- Reduction of Electron-Deficient Alkenes Enabled by a Photoinduced Hydrogen Atom Transfer
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Direct hydrogen atom transfer from a photoredox-generated Hantzsch ester radical cation to electron-deficient alkenes has enabled the development of an efficient formal hydrogenation under mild, operationally simple conditions. The HAT-driven mechanism is supported by experimental and computational studies. The reaction is applied to a variety of cinnamate derivatives and related structures, irrespective of the presence of electron-donating or electron-withdrawing substituents in the aromatic ring and with good functional group compatibility. (Figure presented.).
- Larionova, Natalia A.,Ondozabal, Jun Miyatake,Cambeiro, Xacobe C.
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supporting information
p. 558 - 564
(2020/12/07)
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- Manganese-catalyzed homogeneous hydrogenation of ketones and conjugate reduction of α,β-unsaturated carboxylic acid derivatives: A chemoselective, robust, and phosphine-free in situ-protocol
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We communicate a user-friendly and glove-box-free catalytic protocol for the manganese-catalyzed hydrogenation of ketones and conjugated C[dbnd]C[sbnd]bonds of esters and nitriles. The respective catalyst is readily assembled in situ from the privileged [Mn(CO)5Br] precursor and cheap 2-picolylamine. The catalytic transformations were performed in the presence of t-BuOK whereby the corresponding hydrogenation products were obtained in good to excellent yields. The described system offers a brisk and atom-efficient access to both secondary alcohols and saturated esters avoiding the use of oxygen-sensitive and expensive phosphine-based ligands.
- Topf, Christoph,Vielhaber, Thomas
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- Rh-catalyzed 1,4-addition reactions of arylboronic acids accelerated by co-immobilized tertiary amine in silica mesopores
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Mesoporous silica-supported Rh complex catalysts were prepared by simple silane-coupling, followed by complexation, and characterized by FT-IR, SEM, Rh K-edge XAFS, and elemental analysis. Local structures of the Rh complexes in each sample were almost similar to those of a nonporous silica-supported diaminorhodium complex. Co-immobilization of a tertiary amine on the same silica surface induced slight changes to the Rh complex structure in the case of the support with smaller pores. The prepared catalysts showed high activity for the 1,4-addition reaction of phenylboronic acids. Co-immobilization of the tertiary amine increased the reaction rate by more than 7-fold, with turnover number of nearly 8500. The catalytic performance achieved with this novel system is with much higher than that reported previously with a nonporous silica-supported catalyst. The mesoporous silica-supported Rh complex-tertiary amine showed a wide substrate scope, including unsaturated ketones and nitriles. This co-immobilized tertiary amine may activate phenylboronic acid to enhance its reactivity in the transmetalation step with Rh-OH species.
- Motokura, Ken,Hashiguchi, Kohei,Maeda, Kyogo,Nambo, Masayuki,Manaka, Yuichi,Chun, Wang-Jae
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- AlCl3 catalyzed coupling of: N-benzylic sulfonamides with 2-substituted cyanoacetates through carbon-nitrogen bond cleavage
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A new cross-coupling reaction of N-benzylic sulfonamides with 2-substituted cyanoacetates for the synthesis of 2-substituted benzylbenzene was reported. In the presence of AlCl3, a broad range of N-benzylic sulfonamides reacted smoothly with 2-substituted cyanoacetates to afford structurally diverse benzylbenzenes in moderate to excellent yields. The conversion could be enlarged to gram-scale efficiently. The practicability of this approach was further manifested in the synthesis of a related bioactive agent with high anti-inflammatory activity.
- Hu, Chen,Hong, Gang,Qian, Xiaofei,Kim, Kwang Rim,Zhu, Xiaoyan,Wang, Limin
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p. 4984 - 4991
(2017/07/10)
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- Conjugate reduction of α,β-unsaturated carbonyl and carboxyl compounds with poly(methylhydrosiloxane) catalyzed by a silica-supported compact phosphane-copper complex
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A silica-supported, cage-type, compact phosphane (Silica-SMAP) was used for the copper-catalyzed conjugate reduction of α,β-unsaturated carbonyl and carboxyl compounds with poly(methylhydrosiloxane) (PMHS). The heterogeneous catalyst system showed high activity and chemoselectivity, and was easily separable from the reaction mixture after the reaction. Furthermore, the catalyst was reusable without loss of its high catalytic activity or selectivity.
- Kawamorita, Soichiro,Yamazaki, Kenji,Ohmiya, Hirohisa,Iwai, Tomohiro,Sawamura, Masaya
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supporting information
p. 3440 - 3444
(2013/02/22)
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- Rhodium-grafted hydrotalcite catalyst for heterogeneous 1,4-addition reaction of organoboron reagents to electron deficient olefins
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A rhodium-grafted hydrotalcite (Rh/HT) was prepared by the treatment of a Mg-Al mixed hydroxide (hydrotalcite, HT) with an aqueous RhCl 3·nH2O solution. The formation of the Rh III species on the HT surface was confirmed by X-ray absorption fine structure spectroscopy. The Rh/HT catalyst was demonstrated to effectively promote the 1,4-addition reaction of organoboron reagents to electron-deficient olefins in both organic and aqueous solvents. The strong surface basicity of HT facilitates the formation of a Rh-OH species, which possesses high nucleophilicity, leading to an efficient transmetalation with organoboron reagents. This catalyst system is also applicable in the one-pot three-component synthesis of 2-cyano-3,3-diphenyl propionate due to the bifunctionality of the Rh/HT surface.
- Motokura, Ken,Hashimoto, Norifumi,Hara, Takayoshi,Mitsudome, Takato,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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experimental part
p. 2416 - 2422
(2011/10/13)
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- A rhodium-grafted hydrotalcite as a highly efficient heterogeneous catalyst for 1,4-addition of organoboron reagents to α,β-unsaturated carbonyl compounds
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Treatment of a hydrotalcite with an aqueous solution of rhodium trichloride results in a Rh-grafted hydrotalcite (Rh/HT) with monomeric Rh species on the surface, which successfully promoted 1,4-addition of organoboron reagents to α,β-unsaturated carbonyl compounds. Furthermore, this catalyst was reusable and was found to be applicable to a one-pot synthesis of 3,3-diarylnitrile.
- Fujita, Noriaki,Motokura, Ken,Mori, Kohsuke,Mizugaki, Tomoo,Ebitani, Kohki,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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p. 5083 - 5087
(2007/10/03)
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- Cyclodimerization of 1,1-dicyanoalkenes and arylidenecyanoacetates promoted by ytterbium diiodide
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The reductive cyclodimerization of 1,1-dicyanoalkenes and arylidenecyanoacetates promoted by Ybl2 has been studied. Functionalized cyclopentenes are obtained in both high yields and stereoselectivity.
- Su,Yang
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p. 163 - 165
(2007/10/03)
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- A hydride transfer reaction from salts of carbanions to activated olefins
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A novel reaction - a β-elimination of a hydride ion from carbanion salts RM (R = Li, MgBr) and R2N-Li+, and its transfer to tetra-substituted activated olefins of the type Ar2C=C(CN)CO2R (R = Me,Et), was studied. Yields of the reduced H--acceptor were used to follow the extent of the H--transfer reaction. A competing Michael addition reaction of RM to the activated olefin also took place. The effects of the solvation properties of the solvent, the reaction temperature, the positive counter-ion, and of various structural features of the H--donor and the H--acceptor, were studied. The structural factors associated with both reactants, played a critically significant role due to the bimolecularity of the reaction. A benzyl substituent at C(β) of RM, a methine-type β-carbon, or a small size of R of RM, resulted in a relatively high extent of the H--transfer reaction. It is suggested that the presently studied β-elimination of a hydride ion takes place by a bimolecular E2cB-type mechanism.
- Feit, Ben-Ami,Shapira, Sarit,Herbst, Amatzya
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p. 317 - 328
(2007/10/02)
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- Asymmetric synthesis of 3,3-diphenyl-2-methylalanine, a new unusual α-amino acid for peptides of biological interest
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A strategy of highly stereoselective enolate trapping of lithium (1S,2R,4R)- 10-dicyclohexylsulfamoylisobornyl-2-cyano-3,3-diphenylpropanoate combined with the appropriate rearrangement process allows the asymmetric synthesis of a novel α-methyl amino aci
- Cativiela,Diaz-De-Villegas,Galvez
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p. 9837 - 9846
(2007/10/02)
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- Arene Hydrides, 10. Michael Additions of Anthracene Hydride. Selective Reduction of the ArC=C Moiety by Fragmentation of the Michael Adduct
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Anthracene hydride (AH-) in THF undergoes Michael addition onto the acrylic acid derivatives 1 and 2.Secondary reactions of the first formed anions 3 and 4 of the Michael adducts depend on the absence (3) or presence (4) of an aryl group in β position.The non-benzylic 3 or its protonated or deprotonated form can cyclize via ester condensation to yield the "dibenzo-bicyclononanones" 10b,c.Deprotonation of the anion 4 by excess AH- usually leads to fragmentation of the C-CAr bond formed in the Michael addition.The overall result is a selective C=C reduction of cinnamonic acid derivatives and analogues: PhR'C=C -> PhR'CH-CH.This fragmentation is hampered in the Michael addition adduct 4h with dimethyl benzylidenemalonate 2h probably due to the necessity of a pronounced conformational reorganization during the fragmentation step.Key Words: Cinnamic acid derivatives, selective saturation / Michael addition / Anthracene hydride
- Sommer, Andreas,Stamm, Helmut
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- A Novel Reduction of Activated Olefins by Lithium Amides
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Activated olefins of the type Ph2C=CXY (X an Y being electronegative substituents) reacted in tetrahydrofuran at low temperature with lithium amides having a hydrogen atom at C-α, to give the corresponding saturated derivatives.The reduction took place by
- Melamed, Uri,Feit, Ben-Ami
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p. 1267 - 1269
(2007/10/02)
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