Kenji Itoh

Bis(1-3:5-6-η-cyclooctadienyl)ruthenium: Preparation, NMR spectroscopy, and isomerization to (η6-1,3,5-cyclooctatriene)(1-2:5-6-η-1,5-cyclooctadiene)ruthenium via the activation of a CH bond

Abstract The complex Ru(1-3:5-6-η-C 8 H 11 ) 2 (II) was prepared by the reduction of ruthenium trichloride hydrate with zinc in the presence of 1,5-cyclooctadiene at room temperature. Complex II, isomerized to Ru(η 6 -C 8 H 10 )(1-2:5-6-η-C 8 H 12 ) (I) at 70°C by the migration of a hydrogen atom from one l-3:5-6-η-C 8 H 11 ligand to the other. The 1 H and 13 C NMR spectral evidence including selective irradiation studies suggests unsymmetrical coordination of the olefinic moiety of the 1-3:5-6-η-C 8 H 11 ligand in the complex II.

Preparation and synthetic application of 2-bromoallyltrimethylsilane as a 1-hydroxymethylvinyl anion equivalent

Abstract The 1-trimethylsilylmethylvinyl group, as a 1-hydroxymethylvinyl equivalent, was readily introduced to epoxides with the corresponding Grignard reagent derived from 2-bromoallyltrimethylsilane. Obtained 2-(2-hydroxy-ethyl)-allylsilanes were converted to α-methylene-γ-lactones via diols.

Silicas chemically bonded with multidentate phenyl groups as stationary phases in reversed-phase liquid chromatography used for non-planarity recognition of polycyclic aromatic hydrocarbons

Abstract Multidentate phenyl-bonded phases have been evaluated as stationary phases which can recognize molecular non-polarity of polycyclic aromatic hydrocarbons. The results clearly indicate that these multidentate give a higher non-polarity recognition capability than that with typical octadecylsilicas such as polymeric and monomeric phases. The reason for this mechanism can be interpreted by the molecular—molecular interaction between a solute and a stationary phase and this kind of approach will open the possibility of designing new stationary phases which offer more selective of specific separations.

Liquid chromatographic separation of all-carbon molecules C60 and C70 with multi-legged phenyl group bonded silica phases

Abstract The separation of C60 and C70 all-carbon compounds has been examined using new multi-legged phenyl group bonded silicas as the stationary phase in liquid chromatography. Two-legged biphenyl bonded silica gave the best separation because this phase offers the most suitable cavity-like structure to retain the C70 molecule, and this provides good separation between C60 and C70.

Stereoselectivity in hydrosilylative reduction of substituted cyclohexanone derivatives with chiral rhodium-bis(oxazolinyl)pyridine catalyst

Abstract Stereoselectivity in the reduction of substituted cyclohexanones, 4-tert-butylcycohexanone, 2-methylcycohexanone, 2-phenylcyclohexanone, and 2-methoxycarbonyl-methylcyclohexanone, was examined with chiral rhodium-bis(oxazolinyl)pyridine catalyst and diphenylsilane. 4-tert-Butylcyclohexanone gave the corresponding trans( equatorial )-alcohol predominantly; the ratio of the trans/cis alcohols, 67:33. Other 2-substituted cyclohexanones showed exclusive enantioselectivities for each diastereomer in terms of the kinetic resolution; e.g. from 2-phenylcyclohexanone, 99 % ee of (1S, 2R)-trans-2-phenylcyclohexanol and 96 % ee of (1S, 2S)-cis-2-phenylcyclohexanol in 92 % yield (the trans/cis ratio = 51:49).

New regio- and stereoselective preparation of trichlorinated γ-butyrolactones by copper catalyzed cyclization of allyl trichloroacetates

Abstract A novel synthetic method for γ-butyrolactones is presented. The process involves high regioselectivity to afford γ-lactones. In cases of trichloroacetates of secondary allylic alcohols, high cis -selective cyclization is accomplished.

Dimethoxyphenylpropyl bonded silica phase for higher fullerenes separation by high-performance liquid chromatography

Fullerenes were separated using three chemically bonded phases, dimethoxyphenylpropyl (DMP), monomeric octadecyl and polymeric octadecyl modified silicas (ODS), with n-hexane as the mobile phase. DMP and the monomeric ODS are the best choices for the separation of C60 and C70 compounds, while DMP is the only phase that has high temperature stability while maintaining the resolution. For the separation of higher fullerenes, DMP offers faster analysis at higher temperatures while maintaining its high resolution, whereas ODS phases cannot provide similar run times while offering the same resolution. In conclusion, DMP is the most suitable and promising stationary phase for fullerenes analysis because of the short run time and its superior separation efficiency.

New stereocontrolled approach to some insect pheromones via silicon-directed beckmann fragmentation

Abstract The major components of sex pheromones of potato tuberworm moth and Douglas fir tussock moth have been synthesized via the regio- and stereo-controlled Beckmann fragmentation assisted by trimethylsilyl group.

Silicon-directed beckmann fragmentation

Abstract The selective fragmentation reactions of β-trimethylsilylketoximes have been proved to proceed effectively with acid catalysts giving the corresponding nitriles. Cyclic silylketoximes gave unsaturated nitriles. The fragmentation in the Beckmann rearrangement is completely controlled and directed by a trimethylsilyl group to lead the regio- and stereo-specific formation of the double bond. The catalytic fragmentation proceeds with the combination of trimethylsilyl ketoxime acetates and trimethylsilyl trifluoromethanesulfonate giving nitriles in high yields. Excellent stereospecificity of the fragmentation based on the stereochemical outcome was discussed. Simple stereo-controlled synthetic approach to some insect pheromones is also described.

Separation and identification of fullerenes by liquid chromatography

SummaryThe separation of fullerenes with a monomeric octadecylsilica bonded phase using n-hexane or toluene/methanol mobile phase systems is described. Analytical and preparative separations, incorporating on-line UV/VIS spectral measurements, confirmed the existence of large fullerenes such as C76, C78 and C84. However, isomers of C78 and C84 were not conclusively found.