- 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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- Chemical validation of a druggable site on Hsp27/HSPB1 using in silico solvent mapping and biophysical methods
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Destabilizing mutations in small heat shock proteins (sHsps) are linked to multiple diseases; however, sHsps are conformationally dynamic, lack enzymatic function and have no endogenous chemical ligands. These factors render sHsps as classically “undruggable” targets and make it particularly challenging to identify molecules that might bind and stabilize them. To explore potential solutions, we designed a multi-pronged screening workflow involving a combination of computational and biophysical ligand-discovery platforms. Using the core domain of the sHsp family member Hsp27/HSPB1 (Hsp27c) as a target, we applied mixed solvent molecular dynamics (MixMD) to predict three possible binding sites, which we confirmed using NMR-based solvent mapping. Using this knowledge, we then used NMR spectroscopy to carry out a fragment-based drug discovery (FBDD) screen, ultimately identifying two fragments that bind to one of these sites. A medicinal chemistry effort improved the affinity of one fragment by ~50-fold (16 μM), while maintaining good ligand efficiency (~0.32 kcal/mol/non-hydrogen atom). Finally, we found that binding to this site partially restored the stability of disease-associated Hsp27 variants, in a redox-dependent manner. Together, these experiments suggest a new and unexpected binding site on Hsp27, which might be exploited to build chemical probes.
- Makley, Leah N.,Johnson, Oleta T.,Ghanakota, Phani,Rauch, Jennifer N.,Osborn, Delaney,Wu, Taia S.,Cierpicki, Tomasz,Carlson, Heather A.,Gestwicki, Jason E.
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- Stable and Highly Regioselective Anionic Polymerization of (Z)-1-Phenyl[3]dendralene
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The anionic polymerization of (Z)-1-phenyl[3]dendralene (1Z-P3D) in THF with potassium naphthalenide (K-Naph) as an initiator was investigated. At -78 °C, a polymer of predictable molecular weight and narrow molecular-weight distribution (Mw/Mn = 1.26) was obtained quantitively in 24 h. The active chain-end carbanion derived from 1Z-P3D was significantly stabilized by conjugation with a phenyl substituent at the C1 position of the monomer; side reactions such as nucleophilic addition to the double bond in other polymer main chains were not observed over a wide temperature range (-78-0 °C). The microstructure of the obtained poly(1Z-P3D) contained a predominant amount of the 1,4 structure (>90%). Thus, the polymerizability of 1Z-P3D was different from that of previously reported 2-phenyl[3]dendralene (P3D), in terms of the nucleophilicity of the active chain end and regioselectivity in the propagation reaction.
- Miya, Masamitsu,Takagi, Tsukasa,Takenaka, Katsuhiko,Toda, Tomoyuki
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p. 4326 - 4332
(2021/05/29)
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- Synthesis method of o-Dibromo compound
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The present invention discloses a synthesis method of o-dibromo compounds, said synthesis method comprising the following steps: preparation of olefins, brominated salts and a mixed solution of bromate; to the mixed solution of dropwise addition of hydrochloric acid solution for reaction; to the end of the reaction, the extraction of o-dibromo compounds in the reaction product; the synthesis method to inexpensive brominated salts (industrial or recycled brominated salts) and bromate as a bromine source, enhance the full use of applicable resources; after the end of the reaction after a simple filtration treatment to obtain a sufficient purity of the product, It can reduce production costs; at the same time, facilitate the transportation and storage of raw materials, and improve the working environment. The synthesis method of the present invention is simple and easy to operate, high safety, small pollution, simple post-treatment, low production cost, product yield and purity can meet the production needs, is both cost advantages and safety and environmental advantages of the industrializable process.
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-
Paragraph 0042-0051
(2022/01/04)
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- Crystal structure, characterization, Hirshfeld surface analysis and DFT studies of two [propane 3-bromo-1-(triphenyl phosphonium)] cations containing bromide (I) and tribromide (II) anions: The anion (II) as a new brominating agent for unsaturated compounds
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In this study, propane 3-bromo-1- (triphenyl phosphonium) bromide, I, and propane 3-bromo-1- (triphenyl phosphonium) tribromide, II, (II as a new brominating agent) were synthesized and characterized by 1H NMR, 13C NMR, 31P NMR, FT-IR, spectroscopy, Thermogravimetric Analysis, Differential thermal analysis, Differential scanning calorimetry and single crystal X-ray analysis. Density functional theory calculations (energy, structural optimization and frequencies, Natural Bond Orbital, absorption energy and binding energy) were performed by using B3LYP/6-311 G++ (d, p) level of theory. Hirshfeld surface analysis and fingerprint plots were utilized to investigate the role of bromide and tribromide anions on the crystal packing structures of title compounds. The results revealed that the change of accompanying anionic moiety can affect the directional interactions of C-H?Br hydrogen bonds between anionic and cationic units in which the H?Br with a proportion of 53.8% and 40.9% have the major contribution in the stabilization of crystal structures of I and II, respectively. Furthermore, the thermal stability of new brominating agent II with tribromide anion was compared with compound I with bromide anion. Nontoxicity, short reaction time, thermal stability, simple working up and high yield are some of the advantages of these salts.
- Nokhbeh, Seyed Reza,Gholizadeh, Mostafa,Salimi, Alireza,Sparkes, Hazel A.
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p. 542 - 554
(2019/06/18)
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- A Facile Access to trans -3-Styryl-4-hydrazinocyclopentenes via Palladium-Catalyzed Ring Opening of Diazanorbornenes with (Z)-β-Bromostyrenes/2,3-Dibromohydrocinnamic Acids
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trans -3-Styryl-4-hydrazinocyclopentenes have been synthesized via palladium-catalyzed desymmetrization of diazanorbornenes with (Z)-β-bromostyrenes. The reaction also works well with (Z)-β-bromostyrenes generated in situ from 2,3-dibromohydrocinnamic acids. The synthesized hydrazinocyclopentenes provide an easy route towards synthetic intermediates of many scaffolds of biological potential.
- Saranya,Chand, S. Sarath,Gopalan, Greeshma,Jijitha,Radhakrishnan
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p. 184 - 192
(2017/10/13)
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- Ir-Catalyzed Intramolecular Transannulation/C(sp2)-H Amination of 1,2,3,4-Tetrazoles by Electrocyclization
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An efficient strategy for the intramolecular denitrogenative transannulation/C(sp2)-H amination of 1,2,3,4-tetrazoles bearing C8-substituted arenes, heteroarenes, and alkenes is described. The process involves the generation of the metal-nitrene intermediate from tetrazole by the combination of [CpIrCl2]2 and AgSbF6. It has been shown that the reaction proceeds via an unprecedented electrocyclization process. The method has been successfully applied for the synthesis of a diverse array of α-carbolines and 7-azaindoles.
- Das, Sandip Kumar,Roy, Satyajit,Khatua, Hillol,Chattopadhyay, Buddhadeb
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supporting information
p. 8429 - 8433
(2018/07/09)
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- Chloro/bromotrimethylsilane-Cu(NO3)2·3H2O: Safe and efficient reagent system for the decarboxylative ipso-nitration and dibromination of cinnamic acids
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Further synthetic potential of halotrimethylsilane-nitrate salt mixture is revealed. A mixture of TMSX-Cu(NO3)2·3H2O system is found to be an efficient reagent system for both the decarboxylative nitration (ipso-nitration) when X?=?Cl, and dibromination of cinnamic acids, with X?=?Br, under mild conditions. The reactions are safe and simple, affording the corresponding products (E)-β-nitrostyrenes, and anti-2,3-dibromo-3-phenylpropanoic acids in high yields with high selectivity in a relatively short time. Use of hazardous and toxic nitrating systems such as acetyl nitrate and brominating agents such as molecular bromine can be avoided.
- Roshandel, Sahar,Gurung, Laxman,Mathew, Thomas,Prakash, G.K. Surya
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supporting information
p. 2842 - 2845
(2017/06/27)
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- Carbene-catalyzed LUMO activation of alkyne esters for access to functional pyridines
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A carbene-catalyzed LUMO activation of α,β-unsaturated alkyne esters is reported. This catalytic process allows for effective reactions of alkyne esters with enamides to synthesize functional pyridines via simple protocols. A previously unexplored unsaturated alkyne acyl azolium intermediate is involved in the key step of the reaction.
- Mou, Chengli,Wu, Jichang,Huang, Zhijian,Sun, Jun,Jin, Zhichao,Chi, Yonggui Robin
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p. 13359 - 13362
(2017/12/26)
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- Electrochemical bromination of cyclic and acyclic enes using biphasic electrolysis
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A simple method of electrochemical bromination of a series of cyclic and acyclic enes (styrene and substituted styrenes, stilbene, indene, and cyclooctene) in a biphasic water-chloroform mixture mediated by bromide/bromine redox system is reported. Aqueous 25% NaBr/H2SO4 is used as the electrolyte. Regio- and stereoselective dibromination of enes is achieved. Moderate to excellent yields of the product (83-98%) is obtained depending on the substrate. Electrolyte reuse has also been demonstrated successfully using HBr in the dibromination of styrene.
- Kulangiappar,Ramaprakash,Vasudevan,Raju
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supporting information
p. 145 - 153
(2016/02/23)
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- Preparation of Vinyl Arenes by Nickel-Catalyzed Reductive Coupling of Aryl Halides with Vinyl Bromides
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This work emphasizes the synthesis of substituted vinyl arenes by reductive coupling of aryl halides with vinyl bromides under mild and easy-to-operate nickel-catalyzed reaction conditions. A broad range of aryl halides, including heteroaromatics, and vinyl bromides were employed to yielding products in moderate to excellent yields with high functional-group tolerance. The nickel-catalytic system displays good chemoselectivity between the two C(sp2)-halide coupling partners, thus demonstrating a mechanistic pathway distinct from other stepwise protocols.
- Liu, Jiandong,Ren, Qinghua,Zhang, Xinghua,Gong, Hegui
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supporting information
p. 15544 - 15548
(2016/12/09)
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- Pd-Catalyzed C(sp3)-C(sp2) cross-coupling of Y(CH2SiMe3)3(THF)2 with vinyl bromides and triflates
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Pd-Catalyzed C(sp3)-C(sp2) cross-coupling of Y(CH2SiMe3)3(THF)2 with vinyl bromides and triflates has been developed for efficient synthesis of various allyltrimethylsilanes. The cross-coupling reaction was conducted at room temperature with low catalyst loading of either Pd(PPh3)4 or Pd(PPh3)2Cl2, and exhibited high efficiency and a broad substrate scope. In combination with the cross-coupling by the Lewis-acid catalyzed Hosomi-Sakurai reaction, a novel three-component one-pot cascade reaction was then accomplished to deliver homoallylic alcohols and ethers with high regioselectivity and diastereoselectivity. The three-component reaction defined the yttrium complex as a novel one-carbon synthon, which could either trigger bifunctionalization of alkenes or link two electrophiles and would find applications in organic synthesis.
- Cai, Guilong,Zhou, Zhibing,Wu, Wenchao,Yao, Bo,Zhang, Shaowen,Li, Xiaofang
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supporting information
p. 8702 - 8706
(2016/10/03)
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- Palladium-Catalyzed Two-Component Domino Coupling Reaction of (Z)-β-Bromostyrenes with Norbornenes: Synthesis of 1,5-Enynes
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Polyfunctional molecules, 1,5-enynes, have been achieved via a palladium(0)-catalyzed domino coupling reaction of (Z)-β-bromostyrenes with norbornenes in the presence of cesium carbonate and N,N-dimethylformamide. The process involves a double Heck-type procedure, two-fold C(sp2) H activation and formation of two carbon-carbon bonds. There are possibilities of diversified transformation for the domino coupling of (Z)-β-bromostyrenes with norbornenes, the procedure is successfully driven to 1,5-enynes via accurate adjustment of the reaction conditions. (Figure presented.) .
- Mao, Jiangang,Li, Huifang,Wen, Herui,Li, Min,Fan, Xiaolin,Bao, Weiliang
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p. 1873 - 1879
(2016/07/06)
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- LSD1 INHIBITORS AND USES THEREOF
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Provided are novel compounds of Formula (I) and pharmaceutically acceptable salts thereof, which are useful for treating a variety of diseases, disorders or conditions, associated with LSDl. Also provided are pharmaceutical compositions comprising the novel compounds of Formula (I), pharmaceutically acceptable salts thereof, and methods for their use in treating one or more diseases, disorders or conditions, associated with LSDl.
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- Palladium(0)-Catalyzed Methylcyclopropanation of Norbornenes with Vinyl Bromides and Mechanism Study
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An unusual methylcyclopropanation from [2 + 1] cycloadditions of vinyl bromides to norbornenes catalyzed by Pd(OAc)2/PPh3 in the presence of CH3ONa and CH3OH has been established. A methylcyclopropane subunit was installed by a 3-fold domino procedure involving a key protonation course. Preliminary deuterium-labeling studies revealed that the proton came from methyl of CH3OH and also exposed an additional hydrogen/deuterium exchange process. These two proton-concerned reactions were fully chemoselective.
- Mao, Jiangang,Xie, Hujun,Bao, Weiliang
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p. 3678 - 3681
(2015/08/18)
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- Palladium(0)-catalyzed methylenecyclopropanation of norbornenes with vinyl bromides
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Highly strained methylenecyclopropane derivatives have been achieved via a novel and efficient Pd(0)-catalyzed domino reaction. The formal [2 + 1] cycloaddition reaction of vinyl bromides to norbornenes involves a Heck-type coupling and a C(sp2)-H bond activation.
- Mao, Jiangang,Bao, Weiliang
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p. 2646 - 2649
(2014/06/09)
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- Palladium-catalyzed [2+1+1] annulation of norbornenes with (z)-bromostyrenes: Synthesis of bismethylenecyclobutanes via twofold C(sp2)-H bond activation
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The first Pd-catalyzed intermolecular [2+1+1] annulation reaction of (Z)-bromostyrene derivatives and norbornenes has been realized. Bismethylenecyclobutane derivatives were obtained with high yields. The domino coupling reaction involves a double Heck-type coupling process, twofold C(sp2)-H bond activation and formation of three carbon-carbon bonds.
- Mao, Jiangang,Bao, Weiliang
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p. 15726 - 15729
(2015/01/08)
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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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- Formation of quaternary stereogenic centers by copper-catalyzed asymmetric conjugate addition reactions of alkenylaluminums to trisubstituted enones
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Alkenylaluminums undergo asymmetric copper-catalyzed conjugate addition (ACA) to β-substituted enones allowing the formation of stereogenic all-carbon quaternary centers. Phosphinamine-copper complexes proved to be particularly active and selective compared with phosphoramidite ligands. After extensive optimization, high enantioselectivities (up to 96 % ee) were obtained for the addition of alkenylalanes to β-substituted enones. Two strategies for the generation of the requisite alkenylaluminums were explored allowing for the introduction of aryl- and alkyl-substituted alkenyl nucleophiles. Moreover, alkyl-substituted phosphinamine (SimplePhos) ligands were identified for the first time as highly efficient ligands for the Cu-catalyzed ACA. Chiral synthesis made easy: The copper-catalyzed conjugate addition of alkenylaluminum reagents to 3-substituted cyclic enones allows for the formation of all-carbon chiral quaternary centers (see scheme; CuTC=copper(I) thiophene-2-carboxylate). Chiral phosphinamine (SimplePhos) ligands were found to be highly efficient for this transformation.
- Mueller, Daniel,Alexakis, Alexandre
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supporting information
p. 15226 - 15239
(2013/11/06)
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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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- Palladium-catalyzed oxidative intramolecular C-C bond formation via double sp2 C-H activation between the 2-position of imidazoles and a benzene ring
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Oxidative intramolecular C-C bond formation via double sp2 C-H activation between the 2-position of imidazoles and a benzene ring catalyzed by palladium(II) has been developed, which provides an atom-economical, concise and efficient methodology to synthesize imidazole- or benzimidazole-fused isoquinoline polyheteroaromatic compounds. Copyright
- Sun, Manman,Wu, Huandong,Zheng, Junnan,Bao, Weiliang
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p. 835 - 838
(2012/05/20)
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- Convenient synthesis of terminal alkynes from anti-3-aryl-2,3- dibromopropanoic acids using a K2CO3/DMSO system
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A convenient, efficient, and generally applicable method was developed for the synthesis of terminal alkynes from anti-3-aryl-2,3-dibromopropanoic acids in the presence of DMSO and K2CO3.
- Cheng, Xuezhi,Jia, Jun,Kuang, Chunxiang
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experimental part
p. 2350 - 2354
(2012/02/03)
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- Dioxane dibromide-mediated solvent-free synthesis of vicinal dibromides
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Structurally varied vicinal dibromides have been synthesized in high yield and good purity through highly stereoselective anti-addition of bromine across the olefinic linkages using dioxane dibromide (DD) under solvent-free conditions. Copyright Taylor & Francis Group, LLC.
- Chaudhuri, Subrata Kumar,Roy, Sanchita,Saha, Manabendra,Bhar, Sanjay
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p. 271 - 274
(2007/10/03)
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- Synthesis of (Z)-1-bromo-1-alkenes and terminal alkynes from anti-2,3-dibromoalkanoic acids by microwave-induced reaction
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(Z)-1-Bromo-1-alkenes were stereoselectively prepared in high yields in a short reaction time by microwave irradiation of the corresponding anti-2,3-dibromoalkanoic acids in a Et3N/DMF system. A one-pot synthesis of terminal alkynes and enynes from 2,3-dibromoalkanoic acids were also developed by microwave-induced reaction.
- Kuang, Chunxiang,Yang, Qing,Senboku, Hisanori,Tokuda, Masao
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p. 4043 - 4052
(2007/10/03)
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- Rapid debromination of vic-dibromoalkanes with zinc powder in acetic acid under microwave irradiation
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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
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p. 282 - 284
(2007/10/03)
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- Gas-solid reactions of single crystals: A study of the reaction of bromine with single crystals of trans-cinnamic acid and a range of its derivatives by infrared and Raman microspectroscopy
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Single crystals of trans-cinnamic acid and of a range of derivatives of this compound containing halogen substituents on the aromatic ring have been reacted with 165 Torr pressure of bromine vapour in a sealed desiccator at 20°C for 1 week. Infrared and Raman microspectroscopic examination of the crystals shows that bromination of the aliphatic double bond, but not of the aromatic ring, has occurred. It is demonstrated also that the reaction is truly gas-solid in nature. A time-dependent study of these reactions shows that they do not follow a smooth diffusion-controlled pathway. Rather the reactions appear to be inhomogeneous and to occur at defects within the crystal. The reaction products are seen to flake from the surface of the crystal. It is shown, therefore, that these are not single crystal to single crystal transitions, as have been observed previously for the photodimerisation of trans-cinnamic acid and several of its derivatives. It is shown that there are no by-products of the reaction and that finely ground samples react to form the same products as single crystals. The Owner Societies 2005.
- Jenkins, Samantha L.,Almond, Matthew J.,Hollins, Peter
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p. 1966 - 1970
(2007/10/03)
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- Esters, amides and substituted derivatives of cinnamic acid: Synthesis, antimicrobial activity and QSAR investigations
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A series of esters (Ia-k), substituted derivatives (II a-d) and amides (IIIa-q) of cinnamic acid were synthesized and evaluated as antibacterial and antifungal agents. All the derivatives belonging to the series I, II and III showed antimicrobial activity comparable to the standard. Compounds If and IIc proved to be the most effective compounds. Quantitative structure-activity relationship (QSAR) investigation with multiple linear regression analysis was applied to find a correlation between different calculated physicochemical parameters of the compounds and biological activity. The quantitative models relating the structural features of cinnamic acid derivatives Ia-k, II a-d and IIIa-q and their antimicrobial activity showed that Gram negative Escherichia coli and Candida albicans (fungus) were the most sensitive microorganisms.
- Narasimhan, Balasubramanian,Belsare, Deepak,Pharande, Devayani,Mourya, Vishnukant,Dhake, Avinash
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p. 827 - 834
(2007/10/03)
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- cis-bromination of encapsulated alkenes
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Inside changes! In striking contrast to the trans-bromination of the free acid, bromination of the bridging cinnamato ligand in 1 proceeds highly diastereoselectively to give the syn-brominated complex 2. A possible explanation for this is that the bromination of 1 proceeds within a confined environment. Since the brominated products can be liberated from the binding pocket of the dinuclear complexes, the metal complexes can be used as reagents for the cis-bromination of olefins with anchoring RCO2- functions.
- Steinfeld, Gunther,Lozan, Vasile,Kersting, Berthold
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p. 2261 - 2263
(2007/10/03)
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- Convenient and stereoselective synthesis of (Z)-1-bromo-1-alkenes by microwave-induced reaction
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(Z)-1-Bromo-1-alkenes were stereoselectively prepared in high yields in a short reaction time (0.2-1.0 min) by microwave irradiation of the corresponding 2,3-dibromoalkanoic acids in DMF in the presence of triethylamine.
- Kuang, Chunxiang,Senboku, Hisanori,Tokuda, Masao
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p. 3893 - 3896
(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 mild procedure for the stereospecific transformation of trans cinnamic acid derivatives to cis β-bromostyrenes
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A new mild procedure has been developed for the synthesis of cis β- bromostyrene analogs with complete Z/E selectivity and good to excellent yields (58.4 - 90.9 %). The process involves carboxyl-halo-elimination of cinnamic acid dibromides by using triethylamine in N,N-dimethylformamide at room temperature. A one-pot procedure has also been described for the direct transformation of cinnamic acids to β-bromostyrenes.
- Kim, Sun Hee,Wei, Han-Xun,Willis, Steven,Li, Guigen
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p. 4179 - 4185
(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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- Mechanistic studies on the formation of phenylpropiolic acid from trans-cinnamic acid
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Mechanistic studies on the formation of phenylpropiolic acid 4 from trans-cinnamic acid 1 by bromination and step-wise dehydrobromination arc reported.
- Dubey, P. K.,Kumar, Ramesh,Grossert, J. S.,Hooper, D. L.
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p. 288 - 293
(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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- Nickel(II) complexes bearing phosphinoaryl oxazoline ligands as pro- catalysts for Grignard cross-coupling
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Ni(II) complexes bearing chiral phosphinoaryl oxazoline ligands are pro- catalysts for cross-coupling of Z-styryl bromide with 1-phenethyl magnesium chloride. Under suitable conditions, there is a dynamic kinetic resolution resulting in moderate enantioselectivity. The nature of the substituent at the stereogenic centre of the oxazoline ligand affects catalysis in two distinct ways: smaller substituents lead to improved rates and selectivities whilst polar substituents reverse the sense of asymmetric induction. The solid state structure of one phosphinoaryl oxazoline Ni(II) pro-catalyst was determined by single crystal x-ray diffraction.
- Lloyd-Jones, Guy C.,Butts, Craig P.
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p. 901 - 914
(2007/10/03)
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- AFM ON CHEMICALLY REACTING CRYSTALS
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A review is given on recent developments of atomic force microscopic (AFM) studies on chemically reacting organic crystals.Three further basic phase transformation mechanisms have been added to the previous five.Both photodimerizations and gas/solid reactions are studied in detail by scanning the surfaces of initial and chemically reacted crystals of anthracenes, thiohydantoines, α- and β-cinnamic acid, and stilbene at different faces, where technically possible.The AFM-features are correlated to known crystal structure data with the aid of semiempirical calculations in part.Thus, detailed molecular mechanisms for the far-reaching well-directed transport phenomena may be derived in most cases and the appearance of the submicroscopic features rationalized.Unimolecular terrace steps of anthracene behave as independent crystal face already.The addition of bromine and chlorine leads to new solid phases directly even though there might be formed mixtures of stereoisomers.If a submicroscopic liquid phase is formed as in the reaction of α-cinnamic acid with chlorine, the surface will be remodelled by the tip and this provides for interesting nanostructures.In many cases there are secondary phase transformations apparently from one form of mixed crystals into another form of mixed crystals either upon continuation of irradiation or just on standing of gas/solid reacted crystals for several hours. - Keywords: atomic force microscopy, solid state photochemistry, gas/solid reaction, basic mechanism, phase transformation, molecular mechanism, unimolecular step, crystal face, crystal structure, nanostructures
- Kaupp, Gerd
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p. 153 - 170
(2007/10/02)
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- Iodide-induced Debromination of Cinnamic Acid and Substituted Cinnamic Acid Dibromides in 2-Methoxyethanol
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The second order rate constants for the iodide-induced debromination of cinnamic acid and substituted cinnamic acid dibromides in 2-methoxyethanol are reported; the reactivities follow the order: p-OCH3 > o-CH3 > p-CH3 > p-NO2 > p-Cl > m-NO2 > -H > m-CH3 > m-OCH3 > o-Cl.The m-CH3 and p-Cl derivatives have higher enthalpies and lower negative entropies of activation whereas methoxy substituted derivatives are characterised by lower enthalpies and higher negative entropies of activation than the unsubstituted acid.The free energy of activation is nearly constant.
- Subramanian, K.,Mathai, I. M.
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p. 909 - 911
(2007/10/02)
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- Elimination from Diastereomeric Methyl 3-Acetoxy-2-halogeno- and 2,3-Dihalogeno-3-phenylpropanoates
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The rates of elimination of a number of erythro- and threo-PhCHYCXHCO2Me in methanolic triethylamine have been measured.The kinetic evidence together with the stereochemical results suggest that elimination of the dihalogeno-compounds occurs by an (E1cB)I process for the erythro-substrates and by a concerted pathways for the threo-isomers.In the case of the acetoxy derivatives the former mechanism seems to be operative for both stereoisomers.
- Cabaleiro, Mercedes C.,Garay, Raul O.
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p. 1473 - 1476
(2007/10/02)
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- UNE NOUVELLE METHODE DE BROMATION : LE TRIBROMURE DE TETRABUTYLAMMONIUM.
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Tetrabutylammonium tribromide (TBA Br3) is used under mild conditions as bromating agent for the addition on double bonds of alkenes and for selective α-substitution of acetals in high yields.
- Fournier, M.,Fournier, F.,Berthelot, J.
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p. 157 - 158
(2007/10/02)
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- REAGENTS AND SYNTHETIC METHODS 38. 4-(DIMETHYLAMINO)PYRIDINIUM BROMIDE PERBROMIDE AS A NEW BROMINATING AGENT FOR ORGANIC COMPOUNDS.
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A new and stable brominating agent for several organic compounds is described.
- Arrieta, A.,Ganboa, I.,Palomo, C.
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p. 939 - 946
(2007/10/02)
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- A CONTRIBUTION TO MECHANISM OF ADDITION OF HYDROGEN BROMIDE TO THE α,β-UNSATURATEDSYSTEM OF 3-PHENYL-2-PROPENOIC ACID
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Rate of addition of hydrogen bromide to meta- and para-substituted 3-phenyl-2-propenoic acids I was followed by polarography and UV spectroscopy.Rate of protonation either is the overall rate determining step or is at least comparable with the rate of the subsequent nucleophile attack.
- Cervinka, Otakar,Kriz, Otomar
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p. 2952 - 2964
(2007/10/02)
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- A CONVENIENT METHOD FOR THE CONVERSION OF trans to cis-CINNAMIC ACIDS
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trans-Cinnamic acids react in sequence with bromine, base, and carbon monoxide to give cis-acids in reasonable yields.
- Galamb, Vilmos,Alper, Howard
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p. 2965 - 2968
(2007/10/02)
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- A Novel Two-phase Chemical Oscillator
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A two-phase oscillator containing cinnamic acid in benzene and lactic acid, ceric sulphate, potassium bromate in 3N H2SO4 aqueous solution is reported.Oscillation characteristics are markedly different for dark and photochemical reactions.
- Rastogi, R. P.,Verma, M. K.
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p. 827 - 829
(2007/10/02)
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