskaya, G. N.,Panasenko, A. A.,Krimer, M. Z.
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p. 792 - 796
(2007/10/03)
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