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 ...

Structure of Graphite Oxide Revisited

Synthetic Principles for Bandgap Control in Linear pi-Conjugated Systems.

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

Catalysis in ionic liquids

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

New Chiral Phosphorus Ligands for Enantioselective Hydrogenation

Asymmetric 1,3-Dipolar Cycloaddition Reactions

Phenyl[tris(trimethylsilyl)]ethylene bis(lithium dimethoxyethane) was prepared as black crystals. The molecular structure determined by the X-ray diffraction method shows several interesting features. One of the lithium atoms is located near the central two carbon atoms, while the other is above the benzene ring and the central C–C bond is twisted by 92°.

Molecular structure of phenyl[tris(trimethylsilyl)]ethylene dilithium complex. An orthogonal dianion

Chemistry of organosilicon compounds: CCXXXVI. Structure of conformationally stable 1-(p-bromophenyl)-4-t-butyl-1-methyl-1-silacyclohexane and stereochemistry of halodesilylation

Oxidation of sterically-crowded selones using chloramine-T: generation and skeletal rearrangement of selone Se -imides

1,2,3,4-テトラ-t-ブチル-1,2,3,4-テトラフェニルシクロテトラゲルマン(3)をベンゼン中,塩化アルミニウム触媒存在下,塩化水素の作用で四官能性の1,2,3,4-テトラ-t-ブチル-1,2,3,4-テトラクロロシクロテトラゲルマン(4)に変換しだ.化合物4は4種の可能な立体異性体中,熱力学的に安定なtrans-の配置であることをX線結晶構造解析によって明らかにした.シクロテトラゲルtマranンs-(t4r)ansをTHF中,金属ナトリウムで縮合させると4,8-ジクロロオクタ-t-ブチルテトラシクロ[3.3.0.02,7.03,6]オクタゲルマン(6)と3,4,7,8-テトラクロロオクタ-t-ブチルトリシクロ[4.2.0.02.5]オクタゲルマン(7)が生成した.ポリゲルマン(7)は2個の四員環がアンチ形に連結したはしご形ポリゲルマンであることをX線結晶構造解析によって明らかにした.

Chemistry of Germanium-Characteristics and Similarity as a Group 14 Element. Synthesis and Characterization of Cyclotetragemane and Ladder Polygermane with Functional Groups.

The title compound and the related poly(disilanyl)ethylenes were prepared by the reaction of 1,2-bis(bromodimethylsilyl)-1,2-bis(chlorodimethylsilyl)ethylene with trimethylsilyllithium in HMPA/THF. The physical properties of the title compound as well as its molecular structure by X-ray diffraction are described.

Chizuko Kabuto

Papers

Molecular structure of phenyl[tris(trimethylsilyl)]ethylene dilithium complex. An orthogonal dianion

Chemistry of organosilicon compounds: CCXXXVI. Structure of conformationally stable 1-(p-bromophenyl)-4-t-butyl-1-methyl-1-silacyclohexane and stereochemistry of halodesilylation

Oxidation of sterically-crowded selones using chloramine-T: generation and skeletal rearrangement of selone Se -imides

Chemistry of Germanium-Characteristics and Similarity as a Group 14 Element. Synthesis and Characterization of Cyclotetragemane and Ladder Polygermane with Functional Groups.

Synthesis, Properties, and Molecular Structure of Tetrakis(pentamethyldisilanyl)ethylene