Facile Dehydrogenation of alpha-Amino Acids Chelated to a Ruthenium(II) Ion: (alpha-Imino acidato)ruthenium(II) Complexes

(alpha-Imino acidato)ruthenium(II) complexes, [Ru(II){N(R(1))=C(R(2))CO(2)}L(2)](+) (R(1) = R(2) = Me or R(1) = R(2) = -(CH(2))(3)-; L = 2,2'-bipyridine (=bpy) or 1,10-phenanthroline (=phen)), were obtained by anodic oxidation at a constant potential of the corresponding (alpha-amino acidato)ruthenium(II) complexes, N-methylalaninato or prolinato complexes, in good to excellent yields. (alpha-Imino acidato)ruthenium(II) complexes are stable in neutral or acidic aqueous solution. The half-wave potentials of alpha-imino acidato complexes are 0.73-0.78 V (vs SCE), which are more positive than those of the corresponding alpha-amino acidato complexes, 0.55-0.59 V. The crystal structure of [Ru(pro-H(2))(bpy)(2)]ClO(4).3H(2)O (pro-H(2) = 1,2-didehydroprolinato) has been determined by single-crystal X-ray analysis. Crystallographic data: space group C2/c, a = 21.73(1) ?, b = 19.33(1) ?, c = 14.58(1) ?, beta = 114.91(5) degrees, Z = 8, R = 0.0352. The length of the C=N double bond of the alpha-imino acidate moiety is 1.294(5) ?, and Ru-N(imino nitrogen) = 2.042(3) ?. The chelate ring of the alpha-imino acidato ligand is planar.     

Synthetic studies of carbapenem and penem antibiotics. III. A synthesis of a key intermediate for 1 beta-methylcarbapenem.

We synthesized useful intermediates 5 and 6 for 1 beta- and 1 alpha-methylcarbapenems from 4-carboxy-3-[(R)-1-hydroxyethyl]-2-azetidinone 4 as a starting material by using stereoselective hydrogenation and hydroboration, respectively. A practical synthetic route from 4 to the (3S,4S)-4-[(R)-1-carboxyethyl]-3-[(R)-1-hydroxyethyl]-2-azetidinone derivative 1, a useful intermediate for the synthesis of 1 beta-methylcarbapenem antibiotics, was established.     

Increase in the mobility of photogenerated positive charge carriers in polythiophene

We report the increase in the mobility of charge carriers in regioregular poly 3-hexyl thiophene (RR-P3HT) films by mixing them with tetracyanoethylene (TCNE), which is examined by in situ time-resolved microwave conductivity (TRMC) and transient optical spectroscopy (TOS). TCNE acts not only as an electron acceptor which increases the number of charge carriers on photoexposure but also as a functional additive which enhances the mobility of the charge carriers. This conclusion was deduced from the results of fluorescence quenching, transient optical absorption and photobleaching, and comparison of the TRMC signal with the TOS signal. The combination of the TRMC and TOS techniques represents a comprehensive and fully experimental approach to the determination of the intrinsic carrier mobility in conjugated polymers.     

Effective biaryl compound synthesis using cross-coupling reaction with nickel complexes coordinated by diaminophosphine ligands

The cross-coupling reaction of aryl halides and aryl Grignard reagents was effectively catalyzed by the diaminophosphine complex catalysts and the reaction was much faster than that catalyzed by aminophosphine complexes and the nickel complexes were more active than palladium complexes. Various biaryl compounds were easily prepared by the reaction with nickel diaminophosphine catalysts.     

A novel chiral phosphinediamine ligand and asymmetric hydrogenation of acrylic acid derivatives

A novel chiral phosphinediamine ligand (PN₂) was prepared from (S)-1-phenylethylamine and dichloroisopropylphosphine. The rhodium-PN₂ catalyst utilizing selective ligation of the amino unit and electrostatic interaction between the ligand and a substrate gave high enantioselectivities up to 92% ee in asymmetric hydrogenations of acrylic acid derivatives.     

Radical polymerization of isopropyl tert-butyl fumarate and maleate,and characterization of the resulting polymers

Radical polymerization of isopropyl tert-butyl fumarate (iPtBF) and monomer-isomerization radical polymerization of isopropyl tert-butyl maleate (iPtBM) were investigated with 2,2′-azobisisobutyronitrile as initiator in the presence and absence of morpholine (Mor) as isomerization catalyst. It was found that iPtBF gave high molecular weight polymers in high yield as previously observed for diisopropyl fumarate (DiPF) and di-tert-butyl fumarate (DtBF). It was confirmed that iPtBF produced by in situ monomer isomerization of iPtBM homopolymerized to give a polymer. Radical copolymerization of iPtBM with styrene in the presence and absence of Mor was also performed and monomer reactivity ratios obtained were compared. From the kinetic study of the isomerization of iPtBM, it was revealed that the isomerization rate showed first-order dependence on the concentration of iPtBM and Mor, and that the apparent activation energy was 29.4 kJ/mol. On pyrolysis of the poly(iPtBF) at 180°C, isobutene and isopropanol were eliminated rapidly to yield polymer containing carboxyl groups and anhydrides. The pyrolytic behavior was different from that of a copolymer of DiPF with DtBF.     

Efficient anodic pyridination of poly(3-hexylthiophene) toward post-functionalization of conjugated polymers

Nucleophilic substitution reaction of poly(3-hexylthiophene) (P3HT) with pyridine derivatives as nucleophile was demonstrated in anodic oxidation process. The key reaction involves efficient nucleophilic attack of the pyridine derivatives toward thiophene rings in partly oxidized polymer, i.e., doped state, in the similar manner in which anodic pyridination of electrochemically generated pi-radical cation of a series of oligothiophene takes place in quantitative yield (Y. Li, K. Kamata, T. Kawai, J. Abe and T. Iyoda, J. Chem. Soc., Perkin Trans. 1, 2002, 1135-1140). When 1-methyl-4-(4'-pyridyl)pyridinium hexafluorophosphate (MPP+PF6-) was used as a functional nucleophile, the anodic pyridination reaction gave viologen-tailored poly(3-hexylthiophene) (P3HT), which was confirmed by electrochemical and spectroelectrochemical methods. The introduced ratio of viologen units was about 60% with respect to the polaron, i.e., one-electron oxidized state localized over five thiophene units.     

A nonequilibrium molecular dynamics method for thermal conductivities based on thermal noise

We developed a nonequilibrium molecular dynamics (NEMD) method for calculating thermal conductivities. In contrast to other NEMD algorithms, here only the heat sink is localized, whereas the heat source can be uniformly distributed throughout the system. The noise due to cutting off the pair forces or to integration errors is such a uniform heat source. In traditional NEMD methods it is normally considered a nuisance factor. The new algorithm accounts for it and uses it. The algorithm is easy to derive, analyse and implement. Moreover, it circumvents the need to calculate energy fluxes. It is tested on the enhanced simple-point charge model for liquid water and reproduces the known thermal conductivity of this model liquid of 0.81 W m(-1) K(-1). It can be generalized to situations, where the thermal noise is replaced by another uniform heat source, or to the inverse situation, where the heat source is localized but the heat sink extends over the entire system.     

Synthesis and nitration of some thieno-fused analogues of the benzo[a]quinolizinium cation

Three thieno-fused analogues of benzo[a]quinolizinium ( 1 ), thieno[3,2-a]- and thieno[2,3-a]quinolizinium 4 and 5 and thiazolo[2,3-a]isoquinolinium ( 6 ), were synthesized by photocyclization of 1-(2-thienylvinyl)pyridinium salts 9a and 9b and 3-styrylthiazolium salt 9c , respectively. The nitration of the compounds 4, 5 , and 6 occurred predominantly at positions 2, 3, and 7, respectively, while the nitro group was introduced into the 8- and 10-positions of 1 in the ratio of 68:32. The nmr and uv spectral properties and reduction potentials of 4–6 were also compared with those of the parent compound 1 .     

Synthesis of Cristobalite Containing Ordered Interstitial Mesopores using Crystallization of Silica Colloidal Crystals

Cristobalite with ordered interstitial dual-sized mesopores was synthesized through the crystallization of silica colloidal crystals composed of monodispersed amorphous silica nanoparticles. An aqueous solution containing both a flux (Na₂O) and a carbon precursor (an aqueous low-molecular weight phenolic resin) was infiltrated into the interstices of silica colloidal crystals. The organic fraction in the nanocomposite was further polymerized and subsequently carbonized in an Ar flow at 750 °C to reinforce the colloidal crystal structure. The thermal treatment resulted in the crystallization of the colloidal crystals into cristobalite while retaining the porous structure. The cristobalite-carbon nanocomposite was calcined in air to remove the carbon and create interstitial ordered mesopores in the cristobalite. The surfaces of crystalline mesoporous silica are quite different from those of various ordered mesoporous silica with amorphous frameworks; thus, the present findings will be useful for a precise understanding and control of the interfaces between the mesopores and silica networks.