Takashi Miura

New Chiral Diphosphine Ligands Designed to have a Narrow Dihedral Angle in the Biaryl Backbone

A series of novel optically active diphosphine ligands, (4,4′-bi-1,3-benzodioxole)-5,5′-diylbis(diarylphosphine)s (6), which are called SEGPHOS, has been designed and synthesized with dihedral angles in the Ru complexes being less than that in the corresponding BINAP-Ru complex. The stereorecognition abilities of SEGPHOS-Ru complex catalysts in the asymmetric catalytic hydrogenation of a wide variety of carbonyl compounds are superior to those observed with BINAP-Ru complex catalysts.

The dual role of ruthenium and alkali base catalysts in enabling a conceptually new shortcut to N-unsubstituted pyrroles through unmasked α-amino aldehydes.

A virtually salt-free and straightforward bimolecular assembly giving N-unsubstituted pyrroles through fully unmasked α-amino aldehydes, which was enabled by the dual effects of a catalytic ruthenium complex and an alkali metal base, is reported. Either solvent-free or acceptorless dehydrogenation facilitates high atom, step, and pot economy, which are otherwise difficult to achieve in multistep operations involving protection/deprotection.

Diastereoselective synthesis of a key intermediate for the preparation of tricyclic β-lactam antibiotics

Abstract Asymmetric synthesis of ( S )- 5 has been accomplished with an excellent enantiomeric excess by hydrogenation of racemic 5 using ruthenium-BINAP-diamine-KOH system, followed by oxidation. Magnesium enolate of (2 S )-2-methoxycyclohexanone [( S )- 5 ] reacts with the 4-acetoxyazetidinone 4 to give the key intermediate 3 with high yield and diastereoselectivity for the synthesis of sanfetrinem 1 .

CuI/H2/NaOH-Catalyzed Cross-Coupling of Two Different Alcohols for Carbon–Carbon Bond Formation: “Borrowing Hydrogen”?

To minimize salt waste byproducts and to save energy and resources during the manufacture of longer-chain (higher) alcohols, transition-metal-catalyzed direct coupling between alcohols has recently been reinvestigated. Homocoupling of the carbon atoms of primary alcohols was first demonstrated as a Guerbet reaction using excess alkaline metal alkoxides at a high pressure/temperature ( 220 8C). Recent Guerbet reactions using transition-metal catalysts were proposed to involve a “borrowing hydrogen” process consisting of 1) transition metal-catalyzed oxidation (transfer dehydrogenation) of both alcohols to form the corresponding carbonyl compounds; 2) base-catalyzed aldol condensation of them to form a,b-unsaturated carbonyl compounds, and 3) transition metal-catalyzed concomitant reduction (transfer hydrogenation) of the C=C and C=O bonds using the borrowed hydrogen atoms from both alcohols. Thus far, precious metals Ir and Ru, respectively, have been the most widely used for this purpose and such catalyst precursors have shown reasonable reactivity by subtle modification of the original conditions. However, reaction conditions used to date for Guerbet variants are so diverse that the critical factors for promoting the reactions have been veiled: in many cases, the reaction utilizes significant amounts of base (1–3 equiv with respect to one of two substrates), 4a,b, 5a,c–g,6b–d,h,7] and/or sacrificial hydrogen (H2) acceptors, [3b, 5a,f] with a few exceptions. In some cases, the molar amount of one of the two different alcohols used exceeded 7a] that of the other (e.g., 1/2=1:2 or 2:1 equiv). A H2 atmosphere was detrimental to the productivity of higher alcohols using a hetereogeneous catalyst. We report herein a notable advancement in this field, based on our demonstration that simple Cu/H2/NaOH catalysts are able to catalyze the cross-coupling between a range of two different alcohols; the coupling showed a wider substrate scope with the best practicality for the selective synthesis of higher alcohols (Scheme 1). Most impor-

Asymmetric synthesis of (R)-2-chloro-1-(m-chlorophenyl)ethanol using acetone powder of Geotrichum candidum

The asymmetric synthesis of (R)-2-chloro-1-(m-chlorophenyl)ethanol, a precursor for a key intermediate of an important class of drugs, was achieved by reduction of the corresponding ketone using an acetone powder of Geotrichum candidum with 98% ee and 94% yield based on the starting amount of ketone.

A convenient preparative method for β-lactams from β-amino acids using sulfenamide/triphenylphosphine

Abstract β-, γ-, and δ-Amino acids were easily cyclized in high yields to corresponding β-, γ-, and δ-lactams by treatment with N -alkyl-2-benzothiazolylsulfenamide and triphenylphosphine.

A simple and highly diastereoselective synthesis of a 1β-methylcarbapenem key intermediate by deallyloxycarbonylation using palladium complexes

Abstract A Simple, highly diastereoselective synthesis of the key 1β-methylcarbapenem intermediate 1 has been accomplished via a palladium catalyzed deallyloxycarbonylation of diallyl malonate derivative 4a which was readily prepared from (3S,4R)-4-acetoxy-3-[(R)-1-(t-butyldimethylsilyloxy)ethyl]-2-azetidinone 2 in two steps.

Dielectric and Magnetic Properties of a Titanium Oxide and Carbonyl Iron Composite Material and Application as a Microwave Absorber

A microwave absorber for use in an electronic toll collection (ETC) device, having a central frequency of 5.8 GHz, is fabricated using a composite of dielectric (titanium oxide, TiO2) and magnetic (carbonyl iron, Fe(CO)5) materials. The reflection loss in free space, using a circularly polarized wave, was -20 dB or more around a central frequency of 5.8 GHz at incident angles of up to 60°, which satisfy the necessary conditions for ETC use.

Multifaceted catalytic hydrogenation of amides via diverse activation of a sterically confined bipyridine–ruthenium framework

Amides are ubiquitous and abundant in nature and our society, but are very stable and reluctant to salt-free, catalytic chemical transformations. Through the activation of a “sterically confined bipyridine–ruthenium (Ru) framework (molecularly well-designed site to confine adsorbed H2 in)” of a precatalyst, catalytic hydrogenation of formamides through polyamide is achieved under a wide range of reaction conditions. Both C=O bond and C–N bond cleavage of a lactam became also possible using a single precatalyst. That is, catalyst diversity is induced by activation and stepwise multiple hydrogenation of a single precatalyst when the conditions are varied. The versatile catalysts have different structures and different resting states for multifaceted amide hydrogenation, but the common structure produced upon reaction with H2, which catalyzes hydrogenation, seems to be “H–Ru–N–H.”

Extension of Physical Limit of Conventional Metal-Oxide-Semiconductor Transistor by Double Barriers Formed at the Channel Edges

A method to extend the physical limit of the conventional (conv.) metal-oxide-semiconductor transistor (MOST) is presented. Suppression of the direct tunneling (DT) from the source to the drain using double barriers at the channel edges is discussed. The parameters of the operation characteristics for the quantum mechanical channel length are also discussed from the viewpoint of the barrier height of the dielectric films which are formed at both edges of the channel.