- Regio- and stereoselective synthesis of bromoalkenes by homolytic hydrobromination of alkynes with hydrogen bromide
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Homolytic hydrobromination of terminal and internal alkynes with a commercially available solution of hydrogen bromide in acetic acid has been investigated for regio- and stereoselective synthesis of bromoalkenes. Under an aerobic atmosphere at room temperature, the reaction of ethynylarenes with a small excess of HBr efficiently gave (2-bromoethenyl)arenes with good to high E-selectivity. (Alk-1-ynyl)arenes, or internal alkynes bearing both phenyl and alkyl groups at the sp-carbons also underwent the air-initiated hydrobromination to exhibit high Z-selectivity under kinetic conditions using a half equivalent of HBr.
- Kumaki, Wataru,Kinoshita, Hidenori,Miura, Katsukiyo
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- Iron(ii)-catalyzed intermolecular aziridination of alkenes employing hydroxylamine derivatives as clean nitrene sources
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The iron-catalyzed intermolecular aziridination of alkenes with hydroxylamine derivatives is described. Using simple iron(ii) sources and readily available ligands, the formal (2 + 1) cycloaddition process proved to be efficient on both styrenes and aliphatic alkenes, providing access to a wide range of aziridines. In these particularly sustainable reaction conditions, yields up to 89% could be obtained, with a catalyst loading which could be lowered to 5 mol% when the reaction was performed on large scale. Preliminary mechanistic studies suggest that both concerted and stepwise pathways are operating in this transformation. This journal is
- Berhal, Farouk,Grimaud, Laurence,Kirby, Georgina,Prestat, Guillaume,Vitale, Maxime R.
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supporting information
p. 9428 - 9432
(2021/12/09)
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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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p. 440 - 446
(2021/01/28)
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- Selective Rhodium-Catalyzed Hydroformylation of Terminal Arylalkynes and Conjugated Enynes to (Poly)enals Enabled by a π-Acceptor Biphosphoramidite Ligand
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The hydroformylation of terminal arylalkynes and enynes offers a straightforward synthetic route to the valuable (poly)enals. However, the hydroformylation of terminal alkynes has remained a long-standing challenge. Herein, an efficient and selective Rh-catalyzed hydroformylation of terminal arylalkynes and conjugated enynes has been achieved by using a new stable biphosphoramidite ligand with strong π-acceptor capacity, which affords various important E-(poly)enals in good yields with excellent chemo- and regioselectivity at low temperatures and low syngas pressures.
- Zhao, Jiangui,Zheng, Xueli,Tao, Shaokun,Zhu, Yuxin,Yi, Jiwei,Tang, Songbai,Li, Ruixiang,Chen, Hua,Fu, Haiyan,Yuan, Maolin
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p. 6067 - 6072
(2021/08/16)
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- Electrochemical Nozaki-Hiyama-Kishi Coupling: Scope, Applications, and Mechanism
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One of the most oft-employed methods for C-C bond formation involving the coupling of vinyl-halides with aldehydes catalyzed by Ni and Cr (Nozaki-Hiyama-Kishi, NHK) has been rendered more practical using an electroreductive manifold. Although early studies pointed to the feasibility of such a process, those precedents were never applied by others due to cumbersome setups and limited scope. Here we show that a carefully optimized electroreductive procedure can enable a more sustainable approach to NHK, even in an asymmetric fashion on highly complex medicinally relevant systems. The e-NHK can even enable non-canonical substrate classes, such as redox-active esters, to participate with low loadings of Cr when conventional chemical techniques fail. A combination of detailed kinetics, cyclic voltammetry, and in situ UV-vis spectroelectrochemistry of these processes illuminates the subtle features of this mechanistically intricate process.
- Baran, Phil S.,Blackmond, Donna G.,Gao, Yang,Hadt, Ryan G.,Hao, Wei,Hill, David E.,McNicholas, Brendon J.,Reisman, Sarah E.,Vantourout, Julien C.
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supporting information
p. 9478 - 9488
(2021/07/19)
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- Iron-Catalyzed Regioselective Alkenylboration of Olefins
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The first examples of an iron-catalyzed three-component synthesis of homoallylic boronates from regioselective union of bis(pinacolato)diboron, an alkenyl halide (bromide, chloride or fluoride), and an olefin are disclosed. Products that bear tertiary or quaternary carbon centers could be generated in up to 87 % yield as single regioisomers with complete retention of the olefin stereochemistry. With cyclopropylidene-containing substrates, ring cleavage leading to trisubstituted E-alkenylboronates were selectively obtained. Mechanistic studies revealed reaction attributes that are distinct from previously reported alkene carboboration pathways.
- Yu, Xiaolong,Zheng, Hongling,Zhao, Haonan,Lee, Boon Chong,Koh, Ming Joo
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supporting information
p. 2104 - 2109
(2020/11/30)
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- Aminium cation-radical catalysed selective hydration of (E)-aryl enynes
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The hydration of carbon-carbon triple bonds is an important and atom economic synthetic transformation. Herein, we report a mild and selective method for the catalytic Markovnikov hydration of (E)-aryl enynes to the corresponding enones, mediated through the bench-stable aminium salt, tris(4-bromophenyl)ammoniumyl hexachloroantimonate (TBPA). The chemoselective and diastereoselective method proceeds under neutral metal-free conditions, delivering excellent product yields from terminal and internal alkyne units. The synthesis of biologically important (E)-3-styrylisocoumarins, including a formal synthesis of the natural product achlisocoumarin III, demonstrates the utility of this novel transformation.
- Giel, Marie-Claire,Barrow, Andrew S.,Smedley, Christopher J.,Lewis, William,Moses, John E.
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supporting information
p. 6991 - 6994
(2021/07/21)
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- Illuminatinganti-hydrozirconation: controlled geometric isomerization of an organometallic species
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A general strategy to enable the formalanti-hydrozirconation of arylacetylenes is reported that mergescis-hydrometallation using the Schwartz Reagent (Cp2ZrHCl) with a subsequent light-mediated geometric isomerization atλ= 400 nm. Mechanistic delineation of thecontra-thermodynamic isomerization step indicates that a minor reaction product functions as an efficientin situgenerated photocatalyst. Coupling of theE-vinyl zirconium species with an alkyne unit generates a conjugated diene: this has been leveraged as a selective energy transfer catalyst to enableE→Zisomerization of an organometallic species. Through anUmpolungmetal-halogen exchange process (Cl, Br, I), synthetically useful vinyl halides can be generated (up toZ?:?E= 90?:?10). This enabling platform provides a strategy to access nucleophilic and electrophilic alkene fragments in both geometric forms from simple arylacetylenes.
- Gilmour, Ryan,Hostmann, Theresa,Nevesely, Tomá?
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p. 10643 - 10648
(2021/08/20)
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- Manganese-catalysed divergent silylation of alkenes
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Transition-metal-catalysed, redox-neutral dehydrosilylation of alkenes is a long-standing challenge in organic synthesis, with current methods suffering from low selectivity and narrow scope. In this study, we report a general and simple method for the manganese-catalysed dehydrosilylation and hydrosilylation of alkenes, with Mn2(CO)10 as a catalyst precursor, by using a ligand-tuned metalloradical reactivity strategy. This enables versatility and controllable selectivity with a 1:1 ratio of alkenes and silanes, and the synthetic robustness and practicality of this method are demonstrated using complex alkenes and light olefins. The selectivity of the reaction has been studied using density functional theory calculations, showing the use of an iPrPNP ligand to favour dehydrosilylation, while a JackiePhos ligand favours hydrosilylation. The reaction is redox-neutral and atom-economical, exhibits a broad substrate scope and excellent functional group tolerance, and is suitable for various synthetic applications on a gram scale. [Figure not available: see fulltext.].
- Dong, Jie,Yuan, Xiang-Ai,Yan, Zhongfei,Mu, Liying,Ma, Junyang,Zhu, Chengjian,Xie, Jin
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p. 182 - 190
(2020/12/17)
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- Method for synthesizing beta-bromostyrene through metal-free catalysis
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The invention discloses a method for synthesizing beta-bromostyrene through metal-free catalysis, and belongs to the technical field of organic chemistry. Substituted styrene 1 is used as a raw material and is reacted in the presence of a bromination reagent, sodium persulfate and dichloroethane, and the beta-bromostyrene compound 2 can be obtained in one step. The method is capable of solving thetechnical problem that in the traditional synthesis method, conversion into alkenyl boron, alkenyl silicon and other intermediates under the catalysis of noble metals and then further halogenation are needed; the defects of expensive reaction reagent, high catalytic cost, complex operation, incapability of large-scale preparation and the like in the traditional preparation method are avoided; byadopting the method, a series of beta-bromostyrene compounds can be obtained, and the method has a potential application prospect.
- -
-
Paragraph 0023-0028; 0031-0033
(2020/02/06)
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- Facile Synthesis of β-Bromostyrenes by Direct Bromination of Styrenes with N -Bromosuccinimide and Sodium Persulfate
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A new, direct, efficient, and transition-metal-free method is reported for the synthesis of β-bromostyrenes from styrenes by using N -bromosuccinimide as the brominating reagent and sodium persulfate (Na 2S 2O 8) as the oxidant. This convenient and concise reaction is practical, operationally simple, and can be adapted for large-scale syntheses.
- Chen, Xuenian,Gao, Yan,Jing, Yi,Ma, Yan-Na,Zhao, Qianyi
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supporting information
(2020/09/09)
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- Electrochemical intramolecular C-H/N-H functionalization for the synthesis of isoxazolidine-fused isoquinolin-1(2: H)-ones
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A general and practical protocol for the construction of isoxazolidine-fused isoquinolin-1(2H)-ones has been described by electrochemical-oxidation-induced intramolecular annulation via amidyl radicals. In an undivided cell, isoquinolinones could be easily generated from various available amides bearing CONHOR groups under metal-free, additive-free and external oxidant-free conditions. Moreover, this transformation proceeded smoothly by using cheap 95% ethanol as the green solvent and could be extended to the gram scale.
- Zhang, Lin-Bao,Geng, Rui-Sen,Wang, Zi-Chen,Ren, Guang-Yi,Wen, Li-Rong,Li, Ming
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supporting information
p. 16 - 21
(2020/01/13)
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- Rhodium-Catalyzed Deoxygenation and Borylation of Ketones: A Combined Experimental and Theoretical Investigation
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The rhodium-catalyzed deoxygenation and borylation of ketones with B2pin2 have been developed, leading to efficient formation of alkenes, vinylboronates, and vinyldiboronates. These reactions feature mild reaction conditions, a broad substrate scope, and excellent functional-group compatibility. Mechanistic studies support that the ketones initially undergo a Rh-catalyzed deoxygenation to give alkenes via boron enolate intermediates, and the subsequent Rh-catalyzed dehydrogenative borylation of alkenes leads to the formation of vinylboronates and diboration products, which is also supported by density functional theory calculations.
- Tao, Lei,Guo, Xueying,Li, Jie,Li, Ruoling,Lin, Zhenyang,Zhao, Wanxiang
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p. 18118 - 18127
(2020/11/26)
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- Zirconium-Catalyzed Synthesis of Alkenylaminoboranes: From a Reliable Preparation of Alkenylboronates to a Direct Stereodivergent Access to Alkenyl Bromides
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A simple procedure has been optimized for the preparation of alkenylaminoborane from alkynes using diisopropylaminoborane and HZrCp2Cl. Coupled with a magnesium-catalyzed dehydrogenation, it allowed for the use of air- and moisture-stable diisopropylamine. This synthesis has been extended to a one-pot sequence leading directly to bromoalkenes with controlled stereochemistry. As such, it provides an easy, scalable, cheap process to access alkenylboronates and both (E)- and (Z)-bromoalkenes from commercially available alkynes.
- Birepinte, Mélodie,Chabaud, Laurent,Liautard, Virginie,Pucheault, Mathieu
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supporting information
p. 2838 - 2843
(2020/04/16)
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- Divergent Synthesis of Vinyl-, Benzyl-, and Borylsilanes: Aryl to Alkyl 1,5-Palladium Migration/Coupling Sequences
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Organosilicon compounds have been extensively utilized both in industry and academia. Studies on the syntheses of diverse organosilanes is highly appealing. Through-space metal/hydrogen shifts allow functionalization of C?H bonds at a remote site, which are otherwise difficult to achieve. However, until now, an aryl to alkyl 1,5-palladium migration process seems to have not been presented. Reported herein is the remote olefination, arylation, and borylation of a methyl group on silicon to access diverse vinyl-, benzyl-, and borylsilanes, constituting a unique C(sp3)?H transformation based on a 1,5-palladium migration process.
- Han, Jie-Lian,Ju, Cheng-Wei,Qin, Ying,Zhao, Dongbing
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supporting information
p. 6555 - 6560
(2020/03/03)
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- Photocatalytic Isomerization of Styrenyl Halides: Stereodivergent Synthesis of Functionalized Alkenes
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An efficient and general method for the isomerization of styrenyl halides under different photocatalytic conditions (fac-Ir(ppy)3 in methanol for E to Z isomerization and fluorescein in 1,4-dioxane for Z to E isomerization, respectively) is disclosed. A series of stereospecific transformations constitute preliminary validation of this strategy in the synthesis of functionalized alkenes, including two diaryl alkenes, a styrenyl boronic ester and an enyne. The photocatalytic isomerization and subsequent cross coupling reaction can be run in a one-pot manner. The stereodivergent synthesis of all four isomers of a conjugated diene, as well as the antitumor agent DMU-212 and its (Z)-isomer highlights the synthetic applicability of this method.
- Zhang, Hao,Xu, Qing,Yu, Lei,Yu, Shouyun
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supporting information
p. 1472 - 1477
(2019/11/03)
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- AgSbF6-Catalyzed: Anti -Markovnikov hydroboration of terminal alkynes
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AgSbF6-Catalyzed anti-Markovnikov addition of pinacolborane (HBpin) to terminal alkynes to produce the E-vinylboronates is reported. This efficient methodology is scalable, compatible with sterically and electronically diverse alkynes, and works at room temperature under solvent-free condition. The utility of this method is demonstrated in the facile synthesis of the clinically important (E)-2,4,3′,5′-tetramethoxystilbene.
- Mamidala, Ramesh,Pandey, Vipin K.,Rit, Arnab
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p. 989 - 992
(2019/01/23)
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- Dual nickel- and photoredox-catalyzed reductive cross-coupling of aryl vinyl halides and unactivated tertiary alkyl bromides
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A novel reductive cross-coupling of aryl vinyl halides and unactivated tertiary alkyl bromides has been realized via photoredox/nickel dual catalysis to produce vinyl arene derivatives bearing all-carbon quaternary centers with excellent E-selectivity. A stoichiometric metal reductant could be avoided by employing commercially available N,N,N′,N′-tetramethylethylenediamine (TMEDA) as the terminal reductant.
- Yu, Weijie,Chen, Long,Tao, Jiasi,Wang, Tao,Fu, Junkai
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p. 5918 - 5921
(2019/05/27)
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- TsNBr2 promoted decarboxylative bromination of α,β-unsaturated carboxylic acids
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A rapid process for decarboxylative bromination of α,β-unsaturated carboxylic acids have been developed using N,N-dibromo-p-toluenesulfonamide (TsNBr2). Treatment of cinnamic acids with TsNBr2 in presence of potassium carbonate in acetonitrile produces corresponding β-bromostyrenes at room temperature. Exclusive formation of (E)-β-bromostyrenes was observed in a stereoselective manner within a very short period of time (5–15 min). This method was further extended for obtaining 1-bromoalkynes from corresponding propiolic acids. Instantaneous formation of bromoalkynes was observed when the reaction was carried out in presence of DBU as a base in acetonitrile at room temperature. A wide variety of cinnamic acids and propiolic acids could be converted to corresponding β-bromostyrenes and 1-bromoalkynes respectively under mild reaction condition with high to excellent yield.
- Hazarika, Debojit,Phukan, Prodeep
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supporting information
p. 4593 - 4596
(2018/11/23)
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- Pd-catalyzed oxidative homo-coupling of acrylates and aromatic alkenes for the conjugated diene synthesis
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We developed a bidentate monoanionic nitrogen ligand that was effective in the Pd-catalyzed oxidative homo-coupling reaction of acrylates and aromatic alkenes. In the presence of Pd(OAc)2/ligand several conjugated dienes were obtained in good yields with high stereoselectivities.
- Zhu, Ting,Li, Zhen,Xiao, Fanhua,Duan, Wei-Liang
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p. 3238 - 3241
(2018/07/21)
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- Palladium-Catalyzed Decarboxylative γ-Olefination of 2,5-Cyclohexadiene-1-carboxylic Acid Derivatives with Vinyl Halides
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This study explores a Pd-catalyzed decarboxylative Heck-type Csp3-Csp2 coupling reaction of 2,5-cyclohexadiene-1-carboxylic acid derivatives with vinyl halides to provide γ-olefination products. The olefinated 1,3-cyclohexadienes can be further oxidized to produce meta-alkylated stilbene derivatives. Additionally, the conjugated diene products can also undergo a Diels-Alder reaction to produce a bicyclo[2.2.2]octadiene framework.
- Chang, Chi-Hao,Chou, Chih-Ming
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supporting information
p. 1949 - 1952
(2018/04/16)
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- Stereoselective Synthesis of Vinyl Iodides through Copper(I)-Catalyzed Finkelstein-Type Halide-Exchange Reaction
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An efficient method for the stereoselective synthesis of vinyl iodides is described. The reactions of vinyl bromides with potassium iodide proceed smoothly in the presence of a copper catalyst under mild reaction conditions to produce the corresponding vinyl iodides stereospecifically and in satisfactory to excellent yields.
- Feng, Xiujuan,Zhang, Haixia,Lu, Wenbo,Yamamoto, Yoshinori,Almansour, Abdulrahman I.,Arumugam, Natarajan,Kumar, Raju Suresh,Bao, Ming
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supporting information
p. 2727 - 2732
(2017/06/13)
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- Nickel-Catalyzed Reductive Cross-Coupling of Vinyl Bromides with Unactivated Alkyl Halides
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The use of pyridine as the sole ligand for the reductive vinylation of unactivated secondary alkyl halides under Ni-catalyzed conditions has been developed. Both alkyl- and aryl-substituted vinyl bromides are suitable, in which alkyl-decorated α-alkenyl bromides resulted in the α-products in good results.
- Gu, Jun,Qiu, Canbin,Lu, Wenbin,Qian, Qun,Lin, Kunhua,Gong, Hegui
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p. 1867 - 1873
(2017/04/06)
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- Decarboxylative bromination of α,β-unsaturated carboxylic acids via an anodic oxidation
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A novel bromination of α,β-unsaturated carboxylic acids was developed via a decarboxylation by virtue of a direct anodic electro-oxidation. In this method, ammonium bromide was employed as a bromine source and the reaction features transition-metal-free, short time, and no additional supporting electrolyte.
- Bi, Mei-Xiang,Qian, Peng,Wang, Yu-Kang,Zha, Zheng-Gen,Wang, Zhi-Yong
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p. 1159 - 1162
(2017/06/19)
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- A stereoselective synthesis of (E)- or (Z)-β-arylvinyl halides via a borylative coupling/halodeborylation protocol
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A new stereoselective method for the synthesis of (E)-β-arylvinyl iodides and (E)- or (Z)-β-arylvinyl bromides from styrenes and vinyl boronates on the basis of a one-pot procedure via borylative coupling/halodeborylation is reported. Depending on the halogenating agent as well as the mode of the halodeborylation reaction, (E) or (Z) isomers are selectively formed.
- Szyling, Jakub,Franczyk, Adrian,Pawlu?, Piotr,Marciniec, Bogdan,Walkowiak, J?drzej
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p. 3207 - 3215
(2017/04/21)
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- Triazole-curcuminoids: A new class of derivatives for 'tuning' curcumin bioactivities?
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Curcumin is a unique blend of pharmacophores responsible for the pleiotropy of this natural pigment. In the present study we have replaced the 1,3-dicarbonyl moiety with a 1,2,3-triazole ring to furnish a new class of triazole-curcuminoids as a possible strategy to generate new compounds with different potency and selectivity compared to curcumin. We obtained a proof-of-principle library of 28 compounds tested for their cytotoxicity (SY-SY5Y and HeLa cells) and for their ability to inhibit NF-κB. Furthermore, we also generated 1,3-dicarbonyl curcuminoids of selected click compounds. Triazole-curcuminoids lost their ability to be Michael's acceptors, yet maintained some of the features of the parent compounds and disclosed new ones. In particular, we found that some compounds were able to inhibit NF-κB without showing cytotoxicity, while others, unlike curcumin, activated NF-κB signalling. This validates the hypothesis that click libraries can be used to investigate the biological activities of curcumin as well as generate analogs with selected features.
- Caprioglio, Diego,Torretta, Simone,Ferrari, Maila,Travelli, Cristina,Grolla, Ambra A.,Condorelli, Fabrizio,Genazzani, Armando A.,Minassi, Alberto
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p. 140 - 152
(2015/12/31)
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- Ohmic Heating and Ionic Liquids in Combination for the Indium-Promoted Synthesis of 1-Halo Alkenyl Compounds: Applications to Pd-Catalysed Cross-Coupling Reactions
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We have explored the combination of ohmic heating (ΩH) with ionic liquids for indium-promoted reactions and report herein the indium-promoted dehalogenation of gem-dibromo alkenes and the indium-mediated reductive elimination of chlorohydrins for the synthesis of 1-halo alkenyl derivatives. Heck, Stille, Suzuki, Kumada and Sonogashira couplings of the resulting 1-halo-1-alkenes with appropriate reagents were carried out to give alkenes, dienes and enynes. We report herein the combination of ohmic heating (ΩH) with ionic liquids for the indium-promoted dehalogenation of gem-dibromo alkenes and the indium-mediated reductive elimination of chlorohydrins. The 1-halo alkenyl derivatives synthesized were then submitted to a series of cross-coupling reactions to give conjugated alkenes, dienes and enynes.
- Soengas, Raquel G.,Silva, Vera L. M.,Pinto, Joana,Rodríguez-Solla, Humberto,Silva, Artur M. S.
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- Metal-Mediated Debromination of gem-Dibromoalkenes under Mild Conditions
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We describe the facile and efficient metal-promoted reduction of C-Br bonds of gem-dibromides. When the reaction is mediated by indium, the corresponding vinyl bromides are obtained in good yields and high E-stereoselectivities. Alternatively, when the reduction is mediated by samarium diiodide, vinyl bromides are obtained in moderate yields and good Z-selectivities.
- Soengas, Raquel G.,Rodríguez-Solla, Humberto,Silva, Artur M.S.
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supporting information
p. 1096 - 1099
(2016/05/19)
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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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- ANTI-HIV COMPOUNDS
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This invention provides, among other things, tetrahydroisoquinolines useful for treating viral infections, pharmaceutical formulations containing such compounds, as well as methods of inhibiting the replication of a virus, such as HIV, or treating a disease, such as AIDS.
- -
-
Paragraph 0300; 0412
(2016/07/05)
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- Tellurium-promoted stereoselective hydrodebromination of 1,1-dibromoalkenes: Synthesis of (: E)-bromoalkenes
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We describe herein an efficient and simple method for the stereoselective hydrodebromination of 1,1-dibromoalkenes by using a catalytic amount of the nucleophilic species of tellurium, generated in situ by the reaction of elemental tellurium with NaBH4. By this methodology, (E)-bromoalkenes were obtained in moderate to excellent yields under mild reaction conditions, without the use of transition metals or base. Furthermore, a high stereoselectivity for the (E)-isomer was observed when 1,1-dibromoarylalkenes were used, thus indicating a promising alternative for future applications in organic synthesis.
- Perin, Gelson,Barcellos, Angelita M.,Peglow, Thiago J.,Nobre, Patrick C.,Cargnelutti, Roberta,Lenard?o, Eder J.,Marini, Francesca,Santi, Claudio
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p. 103657 - 103661
(2016/11/13)
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- Organic photoredox catalysis for the oxidation of silicates: Applications in radical synthesis and dual catalysis
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Metal free photooxidation of alkyl bis(catecholato)silicates with the organic dye 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyano-benzene (4CzIPN) allows the smooth formation of alkyl radicals. The latter can be efficiently engaged either with radical acceptors to provide homolytic addition products or in photoredox/nickel dual catalysis reactions to obtain cross-coupling products.
- Lévêque, Christophe,Chenneberg, Ludwig,Corcé, Vincent,Ollivier, Cyril,Fensterbank, Louis
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supporting information
p. 9877 - 9880
(2016/08/11)
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- A General Copper-Catalyzed Vinylic Halogen Exchange Reaction
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An efficient and general system for the halogen exchange reaction in alkenyl halides has been developed. Upon reaction with catalytic amounts of copper iodide and trans-N,N′-dimethylcyclohexane-1,2-diamine in the presence of tetramethylammonium chloride or bromide, a wide range of easily accessible alkenyl iodides can be smoothly transformed to their far less available chlorinated and brominated derivatives in excellent yields and with full retention of the double bond geometry. This reaction also enables the chlorination of bromoalkenes and could be extended to the use of gem-dibromoalkenes.
- Nitelet, Antoine,Evano, Gwilherm
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supporting information
p. 1904 - 1907
(2016/05/19)
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- Development of a general copper-catalyzed vinylic Finkelstein reaction—application to the synthesis of the C1–C9 fragment of laingolide B
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An efficient and broadly applicable procedure for the copper-catalyzed vinylic Finkelstein reaction is reported. Using a simple, readily available and cheap catalytic system, a broad range of alkenyl iodides and bromides can be smoothly converted to their lower homologues with high yields and full retention of the double bond geometry. Key features of this vinylic Finkelstein reaction are its broad applicability, enabling the conversion of readily available alkenyl iodides to their less available brominated and chlorinated counterparts, and the mild reaction conditions compatible with a range of highly functionalized substrates. The potential of this vinylic halogen exchange reaction in total synthesis and medicinal chemistry was demonstrated by its successful use for the synthesis of the C1–C9 fragment of laingolide B and for the late-stage modification of drug-like molecules. The extension of this halogen exchange to the acetylenic and allenic Finkelstein reactions is also reported.
- Nitelet, Antoine,Jouvin, Kévin,Evano, Gwilherm
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p. 5972 - 5987
(2016/09/16)
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- A Convenient Stereoselective Reduction of Gem-Dibromides with a Combination of Dimethyl Phosphite and Potassium Carbonate
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An efficient and highly stereoselective reduction of a gem-dibromocyclopropane to the corresponding monobromocyclopropane under mild reaction conditions was developed using a combination of dimethyl phosphite and potassium carbonate. This reaction provided a simple and practical way for the synthesis of the valuable monobromocyclopropanes and β-monobromoalkenes.
- Zhao, Yalei,Chen, Tieqiao,Wang, Xiang-Bo,Han, Li-Biao
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p. 1820 - 1827
(2015/12/12)
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- Pd-Catalyzed Difluoromethylation of Vinyl Bromides, Triflates, Tosylates, and Nonaflates
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Pd-catalyzed difluoromethylation of di-, tri- or tetra-substituted vinyl bromides, triflates, tosylates and nonaflates under mild conditions is described. The reaction tolerates a wide range of functional groups, such as bromide, chloride, fluoride, ester, amine, nitrile, and protected carbonyl, thus providing a general route for the preparation of difluoromethylated alkenes. Vinyl fantasy: Pd-catalyzed difluoromethylation of di-, tri-, or tetra-substituted vinyl bromides, triflates, tosylates, and nonaflates under mild conditions is described. The reaction tolerates a wide range of functional groups, such as bromide, chloride, fluoride, ester, amine, nitrile, and protected carbonyl, thus providing a general route for the preparation of difluoromethylated alkenes.
- Chang, Dalu,Gu, Yang,Shen, Qilong
-
supporting information
p. 6074 - 6078
(2015/04/14)
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- Catalytic anti-Markovnikov hydrobromination of alkynes
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We have developed the first catalytic method for anti-Markovnikov hydrobromination of alkynes. The reaction affords terminal E-alkenyl bromides in high yield and with excellent regio- and diastereoselectivity. Both aryl- and alkyl-substituted terminal alkynes can be used as substrates. Furthermore, the reaction conditions are compatible with a wide range of functional groups, including esters, nitriles, epoxides, aryl boronic esters, terminal alkenes, silyl ethers, aryl halides, and alkyl halides. A preliminary study of the reaction mechanism suggests that the hydrobromination reaction involves hydrocupration of an alkyne, followed by the bromination of the alkenyl copper intermediate. This study also suggests that 2-tert-butyl potassium phenoxide functions as a mild catalyst turnover reagent and provides a better understanding of the unique effectiveness of (BrCl2C)2 among brominating reagents.
- Uehling, Mycah R.,Rucker, Richard P.,Lalic, Gojko
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supporting information
p. 8799 - 8803
(2014/07/07)
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- Ni(II) catalyzed bromination of aryl C-H bonds
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Bromination of unactivated aromatic C-H bonds without directing and/or chelating groups was achieved by employing an air stable N-heterocyclic Ni(II) complex. PhI(OAC)2and N-bromosuccinimide have been used as the oxidizing agent and the bromine source, respectively. Yields for bromination are as high as >99%, especially in presence of electron-withdrawing groups like -NO2and -CF3. This is a rare report on C-H bond activation with Ni(II) where, instead of homo C-C coupling, reductive elimination to form C-halogen could be achieved.
- Bhattacharya, Moumita,Cluff, David B.,Das, Siddhartha
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p. 238 - 241
(2015/02/20)
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- Ni(II) catalyzed bromination of aryl C-H bonds
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Bromination of unactivated aromatic C-H bonds without directing and/or chelating groups was achieved by employing an air stable N-heterocyclic Ni(II) complex. PhI(OAC)2 and N-bromosuccinimide have been used as the oxidizing agent and the bromin
- Bhattacharya, Moumita,Cluff, David B.,Das, Siddhartha
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p. 238 - 241
(2014/12/11)
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- H-β-zeolite catalyzed synthesis of β-bromostyrenes from styrene bromohydrins
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Synthesis of β-bromostyrenes from styrene bromohydrins using H-β-zeolite as catalyst under moderate conditions is reported. The catalyst could be regenerated and reused up to three consecutive cycles.
- Pappula, Venkatanarayana,Donthiri, Ramachandra Reddy,Darapaneni, Chandra Mohan,Subbarayappa, Adimurthy
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supporting information
p. 1793 - 1795
(2014/03/21)
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- Diarylrhodates as promising active catalysts for the arylation of vinyl ethers with grignard reagents
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Anionic diarylrhodium complexes, generated by reacting [RhCl(cod)] 2 with 2 equiv of aryl Grignard reagents, were found to be effective active catalysts in cross-coupling reactions of vinyl ethers with aryl Grignard reagents, giving rise to the production of vinyl arenes. In this catalytic system, vinyl-O bonds were preferably cleaved over Ar-O or Ar-Br bonds. A lithium rhodate complex was isolated, and its crystal structure was determined by X-ray crystallography.
- Iwasaki, Takanori,Miyata, Yoshinori,Akimoto, Ryo,Fujii, Yuuki,Kuniyasu, Hitoshi,Kambe, Nobuaki
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supporting information
p. 9260 - 9263
(2014/07/21)
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- Synthesis of perspicamide A and related diverse analogues: Their bioevaluation as potent antileishmanial agents
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The first protocol for the synthesis of perspicamide A and related diverse analogues has been developed from economical and readily available starting materials. Furthermore, a few synthesized analogues, 24a, 24b, 24c, 24d, and 24l, exhibited potent activ
- Pandey, Anand Kumar,Sharma, Rashmi,Shivahare, Rahul,Arora, Ashish,Rastogi, Neeraj,Gupta, Suman,Chauhan, Prem M. S.
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p. 1534 - 1546
(2013/04/10)
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- Nickel(II)-magnesium-catalyzed cross-coupling of 1,1-dibromo-1-alkenes with diphenylphosphine oxide: One-pot synthesis of (E)-1-alkenylphosphine oxides or bisphosphine oxides
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A novel nickel(II)-magnesium-mediated cross-coupling of diphenylphosphine oxide with a variety of 1,1-dibromo-1-alkenes has been developed, which provides a powerful and general methodology for the stereoselective synthesis of various (E)-1-alkenylphosphine oxides or bisphosphine oxides, with operational simplicity of the procedure, good to high yields and broad substrate applicability. Mechanistic studies reveal that the reaction might involve a Hirao reduction, cross-coupling and Michael addition. Copyright
- Liu, Liu,Wang, Yulei,Zeng, Zhiping,Xu, Pengxiang,Gao, Yuxing,Yin, Yingwu,Zhao, Yufen
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supporting information
p. 659 - 666
(2013/04/10)
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- A green hunsdiecker reaction of cinnamic acids
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Tribromo- and trichloroisocyanuric acids react with cinnamic acids in NaOH/H2O/Et2O at room temperature to produce (E)-2-halostyrenes regioselectively in 25-95percent yield. Mechanism studies using Hammett correlations and DFT (density functional theory) calculations have shown that this reaction has as rate determining step the electrophilic addition of chlorine atom to the double bond.
- Sodre?, Leonardo R.,Esteves, Pierre M.,De Mattos, Marcio C. S.
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p. 212 - 218
(2013/05/08)
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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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- On the Origin of E/Z Selectivity in the Modified Julia Olefination - Importance of the Elimination Step
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The mechanism and origin of high E selectivity in the modified Julia olefination of aromatic aldehydes have been explored by computational and experimental means. Reversibility of addition and hence selectivity of the formation of sulfinate 5 is very variable and depends on the nature of the sulfone substrate. However, in all cases, elimination occurs through a concerted antiperiplanar and synperiplanar mechanism for sulfinates anti-5 and syn-5, respectively. Both syn and anti diastereomeric pathways thus lead preferentially to the (E)-alkene. Copyright
- Robiette, Raphael,Pospisil, Jiri
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supporting information
p. 836 - 840
(2013/03/29)
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- Halodeboronation of organotrifluoroborates using tetrabutylammonium tribromide or cesium triiodide
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Halodeboronation of organotrifluoroborates using commercially available tetrabutylammonium tribromide (TBATB) or cesium triiodide in aqueous medium is reported. The mild, transition metal-free method has proven to be tolerant of a wide range of functional groups. High regio- and chemoselectivity are observed. Two synthetic routes to (Z)-dibromoalkenes from alkynes, through stereodefined (Z)-2-bromoalkenyltrifluoroborates and (Z)-1,2-bis(boryl) alkenyltrifluoroborates, have been developed using the TBATB mediated bromodeboronation as the key step.
- Yao, Min-Liang,Kabalka, George W.,Blevins, David W.,Reddy, Marepally Srinivasa,Yong, Li
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experimental part
p. 3738 - 3743
(2012/06/30)
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- Copper-catalyzed direct cross coupling of 1,3,4-oxadiazoles with trans-β-halostyrenes: Synthesis of 2-E-vinyl 1,3,4-oxadiazoles
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The first direct C-H alkenylation of 1,3,4-oxadiazoles with trans-β-halo olefinic system has been carried out using a combination of CuI/DMEDA as a catalyst. A wide range of 2-E-vinyl-substituted oxadiazoles were obtained in high yields (85-93%).
- Das, Biswanath,Reddy, Gandolla Chinna,Balasubramanyam, Penagaluri,Salvanna
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supporting information; experimental part
p. 300 - 305
(2012/01/05)
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- A new entry of highly nucleophilic CHBr3-TiCl4-Mg system for the stereoselective synthesis of 1-alkenyl bromides
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This TiCl4-Mg promoted coupling of CHBr3 with various aldehydes and ketones, especially in sterically hindered or enolizable ketones, provides a simple, practical, and stereoselective carbonyl-bromomethylenation leading primarily to (E)-vinyl bromides.
- Bhorge, Yeshwant Ramchandra,Chang, Su-Haur,Chang, Cheng-Ta,Yan, Tu-Hsin
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experimental part
p. 4846 - 4851
(2012/08/07)
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- Decarboxylative bromination of cinnamic acids by 2-iodoxybenzoic acid with tetrabutylammonium bromide
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The decarboxylative bromination of cinnamic acids using the hypervalent iodine reagent 2-iodoxybenzoic acid with tetrabutylammonium bromide is described, providing good to excellent yields of bromostyrenes. Bromostyrenes are useful coupling components in a wide range of transition metal-catalysed coupling reactions.
- Han, Jianlei,Wei, Yuping
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experimental part
p. 247 - 248
(2012/09/22)
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