The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Eric Meggers - One of the best experts on this subject based on the ideXlab platform.
-
visible light activated catalytic enantioselective β alkylation of α β unsaturated 2 acyl imidazoles using hantzsch esters as radical reservoirs
Journal of Organic Chemistry, 2018Co-Authors: Xiaoqiang Huang, Francisco F De Assis, Midori Akiyama, Ronaldo A Pilli, Eric MeggersAbstract:An efficient and practical method for the enantioselective β-functionalization of α,β-unsaturated 2-acyl imidazoles is described. The method uses a previously devised chiral-at-metal Rhodium catalyst (Λ-RhS, 4 mol %) along with Hantzsch ester derivatives as alkyl radical sources. The Rhodium Complex exerts a dual role as the visible-light-absorbing unit upon substrate binding and as the asymmetric catalyst. The method provides up to quantitative yields with excellent enantioselectivities up to 98% ee and can be classified as a redox-neutral, electron-transfer-catalyzed reaction.
-
direct visible light excited asymmetric lewis acid catalysis of intermolecular 2 2 photocycloadditions
Journal of the American Chemical Society, 2017Co-Authors: Xiaoqiang Huang, Taylor R Quinn, Klaus Harms, Richard D Webster, Lilu Zhang, Olaf Wiest, Eric MeggersAbstract:A reaction design is reported in which a substrate-bound chiral Lewis acid Complex absorbs visible light and generates an excited state that directly reacts with a cosubstrate in a highly stereocontrolled fashion. Specifically, a chiral Rhodium Complex catalyzes visible-light-activated intermolecular [2+2] cycloadditions, providing a wide range of cyclobutanes with up to >99% ee and up to >20:1 d.r. Noteworthy is the ability to create vicinal all-carbon-quaternary stereocenters including spiro centers in an intermolecular fashion.
-
asymmetric dual catalysis via fragmentation of a single Rhodium precursor Complex
ChemInform, 2016Co-Authors: Liangliang Song, Eric Meggers, Lei GongAbstract:A strategy for dual transition metal catalysis and organocatalysis is reported via the in situ disintegration of a single Rhodium Complex. The hereby generated chiral Lewis acid and L-β-phenylalanine synergistically catalyze the Michael addition of α,α-disubstituted aldehydes to α,β-unsaturated 2-acyl imidazoles under the formation of vicinal quaternary/tertiary stereocenters. Conveniently, the chiral-at-metal Rhodium catalyst can be synthesized in just two steps starting from Rhodium trichloride without the need for any chromatography.
Qiang Kang - One of the best experts on this subject based on the ideXlab platform.
-
asymmetric 3 2 cycloaddition employing n n cyclic azomethine imines catalyzed by chiral at metal Rhodium Complex
Organic Letters, 2018Co-Authors: Jun Gong, Qian Wan, Qiang KangAbstract:An efficient asymmetric 1,3-dipolar cycloaddition of α,β-unsaturated 2-acyl imidazoles with N,N′-cyclic azomethine imines catalyzed by a chiral-at-metal Rhodium Complex is reported. The corresponding N,N′-bicyclic pyrazolidine derivatives with three contiguous tertiary stereocenters were obtained in good yields (up to 99%) with excellent stereoselectivities (>20:1 dr and >99% ee). Remarkably, as little as 0.5 mol % of a chiral Rh(III) Complex can promote a gram-scale reaction with excellent yield and enantioselectivity.
-
chiral at metal rh iii Complex catalyzed michael addition of pyrazolones with α β unsaturated 2 acyl imidazoles
Organic Letters, 2018Co-Authors: Qian Wan, Qiang KangAbstract:An efficient enantioselective conjugate addition of pyrazolones with α,β-unsaturated 2-acyl imidazoles catalyzed by chiral-at-metal Rhodium Complex is reported. The corresponding adducts were obtained in good yields (85%-96%) with excellent enantioselectivities (up to >99%). This protocol exhibits extraordinary reactivity, because of the fact that a Complex with as little as 0.05 mol % Rh(III) can catalyze the title reaction on a gram-scale with excellent enantioselectivity.
-
a visible light activated Rhodium Complex in enantioselective conjugate addition of α amino radicals with michael acceptors
Chemical Communications, 2017Co-Authors: Shaoxia Lin, Guijun Sun, Qiang KangAbstract:We report an efficient enantioselective conjugate addition of photogenerated α-amino radicals to Michael acceptors catalyzed by a newly prepared chiral-at-metal Rhodium Complex. This protocol shows that a single Rh(III) Complex can serve not only as a Lewis acid but also as a photoredox catalyst to control the stereoselectivity during the bond formation.
Jingen Deng - One of the best experts on this subject based on the ideXlab platform.
-
chiral surfactant type catalyst enantioselective reduction of long chain aliphatic ketoesters in water
ChemInform, 2015Co-Authors: Zechao Lin, Jin Zhu, Qingfei Huang, Qiuya Huang, Qiwei Wang, Lei Tang, Deying Gong, Jun Yang, Jingen DengAbstract:A Rhodium Complex with an amphiphilic, chiral surfactant-type ligand is applied to the asymmetric transfer hydrogenation of long-chained aliphatic ketoesters.
-
synthesis of a water soluble cationic chiral diamine ligand bearing a diguanidinium and application in asymmetric transfer hydrogenation
Tetrahedron-asymmetry, 2011Co-Authors: Yuanfu Tang, Jingen Deng, Xuefeng Li, Chunxia LianAbstract:Abstract A novel water-soluble cationic N -monosulfonated chiral diamine ligand diguanidinium 1c was easily prepared from ( R , R )-DPEN and its Rhodium Complex and was successfully applied in the asymmetric transfer hydrogenation of prochiral ketones and imines in water by using sodium formate and formic acid as co-hydrogen donors. Various substrates were reduced with high yields and good to excellent enantioselectivities (up to >99% ee).
-
chemoselective and enantioselective transfer hydrogenation of β β disubstituted nitroalkenes catalyzed by a water insoluble chiral diamine Rhodium Complex in water
Tetrahedron-asymmetry, 2010Co-Authors: Yuanfu Tang, Jing Xiang, Linfeng Cun, Yuqin Wang, Jin Zhu, Jian Liao, Jingen DengAbstract:Abstract Asymmetric transfer hydrogenation of β,β-disubstituted nitroalkenes catalyzed by a chiral diamine–Rhodium Complex in combination with HCO 2 Na–HCO 2 H as a hydrogen source in water was successfully realized with high reactivity, excellent chemoselectivity and good enantioselectivity. The metal precursor and pH value of the aqueous solution have a large influence on the reactivity and chemoselectivity. The substituents on the benzene rings and the sulfonyl groups of TsDPEN have significant effects on the enantioselectivity. This catalytic asymmetric transformation is one of the most practical pathways to obtain optically active nitroalkanes.
Francisco F De Assis - One of the best experts on this subject based on the ideXlab platform.
-
visible light activated catalytic enantioselective β alkylation of α β unsaturated 2 acyl imidazoles using hantzsch esters as radical reservoirs
Journal of Organic Chemistry, 2018Co-Authors: Xiaoqiang Huang, Francisco F De Assis, Midori Akiyama, Ronaldo A Pilli, Eric MeggersAbstract:An efficient and practical method for the enantioselective β-functionalization of α,β-unsaturated 2-acyl imidazoles is described. The method uses a previously devised chiral-at-metal Rhodium catalyst (Λ-RhS, 4 mol %) along with Hantzsch ester derivatives as alkyl radical sources. The Rhodium Complex exerts a dual role as the visible-light-absorbing unit upon substrate binding and as the asymmetric catalyst. The method provides up to quantitative yields with excellent enantioselectivities up to 98% ee and can be classified as a redox-neutral, electron-transfer-catalyzed reaction.
Xiaoqiang Huang - One of the best experts on this subject based on the ideXlab platform.
-
visible light activated catalytic enantioselective β alkylation of α β unsaturated 2 acyl imidazoles using hantzsch esters as radical reservoirs
Journal of Organic Chemistry, 2018Co-Authors: Xiaoqiang Huang, Francisco F De Assis, Midori Akiyama, Ronaldo A Pilli, Eric MeggersAbstract:An efficient and practical method for the enantioselective β-functionalization of α,β-unsaturated 2-acyl imidazoles is described. The method uses a previously devised chiral-at-metal Rhodium catalyst (Λ-RhS, 4 mol %) along with Hantzsch ester derivatives as alkyl radical sources. The Rhodium Complex exerts a dual role as the visible-light-absorbing unit upon substrate binding and as the asymmetric catalyst. The method provides up to quantitative yields with excellent enantioselectivities up to 98% ee and can be classified as a redox-neutral, electron-transfer-catalyzed reaction.
-
direct visible light excited asymmetric lewis acid catalysis of intermolecular 2 2 photocycloadditions
Journal of the American Chemical Society, 2017Co-Authors: Xiaoqiang Huang, Taylor R Quinn, Klaus Harms, Richard D Webster, Lilu Zhang, Olaf Wiest, Eric MeggersAbstract:A reaction design is reported in which a substrate-bound chiral Lewis acid Complex absorbs visible light and generates an excited state that directly reacts with a cosubstrate in a highly stereocontrolled fashion. Specifically, a chiral Rhodium Complex catalyzes visible-light-activated intermolecular [2+2] cycloadditions, providing a wide range of cyclobutanes with up to >99% ee and up to >20:1 d.r. Noteworthy is the ability to create vicinal all-carbon-quaternary stereocenters including spiro centers in an intermolecular fashion.