- Iron-Catalyzed Photoredox Functionalization of Methane and Heavier Gaseous Alkanes: Scope, Kinetics, and Computational Studies
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Herein, we report the development of the photocatalytic C-H functionalization of methane, ethane, and heavier gaseous alkanes with good yields and selectivity, broad scope (57 examples), mild conditions, and low cost. Kinetics and density functional theor
- Zhang, Qingqing,Liu, Shuyang,Lei, Jinglan,Zhang, Yongqiang,Meng, Changgong,Duan, Chunying,Jin, Yunhe
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p. 1901 - 1906
(2022/03/27)
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- Hydrofluoromethylation of alkenes with fluoroiodomethane and beyond
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A process for the direct hydrofluoromethylation of alkenes is reported for the first time. This straighforward silyl radical-mediated reaction utilises CH2FI as a non-ozone depleting reagent, traditionally used in electrophilic, nucleophilic and carbene-type chemistry, but not as a CH2F radical source. By circumventing the challenges associated with the high reduction potential of CH2FI being closer to CH3I than CF3I, and harnessing instead the favourable bond dissociation energy of the C-I bond, we demonstrate that feedstock electron-deficient alkenes are converted into products resulting from net hydrofluoromethylation with the intervention of (Me3Si)3SiH under blue LED activation. This deceptively simple yet powerful methodology was extended to a range of (halo)methyl radical precursors including ICH2I, ICH2Br, ICH2Cl, and CHBr2F, as well as CH3I itself; this latter reagent therefore enables direct hydromethylation. This versatile chemistry was applied to18F-,13C-, and D-labelled reagents as well as complex biologically relevant alkenes, providing facile access to more than fifty products for applications in medicinal chemistry and positron emission tomography.
- Chen, Xuanxiao,Gouverneur, Véronique,Hell, Sandrine M.,Meyer, Claudio F.,Ortalli, Sebastiano,Sap, Jeroen B. I.
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p. 12149 - 12155
(2021/09/28)
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- Photocatalytic Giese-Type Reaction with Alkylsilicates Bearing C,O-Bidentate Ligands
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Herein, a photocatalytic Giese-type reaction with alkylsilicates bearing C,O-bidentate ligands as stable alkyl radical precursors has been reported. The alkylsilicates were prepared in one step from organometallic reagents. Not only primary, secondary, and tertiary alkyl radicals, but also elusive methyl radicals, could be generated by using the present reaction system. The generated radicals were trapped by electron-deficient olefins bearing various functional groups to give the desired alkyl adducts. The silicon byproduct can be recovered after the photoreaction. The radical generation process was investigated by theoretical calculations, which provided an insight into the facile generation of methyl radicals from methylsilicate bearing C,O-bidentate ligands.
- Morofuji, Tatsuya,Matsui, Yu,Ohno, Misa,Ikarashi, Gun,Kano, Naokazu
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supporting information
p. 6713 - 6718
(2021/02/26)
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- C(sp3)-H functionalizations of light hydrocarbons using decatungstate photocatalysis in flow
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Direct activation of gaseous hydrocarbons remains a major challenge for the chemistry community. Because of the intrinsic inertness of these compounds, harsh reaction conditions are typically required to enable C(sp3)-H bond cleavage, barring potential applications in synthetic organic chemistry. Here, we report a general and mild strategy to activate C(sp3)-H bonds in methane, ethane, propane, and isobutane through hydrogen atom transfer using inexpensive decatungstate as photocatalyst at room temperature. The corresponding carbon-centered radicals can be effectively trapped by a variety of Michael acceptors, leading to the corresponding hydroalkylated adducts in good isolated yields and high selectivity (38 examples).
- Deng, Yuchao,Fagnoni, Maurizio,Guthrie, Duncan,Laudadio, Gabriele,No?l, Timothy,Nun?, Manuel,Ravelli, Davide,Sun, Yuhan,Wal, Klaas Van Der
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- Rh-catalyzed one-pot reductive alkylation of malononitrile under transfer hydrogenation conditions
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Efficient synthesis of monosubstituted malononitriles was achieved by one-pot reductive alkylation of malononitrile with carbonyl compounds via [Cp*RhCl2]2-catalyzed transfer hydrogenation reaction.
- Wu, Jiashou,Jiang, Huajiang
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experimental part
p. 1218 - 1226
(2011/05/04)
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- Homogeneous hydrogenation of electron-deficient alkenes by iridium complexes
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The catalytic homogeneous hydrogenation of electron-deficient alkenes (nucleophilic hydrogenation) was achieved in the presence of iridium complexes and a base as co-catalyst. Contrary to hydrogenation of electron-rich alkenes, which is inactivated by bases, the hydrogenation of the electron-deficient alkenes turned out to be base activated. Here, we present a more thorough study on the capacities but also limitations of this new reaction mechanism using screenings of the reaction conditions as well as different Ir complexes and substrates. The formation of a catalytically active Ir complex is proposed. The active complex usually attacks a soft electron-deficient atom, if more than one possibility exists (as shown by density functional theory computations). Additionally, first examples of enantiomeric enrichments in the presence of chiral Ir complexes are presented. The high catalyst load needed and the moderate yields show that the active complex is very unstable under conditions of nucleophilic hydrogenation and is quickly deactivated, which has to be addressed in further studies. Copyright
- Semeniuchenko, Volodymyr,Exner, Thomas E.,Khilya, Volodymyr,Groth, Ulrich
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experimental part
p. 804 - 809
(2012/03/26)
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- Polymer-supported hantzsch 1,4-dihydropyridine ester: An efficient biomimetic hydrogen source for the reduction of ketimines and electron-withdrawing group conjugated olefins
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A polymer-supported Hantzsch 1,4-dihydropyridine ester was observed to be a useful selective reducing agent for the reduction of ketimines and electron-withdrawing conjugated olefins. The rate of the reduction of electron-withdrawing conjugated olefins is dependent on the nature of the conjugated substituents and could be enhanced by microwave irradiation. The reduction of (Z)-α-cyano-β-bromomethylcinnamates to cyclopropane derivatives using polymer-supported Hantzsch 1,4-dihydropyridine ester was found to proceed stereoselectively and in good yields.
- Che, Jun,Lam, Yulin
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experimental part
p. 1752 - 1758
(2010/09/11)
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- Nucleophilic homogeneous hydrogenation by iridium complexes
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Catalytic homogeneous hydrogenation of 7-methoxy-3-phenylchromone and other substrates was achieved in the presence of cationic iridium complexes and base as co-catalyst. Contrary to common alkene hydrogenation, which is inactivated by base, the hydrogena
- Semeniuchenko, Volodymyr,Khily, Volodymyr,Groth, Ulrich
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experimental part
p. 271 - 275
(2009/07/11)
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- Monosubstituted malononitriles: Efficient one-pot reductive alkylations of malononitrile with aromatic aldehydes
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A powerful new one-pot method has been developed for the reductive alkylation of malononitrile with aromatic aldehydes. This new procedure has vastly improved the yield and efficiency of the process, and increased the scope of the aromatic aldehydes. Inco
- Tayyari, Fariba,Wood, Dwight E.,Fanwick, Phillip E.,Sammelson, Robert E.
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p. 279 - 285
(2008/12/22)
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- Sodium borohydride as the only reagent for the efficient reductive alkylation of malononitrile with ketones and aldehydes
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An efficient and convenient method for the synthesis of primary and secondary monosubstituted malononitriles has been developed. In this method, sodium borohydride in isopropanol has a catalytic effect on the initial condensation between malononitrile and
- Dunham, Jason C.,Richardson, Adam D.,Sammelson, Robert E.
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p. 680 - 686
(2007/10/03)
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- Transfer hydrogenation of activated C=C bonds catalyzed by ruthenium amido complexes: Reaction scope, limitation, and enantioselectivity
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(Chemical Equation Presented) It was found that the chemoselectivity could be completely switched from C=O to C=C bonds in the transfer hydrogenation of activated α,β-unsaturated ketones catalyzed by diamine-ruthenium complex. Moreover, this addition via metal hydride had been applied to the reduction of various activated olefins. The electron-withdrawing ability of functional groups substituted on C=C bonds at the α- or β-position had strong influence on the reactivity. In addition, a wide variety of chiral diamine-Ru(II)-(arene) systems was investigated to explore the asymmetric transfer hydrogenation of prochiral α,α-dicyanoolefins. Two parameters had been systematically studied, (i) the structure of the N-sulfonylated chiral diamine ligands, in which several chiral diamines substituted on the benzene ring of DPEN were first reported, and (ii) the structure of the metal precursors, and high enantioselectivitiy (up to 89% ee) at the β-carbon was obtained.
- Xue, Dong,Chen, Ying-Chun,Cui, Xin,Wang, Qi-Wei,Zhu, Jin,Deng, Jin-Gen
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p. 3584 - 3591
(2007/10/03)
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- A convenient and selective one-pot method for the synthesis of monosubstituted secondary alkyl malononitriles
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We have found that α,α-dicyanoalkenes can be efficiently and selectively reduced to α,α-dicyanoalkanes (malononitriles) with NaBH4 in 95% EtOH at 0 °C. In addition, we have determined that the condensation of malononitrile with ketones using absorption alumina as a catalyst can be followed directly, in one pot, by reduction with NaBH 4 in 95% EtOH at 0 °C to provide the monosubstituted secondary alkyl malononitriles in good to excellent yields (42-94%). This procedure provides a convenient alternative to direct alkylation of malononitrile or reduction of α,α-dicyanoalkene intermediates.
- Sammelson, Robert E.,Allen, Mark J.
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p. 543 - 546
(2007/10/03)
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- A new and effective method for providing optically active monosubstituted malononitriles: Selective reduction of α,β-unsaturated dinitriles catalyzed by copper hydride complexes
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A copper hydride complex, which was generated in situ from CuOt-Bu, BINAP, and PhSiH3, was found to be a highly effective catalyst for the reduction of the CC of α,β-unsaturated dinitriles. In addition to CuOt-Bu, some air and moisture stable C
- Ren, Yunlai,Xu, Xianlun,Sun, Kunpeng,Xu, Jian
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p. 4010 - 4014
(2007/10/03)
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- Reduction of activated conjugated alkenes by the InCl3-NaBH 4 reagent system
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A combination of a catalytic amount of indium (III) chloride and sodium borohydride in acetonitrile reduces selectively the carbon-carbon double bonds in conjugated alkenes such as α,α-dicyano olefins, α,β-unsaturated nitriles, cyanoesters, cyanophosphonate and dicarboxylic esters. However, reduction of chalcones is little different. They are reduced to a mixture of saturated ketones and alcohols if the reaction mixture is quenched with H2O, whereas quenching with MeOH leads to saturated alcohols only.
- Ranu, Brindaban C.,Samanta, Sampak
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p. 7901 - 7906
(2007/10/03)
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- Use of indium hydride (Cl2InH) for chemoselective reduction of the carbon-carbon double bond in conjugated alkenes
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Indium hydride (Cl2InH) generated in situ from a combination of a catalytic amount of indium(III) chloride and sodium borohydride selectively reduces the carbon-carbon double bond in conjugated alkenes such as α,α-dicyano olefins, α,β-unsaturated nitriles, cyano esters, cyanophosphonate, diesters and ketones.
- Ranu, Brindaban C.,Samanta, Sampak
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p. 7405 - 7407
(2007/10/03)
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- Direct addition of Zr-C bonds of alkylzirconocenes to activated alkenes
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Direct addition of alkylzirconocenes to activated alkenes was found, for the first time. Octyl- and decylzirconocene chloride reacted with benzylidenemalononitrile to give the corresponding addition products after hydrolysis in 86% and 79% yield, respecti
- Liu, Yuanhong,Shen, Baojian,Kotora, Martin,Nakajima, Kiyohiko,Takahashi, Tamotsu
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p. 7019 - 7028
(2007/10/03)
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- Indium metal as a reducing agent. Selective reduction of the carbon-carbon double bond in highly activated conjugated alkenes
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(Equation presented) Indium metal in aqueous ethanolic ammonium chloride reduces the C=C bond in highly activated conjugated alkenes such as α,α-dicyano olefins, β-arylenones, and enone esters.
- Ranu, Brindaban C.,Dutta, Jyotirmoy,Guchhait, Sankar K.
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p. 2603 - 2605
(2007/10/03)
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- Photochemical carbon-silicon bond forming reaction on electron-deficient alkenes by disilanes and polysilanes via photoinduced electron transfer
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The phenanthrene-sensitized photoreaction of electron-deficient alkenes with disilanes in acetonitrile gave silylated alkanes in high yields.The photosilylation occurred in a highly regioselective manner at the position β to the electron-withdrawing group
- Mizuno, Kazuhiko,Nakanishi, Kazuhisa,Chosa, Jun-ichi,Otsuji, Yoshio
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- Lewis Acid-prompted Conjugate Reduction of α,β-Unsaturated Carbonyl Compounds by 2-Phenylbenzothiazoline (2-Phenyl-2,3-dihydrobenzothiazole)
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Reduction of various α,β-unsaturated ketones (3a-g) and (4a-d) in methanol by the benzothiazoline (1) in the presence of aluminium chloride gives, in all cases, the corresponding saturated ketones (5a-g) and (6a-d)without any of the unsaturated or saturated alcohol.Reduction of α,β-unsaturated esters (7a,b) similarly gives the saturated esters (9a,b), while reaction of cinnamaldehyde (8) with compound (1) does not occur at all.Among the Lewis acids examined, aluminium chloride gives the best results.Reduction of 2'-azachalcone (21) with 2-phenylbenzothiazoline reveals that, in the reduction product, the deuterium atom is located at the β-position with respect to the carbonyl group.The result obtained from the reduction of the same substrate with compound (1) in methanol shows that no incorporation of a hydrogen atom from the solvent takes place and suggests (indirectly) that the introduced hydrogen atom at the α-position of the product comes from the benzothiazoline (1).The reaction of (Z)-1,2-dibenzoyl-1,2-diphenylethylene (30) with compound (1) in the presence of aluminium chloride stereospecifically yields meso-1,2-dibenzoyl-1,2-diphenylethane (31).This shows that the transfer of two hydrogens from compound (1) to the carbon-carbon double bond of the enone proceeds via cis-addition.Experiments with ethyl phenylpropiolate (28) also support cis-reduction for the present conjugate reduction.These results are interpreted in terms of a mechanism involving synchronous transport of a pair of hydrogens from the benzothiazoline (1); i.e a cyclic addition of the two hydrogens either in exact or nearly exact concurrence.
- Chikashita, Hidenori,Miyazaki, Makoto,Itoh, Kazuyoshi
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p. 699 - 706
(2007/10/02)
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- In Situ Generation and Synthetic Application of 2-Phenylbenzimidazoline to the Selective Reduction of Carbon-Carbon Double Bonds of Electron-Deficient Olefins
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2-Phenylbenzimidazoline (PBI) as a mild, selective, and convenient reducing agent was efficiently generated in situ from o-phenylenediamine and benzaldehyde in alcohols.A generally applicable method for the selective reduction of carbon-carbon double bonds of a variety of electron-deficient olefins with an alcoholic solution of PBI is described.The reduction of α,β-unsaturated ketones to the corresponding saturated ketones could also be accomplished (but, less effectively) with PBI with the aid of a Lewis-acid catalyst. 1-Methyl-2-(o-nitrophenyl)benzimidazoline prepared and isolated by the reaction of o-nitrobenzaldehyde with N-methyl-o-phenylenediamine reduced benzylidenemalononitrile to give benzylmalononitrile and 1-methyl-2-(o-nitrophenyl)benzimidazoline in high yields.This shows the validity of PBI to be the actual reducing species in the present reduction system.From a mechanistic study, the present reductions could be interpreted in terms of a mechanism involving a synchronous transport of a pair of hydrogens or a sequential transfer of a hydride and a proton from PBI to the olefins.
- Chikashita, Hidenori,Nishida, Shuichi,Miyazaki, Makoto,Morita, Yasuhiro,Itoh, Kazuyoshi
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p. 737 - 746
(2007/10/02)
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