The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Choong Eui Song - One of the best experts on this subject based on the ideXlab platform.
-
access to chiral gaba analogues bearing a trifluoromethylated all carbon quaternary stereogenic center through water promoted organocatalytic michael reactions
Organic Letters, 2019Co-Authors: Jae Hun Sim, Jin Hyun Park, Pintu Maity, Choong Eui SongAbstract:Water enables the highly challenging enantioselective Michael addition of sterically congested β-trifluoromethyl-β-aryl- or -alkyl-substituted Nitroolefins with dithiomalonates. Under on-water cond...
-
organocatalytic enantioselective michael addition of malonic acid half thioesters to β Nitroolefins from mimicry of polyketide synthases to scalable synthesis of γ amino acids
ChemInform, 2012Co-Authors: Surajit Some, Myoung Jong Song, Yong Jian Zhang, Choong Eui SongAbstract:The amide (ALK) efficiently promotes the asymmetric coupling of Nitroolefins with the thioester (II) giving adducts of type (III)/(VII) with high enantioselectivity.
-
hydrogen bonding mediated enantioselective organocatalysis in brine significant rate acceleration and enhanced stereoselectivity in enantioselective michael addition reactions of 1 3 dicarbonyls to β Nitroolefins
ChemInform, 2012Co-Authors: Han Yong Bae, Surajit Some, Yong Seop Lee, Choong Eui SongAbstract:Brine provides remarkable rate acceleration and a higher level of stereoselectivity over organic solvents, due to the hydrophobic hydration effect, in the enantioselective Michael addition reactions of 1,3-dicarbonyls to β-Nitroolefins using chiral H-donors as organocatalysts.
-
organocatalytic enantioselective michael addition of malonic acid half thioesters to β Nitroolefins from mimicry of polyketide synthases to scalable synthesis of γ amino acids
Advanced Synthesis & Catalysis, 2011Co-Authors: Han Yong Bae, Surajit Some, Jae Heon Lee, Ju Young Kim, Myoung Jong Song, Sungyul Lee, Yong Jian Zhang, Choong Eui SongAbstract:Highly enantioselective biomimetic Michael addition reactions of malonic acid half thioesters (MAHTs) to a variety of Nitroolefins, affording the optically active γ-amino acid precursors, were developed by employing the Cinchona-based squaramides (up to >99% ee). Remarkably, this biomimetic process is enantioconvergent, a highly desirable feature of a catalytic asymmetric reaction, whereby E/Z-isomers of the Nitroolefins afford the same product enantiomer. The synthetic utility of this organocatalytic protocol was also demonstrated in the formal synthesis of pharmaceutically important γ-amino acids such as baclofen. Moreover, a quantum chemical analysis of the catalyst-substrate complexes is shown to give a detailed and instrumental insight into the origin of the observed catalytic activity.
-
organocatalytic enantioselective michael addition of malonic acid half thioesters to β Nitroolefins from mimicry of polyketide synthases to scalable synthesis of γ amino acids
Advanced Synthesis & Catalysis, 2011Co-Authors: Surajit Some, Myoung Jong Song, Yong Jian Zhang, Choong Eui SongAbstract:Highly enantioselective biomimetic Michael addition reactions of malonic acid half thioesters (MAHTs) to a variety of Nitroolefins, affording the optically active γ-amino acid precursors, were developed by employing the Cinchona-based squaramides (up to >99% ee). Remarkably, this biomimetic process is enantioconvergent, a highly desirable feature of a catalytic asymmetric reaction, whereby E/Z-isomers of the Nitroolefins afford the same product enantiomer. The synthetic utility of this organocatalytic protocol was also demonstrated in the formal synthesis of pharmaceutically important γ-amino acids such as baclofen. Moreover, a quantum chemical analysis of the catalyst-substrate complexes is shown to give a detailed and instrumental insight into the origin of the observed catalytic activity.
Junjun Feng - One of the best experts on this subject based on the ideXlab platform.
-
Enantioselective Vinylogous Michael–Michael Cascade Reactions of 3-Alkylidene Oxindoles and Nitroolefin Enoates
The Journal of organic chemistry, 2017Co-Authors: Junjun FengAbstract:A novel bifunctional squaramide catalyzed vinylogous Michael–Michael cascade reaction of 3-alkylidene oxindoles with Nitroolefin enoates was developed. This convenient, one-pot cascade reaction serves as a powerful tool for the enantioselective construction of potential bioactive chiral chromans, which have three continuous tertiary stereocenters, in moderate to good yields (up to 85%) with excellent stereoselectivities (up to >19:1 dr and >99% ee).
-
enantioselective vinylogous michael michael cascade reactions of 3 alkylidene oxindoles and Nitroolefin enoates
Journal of Organic Chemistry, 2017Co-Authors: Junjun FengAbstract:A novel bifunctional squaramide catalyzed vinylogous Michael–Michael cascade reaction of 3-alkylidene oxindoles with Nitroolefin enoates was developed. This convenient, one-pot cascade reaction serves as a powerful tool for the enantioselective construction of potential bioactive chiral chromans, which have three continuous tertiary stereocenters, in moderate to good yields (up to 85%) with excellent stereoselectivities (up to >19:1 dr and >99% ee).
Kazuo Nagasawa - One of the best experts on this subject based on the ideXlab platform.
-
enantioselective phospha michael reaction of diphenyl phosphonate with Nitroolefins utilizing conformationally flexible guanidinium bisthiourea organocatalyst assembly state tunability in asymmetric organocatalysis
ChemInform, 2012Co-Authors: Yoshihiro Sohtome, Natsuko Horitsugi, Rika Takagi, Kazuo NagasawaAbstract:The organocatalyst (GBT) efficiently promotes the asymmetric addition of the phosphonate (II) to Nitroolefins giving β-nitrophosphonates in high optical purity.
-
enantioselective phospha michael reaction of diphenyl phosphonate with Nitroolefins utilizing conformationally flexible guanidinium bisthiourea organocatalyst assembly state tunability in asymmetric organocatalysis
Advanced Synthesis & Catalysis, 2011Co-Authors: Yoshihiro Sohtome, Natsuko Horitsugi, Rika Takagi, Kazuo NagasawaAbstract:A catalytic enantioselective phospha-Michael reaction of diphenyl phosphonate to Nitroolefins was achieved by utilizing a 1,3-diamine-tethered guanidinium/bisthiourea organocatalyst. The procedure is applicable to Nitroolefins having various aromatic and aliphatic substituents, and enables an efficient access to phospha-Michael products with 90–98% ee. Monomeric or oligomeric active species of the catalyst can be utilized, depending on the presence or absence of water.
Jinpei Cheng - One of the best experts on this subject based on the ideXlab platform.
-
asymmetric michael addition reactions of 3 substituted benzofuran 2 3h ones to Nitroolefins catalyzed by a bifunctional tertiary amine thiourea
ChemInform, 2012Co-Authors: Xiaosong Xue, Bin Wang, Cong Liu, Boxuan Tan, Jialu Jin, Yueyan Zhang, Nan Dong, Jinpei ChengAbstract:Michael reaction of a variety of 3-substituted benzofuranones with β-Nitroolefins proceeds efficiently in the presence of a tertiary amine—thiourea organocatalyst to give benzofuranones bearing an all-carbon quaternary stereocenter at position 3.
-
asymmetric michael addition reactions of 3 substituted benzofuran 2 3h ones to Nitroolefins catalyzed by a bifunctional tertiary amine thiourea
Organic and Biomolecular Chemistry, 2012Co-Authors: Xiaosong Xue, Bin Wang, Cong Liu, Boxuan Tan, Jialu Jin, Yueyan Zhang, Nan Dong, Jinpei ChengAbstract:The current work reports an organocatalytic strategy for the asymmetric catalysis of chiral benzofuran-2(3H)-ones bearing 3-position all-carbon quaternary stereocenters. Accordingly, highly enantioselective Michael addition reactions of 3-substituted benzofuran-2(3H)-ones to Nitroolefins have been developed by utilizing a bifunctional tertiary-amine thiourea catalyst. The reactions accommodate a number of Nitroolefins and 3-substituted benzofuran-2(3H)-ones to give the desired chiral benzofuran-2(3H)-one products with moderate to excellent yields (up to 98%) and moderate to very good selectivities (up to 19 : 1 dr and up to 91% ee). Theoretical calculations using the DFT method on the origin of the stereoselectivity were conducted. The effect of the Nitroolefin substituent position on the stereoselectivity of the Michael addition reaction was also theoretically rationalized.
Yoshiji Takemoto - One of the best experts on this subject based on the ideXlab platform.
-
enantio and diastereoselective michael reaction of 1 3 dicarbonyl compounds to Nitroolefins catalyzed by a bifunctional thiourea
Journal of the American Chemical Society, 2005Co-Authors: Tomotaka Okino, Yasutaka Hoashi, Tomihiro Furukawa, Yoshiji TakemotoAbstract:We synthesized a new class of bifunctional catalysts bearing a thiourea moiety and an amino group on a chiral scaffold. Among them, thiourea 1e bearing 3,5-bis(trifluoromethyl)benzene and dimethylamino groups was revealed to be highly efficient for the asymmetric Michael reaction of 1,3-dicarbonyl compounds to Nitroolefins. Furthermore, we have developed a new synthetic route for (R)-(-)-baclofen and a chiral quaternary carbon center with high enantioselectivity by Michael reaction. In these reactions, we assumed that a thiourea moiety and an amino group of the catalyst activates a Nitroolefin and a 1,3-dicarbonyl compound, respectively, to afford the Michael adduct with high enantio- and diastereoselectivity.
-
enantioselective michael reaction of malonates to Nitroolefins catalyzed by bifunctional organocatalysts
Journal of the American Chemical Society, 2003Co-Authors: Tomotaka Okino, Yasutaka Hoashi, Yoshiji TakemotoAbstract:Michael reaction of malonates to Nitroolefins with chiral bifunctional organocatalysts, bearing both a thiourea and tertiary amino group, afforded Michael adducts with high yields and enantioselectivities (up to 95%, up to 93% ee).