- 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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- A new convenient synthetic route towards 2-(hetero)aryl-substituted thieno[3,2-b]indoles using Fischer indolization
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A number of 2-(hetero)aryl-substituted thieno[3,2-b]indoles have been successfully prepared using an efficient transition-metal-free strategy, involving the Fiesselmann synthesis of methyl 5-(hetero)aryl-3-hydroxythiophene-2-carboxylates from 2-bromo-3-(hetero)arylacrylates and methyl thioglycolate, and the transformation of the synthesized 3-hydroxyesters into the corresponding thiophen-3(2H)-ones, followed by their treatment with arylhydrazines to directly form the targeted structures via Fischer indolization. At the same time, structural variety of the obtained thieno[3,2-b]indoles has been achieved due to a wide range of available starting materials, including both 2-bromo-3-(hetero)arylacrylates and arylhydrazines. In addition, two π-extended molecules, namely 1,4-bis(4H-thieno[3,2-b]indol-2-yl)benzene and 2,5-bis(4H-thieno[3,2-b]indol-2-yl)thiophene, have been synthesized in line with the current approach towards 2-(hetero)arylated thieno[3,2-b]indoles.
- Irgashev, Roman A.,Steparuk, Alexander S.,Rusinov, Gennady L.
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supporting information
p. 4821 - 4832
(2018/07/15)
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- Ru-catalyzed highly chemo- and enantioselective hydrogenation of γ-halo-γ,δ-unsaturated-β-keto esters under neutral conditions
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Finely-tuned ruthenium-catalyzed highly chemoselective and enantioselective hydrogenation of γ-halo-γ,δ-unsaturated-β-keto esters at the carbonyl group was achieved under neutral reaction conditions (ee up to 97%). Both olefin and alkenyl halogen moieties, which are labile under hydrogenation conditions, remained untouched during the reaction.
- Ma, Xin,Li, Wanfang,Li, Xiaoming,Tao, Xiaoming,Fan, Weizheng,Xie, Xiaomin,Ayad, Tahar,Ratovelomanana-Vidal, Virginie,Zhang, Zhaoguo
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supporting information; experimental part
p. 5352 - 5354
(2012/06/30)
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- A substrate-driven approach to determine reactivities of α,β-unsaturated carboxylic esters towards asymmetric bioreduction
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The degree of C=C bond activation in the asymmetric bioreduction of α,β-unsaturated carboxylic esters by ene-reductases was studied, and general recommendations to render these "borderline-substrates" more reactive towards enzymatic reduction are proposed. The concept of "supported substrate activation" was developed. In general, an additional α-halogenated substituent proved to be beneficial for enzymatic activity, whereas β-alkyl or β-aryl substituents were detrimental for the reactivity of nonhalogenated substrates, and α-cyano groups showed little effect. The alcohol moiety of the ester functionality was found to have a strong influence on the reaction rate. Overall, activities were determined by both steric and electronic effects. Biotransformation: The asymmetric bioreduction of α,β-unsaturated carboxylic esters by ene-reductases could be tuned by varying the degree of C=C bond activation (see scheme). An additional α-halogenated substituent proved to be beneficial for enzymatic activity, whereas β-alkyl or β-aryl substituents were detrimental for the reactivity of nonhalogenated substrates. Copyright
- Tasnádi, Gábor,Winkler, Christoph K.,Clay, Dorina,Sultana, Nargis,Fabian, Walter M. F.,Hall, Mélanie,Ditrich, Klaus,Faber, Kurt
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supporting information; experimental part
p. 10362 - 10367
(2012/10/08)
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- Biocatalyzed enantioselective reduction of activated C=C bonds: Synthesis of enantiomerically enriched α-halo-β-arylpropionic acids
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The enantioselective biocatalyzed reduction of the C=C bond of some (Z)-methyl α-halo-β-arylacrylates was investigated. The reaction was performed by baker's yeast fermentation and Old Yellow Enzymes 1-3 mediated biotransformations. The final products wer
- Brenna, Elisabetta,Gatti, Francesco G.,Manfredi, Alessia,Monti, Daniela,Parmeggiani, Fabio
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experimental part
p. 4015 - 4022
(2011/09/15)
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- A novel and convenient protocol for synthesis of a-haloacrylates
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A novel and convenient protocol for synthesis of a-haloacrylates starting from phosphonium ylide and aldedyde or alcohol was described. Halodimethylsulfonium halide was used for the first time in halogenation of phosphonium ylide. Good yield as well as a
- Biao, Jiang,Ying, Dou,Xiangya, Xu,Min, Xu
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p. 593 - 596
(2008/04/12)
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- A thermal cascade route to pyrroloisoindolone and pyrroloimidazolones
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(Chemical Equation Presented) Flash vacuum pyrolysis (FVP) of indol-1-ylacrylate derivatives 11 and 15 or the isomeric indol-3-ylacrylates 21, 22, and 24 at 925°C (0.05 Torr) provides pyrrolo[1,2-a]indol-3-ones 2, 18, 28, and 29 in 53-90% yield by a cascade mechanism that involves a sigmatropic migration, elimination, electrocyclization sequence. Pyrrolo[1,2-a]imidazol-5- ones 3 and pyrrolo[1,2-c]imidazol-5-ones 4 were similarly obtained by FVP of corresponding 2,5-unsubstituted imidazol-1-ylacrylates (e.g., 33), with the former isomer predominating in ca. 80:20 ratio. Migration to the 2-position is therefore favored in the initial sigmatropic shift. FVP of 2-substituted imidazol-1-ylacrylates 35, 37, and 51 (825-875°C) instead give pyrrolo[1,2-c]imidazol-5-ones 56-58 only (88-91%), and that of 4,5-disubstituted imidazol-1-ylacrylates 39 and 41 (825-850°C) provide pyrrolo[1,2-a] imidazol-5-ones 59 and 60 exclusively (93-95%), and thus the selectivity of the initial shift can be controlled by the presence of substituents on the imidazole 2- and 5-positions. FVP of the benzimidazole analogues 61 and 62 at 950°C gave the pyrrolo[1,2-a]benzimidazol-1-ones 6 (71%) and 63 (36%), respectively.
- McNab, Hamish,Tyas, Richard G.
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p. 8760 - 8769
(2008/03/13)
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- Fe(0)-mediated synthesis of tri- and tetra-substituted olefins from carbonyls: An environmentally friendly alternative to Cr(II)
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Fe(0) was investigated as a cost-effective, environmentally friendly alternative to Cr(II) for the olefination of carbonyls by activated polyhalides. In many instances, Fe(0) was equivalent or superior to Cr(II). Notably, Fe(0), but not Cr(II), proved com
- Falck,Bejot, Romain,Barma, Deb K.,Bandyopadhyay, Anish,Joseph, Suju,Mioskowski, Charles
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p. 8178 - 8182
(2007/10/03)
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- Highly selective reaction of α-halo-αβ-unsaturated esters with ketones or aldehydes promoted by SmI2: An efficient alternative access to Baylis-Hillman adducts
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A samarium diiodide promoted addition of aromatic or aliphatic β-substituted-α-halo-α,β-unsaturated esters 1 or 3 to both ketones (in THF) and aldehydes (in acetonitrile) led to (Z)-2-(1-hydroxyalkyl)- 2,3-alkenoates 2 and 4 in good yields and very high stereoselectivity. This method constitutes an efficient and valuable alternative to the synthesis of Baylis-Hillman adducts. A mechanism is proposed to explain this transformation.
- Concellon, Jose M.,Huerta, Monica
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p. 4714 - 4719
(2007/10/03)
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- Versatile Transformations of α,β-Dibromoesters and Ketones in Basic Media under Microwave Irradiation
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Depending on the reaction medium, α,β-dibromoesters under microwave irradiation may selectively lead to α-bromoalk-enes, to alkenes or to (E)-β-bromostyrenes. The corresponding ketones give selectively the α-bromoketones.
- Hamelin, Jack,Saoudi, Aicha,Benhaoua, Hadj
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p. 2185 - 2188
(2007/10/03)
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- A convenient and useful method of preparation of α-bromo enones from the corresponding enones using organic ammonium tribromide (OATB)
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Various acyclic α-bromo enones 2 as well as cyclic α-bromo enones 4 can be prepared from the corresponding acyclic enones 1 and cyclic enones 3 respectively, in a one-pot procedure by employing organic ammonium tribromide, such as cetyltrimethylammonium t
- Bose, Gopal,Bujar Barua, Pankaj M.,Chaudhuri, Mihir K.,Kalita, Dipak,Khan, Abu T.
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p. 290 - 291
(2007/10/03)
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- Bis(2,2,2-trifluoroethyl)bromophosphono-acetate, a novel HWE reagent for the preparation of (E)-α-bromoacrylates: A general and stereoselective method for the synthesis of trisubstituted alkenes
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(Equation presented) A novel reagent, methyl bis(2,2,2-trifluoroethoxy)bromophosphonoacetate (3a), was designed and prepared in order to efficiently synthesize (E)-α-bromoacrylates, which are useful precursors for various C-C bond formations. Honer-Wadswo
- Tago, Keiko,Kogen, Hiroshi
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p. 1975 - 1978
(2007/10/03)
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- A highly stereoselective synthesis of (E)-α-bromoacrylates
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Novel reagent, methyl bis(2,2,2-trifluoroethoxy)bromophosphonoacetate (5a), was designed and prepared in order to efficiently synthesize (E)-α-bromoacrylates 7, from which widely useful precursors for various C-C bond formations were prepared. Horner-Wadsworth-Emmons (HWE) reaction of various aldehydes with 5a in the presence of t-BuOK and 18-C-6 gave corresponding (E)-α-bromoacrylate derivatives with high stereoselectivity and excellent yield. Using the product (E)-α-bromoacrylate 7s as a key intermediate, we succeeded in developing the most effective route of plaunotol synthesis via Suzuki cross-coupling. (C) 2000 Elsevier Science Ltd.
- Tago, Keiko,Kogen, Hiroshi
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p. 8825 - 8831
(2007/10/03)
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- Reaction of bis(sym-collidine)-bromine(I) hexafluorophosphate with α- diazo esters
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Reaction of α-diazo esters with bis(sym-collidine)bromine(I) hexafluorophosphate in methylene chloride at -40°C led to α-bromo-α,β- unsaturated esters.
- Rousseau, Gerard,Marie, Jean-Xavier
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p. 3705 - 3710
(2007/10/03)
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- Elimination reaction over solid supports under microwave irradiation: Synthesis of functionalized alkenes
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Treatment of 1,2-dibromocompounds with KF supported on alumina, or bentonite/E13N under microwave irradiation leads to an elimination reaction which produces functionalized alkenes in fair yields.
- Saoudi, Aicha,Hamelin, Jack,Benhaoua, Hadj
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p. 4035 - 4038
(2007/10/03)
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- A Rapid Synthesis of Aziridine Derivatives over Bentonite in 'Dry Media'
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Functionalized aziridines are synthesized from dibromo compounds and primary aliphatic amines in the absence of solvent over bentonite as a solid support; in some examples microwave activation is compared to normal heating.
- Saoudi, Aicha,Hamelin, Jack,Benhaoua, Hadj
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p. 492 - 493
(2007/10/03)
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- Stereoselective synthesis of (2Z)-α-bromo-α,β-unsaturated esters via arsonium ylide
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(2Z)-α-Bromo-α,β-unsaturated esters 6 can be synthesized stereo-selectively via arsonium ylides in good yields.
- Huang, Zhi-Zhen,Wu, Lu-Ling,Zhu, Liu-Shen,Huang, Xian
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p. 677 - 682
(2007/10/03)
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- Elimination from Diastereoisomeric Methyl 2-Acetoxy-1-bromo- and 1,2-dibromo-2-phenylethylphosphonates
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The examination of the kinetics and stereochemistry of dehydroacetoxylation of erythro- and threo-PhCHOAcCHBrPO3Me2 promoted by triethylamine in various solvents, and comparison with those for erythro- and threo-PhCHOAcCHBrCO2Me, leads to the conclusion that the acetoxybromophosphonates undergo elimination through a carbanion process of the irreversible type.The similarity of the elimination behaviour of the threo-PhCHBrCHBrPO3Me2 and that of threo-PhCHBrCHBrCO2Me is interpreted as indicating that the concerted pathway is also operative for the former compound.In thecase of erythro-PhCHBrCHBrPO3Me2 the kinetics suggest that elimination of the latter occurs via a concerted mechanism.
- Casal, Estela M. G. de,Vuano, Bruno M.,Cabaleiro, Mercedes C.
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p. 121 - 124
(2007/10/02)
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- Dehydroacetoxylation and Acetate Transesterification in the Reactions of erythro- and threo-Methyl 3-(Substituted acetoxy)-2-halogeno-3-phenylpropanoates with Triethylamine
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The response of the rate of triethylamine-induced dehydroacetoxylation of methyl threo-3-acetoxy-2-halogeno-3-phenylpropanoate to the influence of substituents in the leaving group points to a change in mechanism from (E1cB)I to a concerted process of the carbanion type.On the other hand, the erythro-isomers seem to undergo elimination exclusively through a carbanionic pathway.The effect of the acetoxy substituents upon the competitive transesterification is discussed.
- Garay, Raul O.,Cabaleiro, Mercedes C.
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p. 1643 - 1648
(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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- THE AdNSNE MECHANISM IN THE REACTION OF PHENOL AND BENZENETHIOL WITH α-BROMO MICHAEL ACCEPTORS IN THE K2CO3-ACETONE SYSTEM
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In the reaction of α-bromo Michael acceptors with either phenol or benzenethiol formal substitution of the vinylic bromine proceeds through addition of the phenolic reagent, followed by nucleophilic substitution and β-elimination (AdNSNE mechanism) in the system K2CO3-acetone.The process is shown to be stereospecific in the case of 2a,b and 3b,c, leading to the corresponding Z isomer.The reactivity of substrates 1-4 is discussed in terms of their structural features.
- Rosnati, Vittorio,Saba, Antonio,Salimbeni, Aldo,Vettori, Umberto
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p. 249 - 256
(2007/10/02)
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- SOLVENT SHIFTS INDUCED BY DIMETHYLSULPHOXIDE IN α-PROTON MAGNETIC RESONANCES OF CARBONYL COMPOUNDS
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The chemical shifts of α- and β-proton resonances of a number of carbonyl compounds in carbon tetrachloride and dimethylsulphoxide have been determined.The magnitude of the effect of the solvent change on the α-proton resonances seems to vary directly wit
- Cabaliero, M. C.,Giagante, N. N.
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p. 1829 - 1832
(2007/10/02)
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