Asymmetric conjugate reduction of alpha,beta-unsaturated ketones and esters with chiral rhodium(2,6-bisoxazolinylphenyl) catalysts

New asymmetric conjugate reduction of beta,beta-disubstituted alpha,beta-unsaturated ketones and esters was accomplished with alkoxylhydrosilanes in the presence of chiral rhodium(2,6-bisoxazolinylphenyl) complexes in high yields and high enantioselectivity. (E)-4-Phenyl-3-penten-2-one and (E)-4-phenyl-4-isopropyl-3-penten-2-one were readily reduced at 60 degrees C in 95 % ee and 98 % ee, respectively, by 1 mol % of catalyst loading. (EtO)2MeSiH proved to be the best hydrogen donor of choice. tert-Butyl (E)-beta-methylcinnamate and beta-isopropylcinnamate could also be reduced to the corresponding dihydrocinnamate derivatives up to 98 % ee.     

Preparation of novel aluminohydride complexes of ruthenium(II)

Treatment of (η⁵-C₅Me₅)RuCl₂(PR₃) (1) with LiAlH₄ in diethyl ether gives the ruthenium(II) tetrahydroaluminate complexes, (η⁵-C₅Me₅)Ru(AlH₄)(PR₃) (2) (R₃ = Me₃, Et₃, ⁱPr₃, Ph₂Me, Ph₃), which can be quantitatively converted to the trihydriodurthenium(IV) complexes (η⁵-C₅Me₅)RuH₃(PR₃) (4), via protonolysis either by reaction with ethanol or by filtration through alumina. Low-temperature ¹H NMR studies suggest the fluxionality of complexes 2 in solution at ambient temperature.     

The structure changes and the spin phase transition mechanism of a spin crossover complex, [Fe(2-pic)3]Cl2·EtOH

The crystal structure of the spin crossover complex [Fe(2-pic)₃]Cl₂·EtOH in its high spin state (298, 150 K) and low spin state (90 K) has been determined. The crystals are monoclinic, P2₁/c with Z=4 in the two spin states. Pronounced changes in the FeN bond distance (2.195 A for high spin, 2.013 A for low spin on average) and orientational disorder of the ethanol molecule were observed. The complexes and ethanols are both hydrogen bounded to Cl^? ions.     

Hydroalumination of olefins catalyzed by immobilized titanium compounds

SiO₂-supported titanium chloride ($\text{1}$) and polystyrene-supported titanocene dichloride ($\text{2}$) and ($\text{3}$) were synthesized. These heterogenized titanium compounds are excellent catalysts for hydroalumination of olefins.     

The size and mass distribution of firebrands collected from ignited building components exposed to wind

Wildfires that spread into communities, commonly referred to as Wildland-Urban Interface fires (WUI), are a significant international problem. Post-fire damage studies have suggested for some time that firebrands are a significant cause of structure ignition in WUI fires, yet little research has been conducted to investigate firebrand production from burning vegetation and structures. To this end, firebrand production from real-scale building components under well-controlled laboratory conditions was investigated. Specifically, wall and re-entrant corner assemblies were ignited and during the combustion process, firebrands were collected to determine the size/mass distribution generated from such real-scale building components under varying wind speed. Finally, the size and mass distributions of firebrands collected in this study were compared with the data from an actual full-scale structure burn to determine if simple component tests such as these can provide insights into firebrand generation data from full-scale structures. The results are presented and discussed.     

Reverse enantioselectivity in the lipase-catalyzed desymmetrization of prochiral 2-carbamoylmethyl-1,3-propanediol derivatives

Enantioselective acetylation of 2-carbamoylmethyl-1,3-propanediol derivatives was catalyzed effectively by lipase PS to give monoacetates with high enantioselectivity: The enantioselectivity depended on the 2-carbamoylmethyl groups. The reaction of N-monoalkylcarbamoylmethyl-1,3-propanediol afforded the monoacetate with the (S)-configuration, whereas N,N-dialkylcarbamoylmethyl-1,3-propanediol gave the monoacetate with the (R)-configuration.     

Magnetic resonance elastography using an air ball-actuator

The purpose of this study was to develop a new technique for a powerful compact MR elastography (MRE) actuator based on a pneumatic ball-vibrator. This is a compact actuator that generates powerful centrifugal force vibrations via high speed revolutions of an internal ball using compressed air. This equipment is easy to handle due to its simple principles and structure. Vibration frequency and centrifugal force are freely adjustable via air pressure changes (air flow volume), and replacement of the internal ball. In order to achieve MRI compatibility, all parts were constructed from non-ferromagnetic materials. Vibration amplitudes (displacements) were measured optically by a laser displacement sensor. From a bench test of displacement, even though the vibration frequency increased, the amount of displacement did not decrease. An essential step in MRE is the generation of mechanical waves within tissue via an actuator, and MRE sequences are synchronized to several phase offsets of vibration. In this system, the phase offset was detected by a four-channel optical-fiber sensor, and it was used as an MRI trigger signal. In an agarose gel phantom experiment, this actuator was used to make an MR elastogram. This study shows that the use of a ball actuator for MRE is feasible.     

Ruthenium-catalyzed transfer oxygenative cyclization of α,ω-diynes: unprecedented [2 + 2 + 1] route to bicyclic furans via ruthenacyclopentatriene

A novel oxygen-atom-transfer process enables the catalytic [2 + 2 + 1] synthesis of bicyclic furans from α,ω-diynes with DMSO. [CpRu(AN)(3)]PF(6) catalyzed the transfer oxygenative cyclization of diynes with aryl terminal groups, while those of diynes with alkyl terminal groups were effectively promoted by the corresponding Cp* complex. A mechanism for bicyclic furan formation via a ruthenacyclopentatriene was proposed on the basis of both experimental and theoretical studies.     

Theory of optical analysis of inhomogeneous turbid textures

A trial theory of optical diagnosis of inhomogeneous and turbid materials is firstly proposed, considering mutual photon exchanges due to scattering among conglomerate textures. Including scattering and redistribution of photons between neighboring segments, a collective model of photon flow behaviors is analytically constructed. Employing simple inhomogeneous parameters, a set of equations is formulated to express quasi three-dimensional photon redistribution between segments. The important feature of the theory is a simple framework regarding the complex photon flow to be solved by linear algebra. For qualitative and quantitative analyses of respective components, the simultaneous equations can be solved with their characteristic optical coefficients. Each of the ingredients can be analytically identified and evaluated separately. Some of the calculations are exemplified, to show differences from conventional homogeneous theory. Advantageous applications in medical diagnosis are suggested.