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Chizuko Kabuto

Other affiliations: Yamagata University, Shinshu University, Kyoto University  ...read more
Bio: Chizuko Kabuto is an academic researcher from Tohoku University. The author has contributed to research in topics: Crystal structure & Trimethylsilyl. The author has an hindex of 47, co-authored 383 publications receiving 7953 citations. Previous affiliations of Chizuko Kabuto include Yamagata University & Shinshu University.


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TL;DR: In this paper, the authors used diimide prepared in situ from p-toluenesulfonyl hydrazide in diglyme for the synthesis of saturated 12-and 18-membered oligosilacycloalkanes.
Abstract: The hydrogenation of bistrimethylsilylactylene, bis(trimethylsilyl)-1,3-diynes, and related silylalkynes giving the corresponding saturated compounds were achieved by using diimide prepared in situ from p-toluenesulfonyl hydrazide in diglyme. The present method was applicable to the synthesis of saturated 12- and 18-membered oligosilacycloalkanes.
Journal ArticleDOI
TL;DR: In this paper, the stereoselective synthesis of dl -siccanin (1) and dl-siccanene E (2) has been described, and a novel tetrahydrofuran formation by a neighboring participation, which was observed in hydroxy ketone 24 and diol 32, are also discussed.
Abstract: The stereoselective synthesis of dl -siccanin (1) and dl -siccano-chromene E (2) has been described. Acid isomerization of nonconjugated octalone 11a, derived from known octalone 5, stereoselectively provided cis-fused octalone 12, from which cis -drimane aldehyde 31 was obtained. After condensation of 31 with lithio-orcinol dimethyl ether, the product 32 was treated with pyridinium chloride to give tetrahydrofuran 33 whose complete stereostructure was unambiguously established by an X-ray crystal analysis. While cyclization of monophenol 34, obtained by partial demethylation of 33, with sulfuric acid afforded siccanochromene E methyl ether (35), reaction of 34 with Lewis acid gave siccanin methyl ether (36) along with 35. In the latter cyclization, the formation of 36 was demonstrated to occur from initially formed 35. Finally, demethylation of 35 and 36 provided 2 and 1, respectively. A novel tetrahydrofuran formation by a neighboring participation, which was observed in hydroxy ketone 24 and diol 32, are also discussed.

Cited by
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TL;DR: In this paper, the authors used 13C and 1H NMR spectra of graphite oxide derivatives to confirm the assignment of the 70 ppm line to C−OH groups and allow them to propose a new structural model for graphite oxides.
Abstract: Graphite oxide (GO) and its derivatives have been studied using 13C and 1H NMR. NMR spectra of GO derivatives confirm the assignment of the 70 ppm line to C−OH groups and allow us to propose a new structural model for GO. Thus we assign the 60 ppm line to epoxide groups (1,2-ethers) and not to 1,3-ethers, as suggested earlier, and the 130 ppm line to aromatic entities and conjugated double bonds. GO contains two kinds of regions: aromatic regions with unoxidized benzene rings and regions with aliphatic six-membered rings. The relative size of the two regions depends on the degree of oxidation. The carbon grid is nearly flat; only the carbons attached to OH groups have a slightly distorted tetrahedral configuration, resulting in some wrinkling of the layers. The formation of phenol (or aromatic diol) groups during deoxygenation indicates that the epoxide and the C−OH groups are very close to one another. The distribution of functional groups in every oxidized aromatic ring need not be identical, and both ...

3,076 citations

Journal ArticleDOI
TL;DR: Hydrogenation of Alkenes and Arenes by Nanoparticles 2624 3.1.2.
Abstract: 2.5. Stabilization of IL Emulsions by Nanoparticles 2623 3. Hydrogenations in ILs 2623 3.1. Hydrogenation on IL-Stabilized Nanoparticles 2623 3.1.1. Hydrogenation of 1,3-Butadiene 2623 3.1.2. Hydrogenation of Alkenes and Arenes 2624 3.1.3. Hydrogenation of Ketones 2624 3.2. Homogeneous Catalytic Hydrogenation in ILs 2624 3.3. Hydrogenation of Functionalized ILs 2625 3.3.1. Selective Hydrogenation of Polymers 2625 3.4. Asymmetric Hydrogenations 2626 3.4.1. Enantioselective Hydrogenation 2626 3.5. Role of the ILs Purity in Hydrogenation Reactions 2628

1,996 citations

Journal ArticleDOI
TL;DR: The increasing demand to produce enantiomerically pure pharmaceuticals, agrochemicals, flavors, and other fine chemicals has advanced the field of asymmetric catalytic technologies, and asymmetric hydrogenation utilizing molecular hydrogen to reduce prochiral olefins, ketones, and imines has become one of the most efficient methods for constructing chiral compounds.
Abstract: The increasing demand to produce enantiomerically pure pharmaceuticals, agrochemicals, flavors, and other fine chemicals has advanced the field of asymmetric catalytic technologies.1,2 Among all asymmetric catalytic methods, asymmetric hydrogenation utilizing molecular hydrogen to reduce prochiral olefins, ketones, and imines, have become one of the most efficient methods for constructing chiral compounds.3 The development of homogeneous asymmetric hydrogenation was initiated by Knowles4a and Horner4b in the late 1960s, after the discovery of Wilkinson’s homogeneous hydrogenation catalyst [RhCl(PPh3)3]. By replacing triphenylphosphine of the Wilkinson’s catalystwithresolvedchiralmonophosphines,6Knowles and Horner reported the earliest examples of enantioselective hydrogenation, albeit with poor enantioselectivity. Further exploration by Knowles with an improved monophosphine CAMP provided 88% ee in hydrogenation of dehydroamino acids.7 Later, two breakthroughs were made in asymmetric hydrogenation by Kagan and Knowles, respectively. Kagan reported the first bisphosphine ligand, DIOP, for Rhcatalyzed asymmetric hydrogenation.8 The successful application of DIOP resulted in several significant directions for ligand design in asymmetric hydrogenation. Chelating bisphosphorus ligands could lead to superior enantioselectivity compared to monodentate phosphines. Additionally, P-chiral phosphorus ligands were not necessary for achieving high enantioselectivity, and ligands with backbone chirality could also provide excellent ee’s in asymmetric hydrogenation. Furthermore, C2 symmetry was an important structural feature for developing new efficient chiral ligands. Kagan’s seminal work immediately led to the rapid development of chiral bisphosphorus ligands. Knowles made his significant discovery of a C2-symmetric chelating bisphosphine ligand, DIPAMP.9 Due to its high catalytic efficiency in Rh-catalyzed asymmetric hydrogenation of dehydroamino acids, DIPAMP was quickly employed in the industrial production of L-DOPA.10 The success of practical synthesis of L-DOPA via asymmetric hydrogenation constituted a milestone work and for this work Knowles was awarded the Nobel Prize in 2001.3k This work has enlightened chemists to realize * Corresponding author. 3029 Chem. Rev. 2003, 103, 3029−3069

1,995 citations