Tetsuo Kusumoto

Reductive coupling of carbonyl compounds to pinacols by using low-valent cerium

Abstract Aldehydes and ketones, on treatment with a low-valent cerium reagent, undergo reductive dimerization to produce the corresponding pinacols in high yield.

A new aldol reaction via cerium enolates

Abstract Cerium enolates formed from cerium (III) chloride and lithium enolates undergo aldol reaction with ketones or sterically crowded aldehydes to afford the corresponding β-hydroxyketones in high yields.

An Unusual Endothermic Transition to an Optically Isotropic Phase Organized by Chiral Molecular Recognition

A novel chiral liquid crystal was found to exhibit an endothermic transition upon cooling from a chiral smectic C phase to an optically isotropic phase. C-13 NMR and X-ray diffraction indicate that the isotropic phase has a layered structure in which fast isotropic reorientation of molecules or molecular assemblies occurs. We suggest that molecular aggregation via chiral recognition breaks anisotropic molecular ordering, which leads to a novel phase structure.

Palladium catalyzed double silylation of bis(trimethylsilyl)butadiyne by means of disilanes

Abstract Reaction of bis(trimethylsilyl)butadiyne with Si 2 Cl x Me 6-x in the presence of a palladium catalyst gives, after methylation, 1,1,4,4-tetrakis(trimethylsilyl)butatriene and/or 1,1,2,4-tetrakis- (trimethylsilyl)-1-buten-3-yne selectively.

A Bent and Asymmetrically Hindered Chiral Alkyl Chain in Smectic-A Phase of an Antiferroelectric Liquid Crystal as Observed by 2H-NMR.

The structure and dynamics of the alkyl chains are investigated by 2 H-NMR for specifically deuterated samples of an antiferroelectric chiral smectic liquid crystal MHPOBC. The 2 H-NMR spectrum for the chiral alkyl chain exhibits very small quadrupolar splittings, and the methylenes close to the chiral center give double splittings ascribable to two different quadrupolar splittings for each methylene unit. The unusual nature of the chiral chain is revealed; the chain is bent from the molecular long axis, and is asymmetrically hindered.

Structures in optically isotropic and bluish colored cubic phases formed by enantiomeric association in an (R,S) dichiral compound and a stereoisomeric (R,R) and (S,S) mixture

The structures of an optically isotropic cubic phase and a bluish colored phase exhibited in an (R,S) dichiral compound with fluorines have been investigated. Not only the bluish colored phase but also the cubic phase exhibit circular dichroism, being confirmed to be chiral phases. Based on the analysis of several X-ray diffraction peaks observed in the small angle range, we find that the optically isotropic chiral cubic (IsoX) phase belongs to the symmetry group I432. It is also found that the cubic phase emerging in the equimolar mixture of (R,R) and (S,S) stereoisomers also has I432 symmetry, suggesting the formation of the cubic phase due to chiral recognition between chiral end chains. The molecular recognition upon forming the IsoX phase is also discussed by mixing (R,R) and (S,S) stereoisomers in the crystalline phase. The other important finding is the exotic phase with a blue colored and foggy texture below the isotropic liquid. X-Ray diffraction results in this phase clearly show a diffraction ring corresponding to a layer structure with a quite long correlation length. We assigned this phase to a smectic blue phase (BPsm).

Anomalous behaviours of the heat capacity in a liquid crystal showing a re-entrant isotropic phase

High resolution a.c. calorimetric measurements have been carried out on a liquid crystal 2-{4-[(R)-2-fluorohexyloxy]phenyl}-5-{4-[(S)-2-fluoro-2-methyldecanoyloxy]phenyl}pyrimidine (RSFPPY), determined the present measurement revealed precise temperature dependence of the heat capacity over a wide temperature range including the phase transition temperatures. The isotropic-chiral smectic C transition was anomalous in that it showed quite different behaviours depending on whether the measurement was made on heating or cooling; that is attributed to the relaxational character of the transition. A new non-transitional feature in the isotropic phase was found, corresponding to a very broad heat capacity peak over a 30 K temperature range. This indicates an existence of a new phase, possibly some kind of blue phase, at the lower temperature side of the isotropic phase. (RSFPPY), determined the present measurement revealed precise temperature dependence of

New chiral dopants for FLC materials: optically active cyclic ethers

Abstract A series of new optically active cyclic ethers such as tetrahydrofurans, chromans and dihydrobenzofurans were synthesized, and their physical properties as a chiral dopant for FLC were investigated. Correlation between the the chemical structures and the physical properties, especially spontaneous polarization (Ps), are discussed and compared with that of the corresponding lactones.

Synthesis of 5-amino-2-cyano-4-silylpyrroles from silylacetylenes and trimethylsilyl cyanide

Abstract The reaction of silylacetylenes with trimethylsilyl cyanide in the presence of palladium catalysts gives 3-substituted 5-[N,N-bis(trimethylsilyl)amino]-2-cyano-4-silylpyrroles with high regioselectivity.

Synthesis of optically active t-butyl (3R,5S)-3,5-isopropylidenedioxy-6-heptynoate through baker's yeast reduction of methyl 3-oxo-4-pentynoate

Bakers yeast reduction of methyl 3-oxo-4-pentynoate gave the corresponding (S)-3-hydroxy ester (80% e.e.), whereas its 5-trimethylsilyl derivative gave the (R)-enantiomer (82% e.e.). The (S)-alcohol was led to optically active t-butyl (3R,5S)-3,5-isopropylidenedioxy-6-heptynoate, a versatile synthetic intermediate of artificial HMG-CoA reductase inhibitors.