Diastereoselective addition of allyltitanocenes to cyclic enones

The reaction of allyltitanocenes with five- to seven-membered cyclic enones proceeded with good to high diastereoselectivity depending on the ring size of enones. The stereochemistry of the major isomers produced by the reaction of cinnamyltitanocene was opposite to that of crotyltitanocene.     

Synthesis, structure and luminescence properties of Cu(ii), Zn(ii) and Cd(ii) complexes with 4'-terphenylterpyridine

The complexes [M(tptpy)(2)](ClO(4))(2) (M = Zn(ii) (1), Cd(ii) (2), and Cu(ii) (3)); tptpy = 4'-[1,1':4',1']terphenyl-4'-yl-[2,2':6',2']terpyridine = 4'-terphenylterpyridine) have been synthesized, structurally characterized by X-ray crystallography and subjected to preliminary luminescence studies. In the crystalline state, all the metal ions have an N(6) coordination sphere of distorted octahedral geometry and the structures of the Zn(ii) and Cd(ii) complexes are isomorphous but differ from that of the Cu(ii) complex, which also differs from the other two in that it is non-emissive. The structure determinations show that aromatic-aromatic interactions involving both the terpyridine heads and the terphenyl tails are important factors influencing the crystalline array. The emission spectra of the Zn(ii) and Cd(ii) complexes are very similar and show a considerable red-shift of the emission maximum compared to that of the free ligand.     

C3-symmetric trisimidazoline-catalyzed enantioselective bromolactonization of internal alkenoic acids

A method for conducting enantioselective bromolactonization reactions of trisubstituted alkenoic acids, using the C(3)-symmetric trisimidazoline 1 and 1,3-dibromo-5,5-dimethyl hydantoin as a bromine source, has been developed. The process generates chiral δ-lactones that contain a quaternary carbon. The results of studies probing geometrically different olefins show that (Z)-olefins rather than (E)-olefins are favorable substrates for the process. The method is not only applicable to acyclic olefin reactants but can also be employed to transform cyclic trisubstituted olefins into chiral spirocyclic lactones. Finally, the synthetic utility of the newly developed process is demonstrated by its application to a concise synthesis of tanikolide, an antifungal marine natural product.     

Structured Catalysts Prepared by Electroless Plating Technique onto a Metal Substrate, for a Wall-Type Hydrogen Production System

This article reviews our works on the structured catalysts for a wall-type hydrogen production system including methanol steam reforming (MSR), CO shift reaction (CO SR) and methanol decomposition (MD). The structured catalysts were copper-based, palladium-based and nickel-based catalysts. Such a series of structured catalysts were prepared by the electroless plating technique that is a novel method for preparing a structured type catalyst onto a metal-substrate. The copper-based catalyst exhibited high performance for MSR and CO SR, the palladium-based catalyst high for MSR, and the nickel-based catalyst high for MD. The catalytic properties of these catalysts were affected by the difference of the plating condition and the pretreatment condition prior to the reaction. In the copper-based catalyst, the reforming and shift activities were enhanced by the oxidation treatment. One of the factors of such activity enhancement by the oxidation was thought to be in close proximity existence of copper and zinc atoms. A lot of monodentate-type formate species having high reactivity was formed on the oxidized catalyst, which would be correlated to the activity enhancement. In the palladium-based catalyst, the reforming activity was improved by the continuous reduction treatment followed by the oxidation. Such continuous pretreatment formed the PdZn alloy species thought to be a reforming site in the surface layer. The decomposition performance of the nickel-based catalyst depended on the ratio of the crystallite size of nickel particles to that of aluminum particles. The electronic influence of zinc and phosphorous components incorporated in the plated layer contributed to the improvement of the selectivity of product.     

One‐Pot/Sequential Native Chemical Ligation Using N‐Sulfanylethylanilide Peptide

N‐Sulfanylethylanilide (SEAlide) peptides were developed with the aim of achieving facile synthesis of peptide thioesters by 9‐fluorenylmethyloxycarbonyl (Fmoc)‐based solid‐phase peptide synthesis (Fmoc SPPS). Initially, SEAlide peptides were found to be converted to the corresponding peptide thioesters under acidic conditions. However, the SEAlide moiety was proved to function as a thioester in the presence of phosphate salts and to participate in native chemical ligation (NCL) with N‐terminal cysteinyl peptides, and this has served as a powerful protein synthesis methodology. The reactivity of a SEAlide peptide (anilide vs. thioester) can be easily tuned with or without the use of phosphate salts. This interesting property of SEAlide peptides allows sequential three‐fragment or unprecedented four‐fragment ligation for efficient one‐pot peptide/protein synthesis. Furthermore, dual‐kinetically controlled ligation, which enables three peptide fragments simultaneously present in the reaction to be ligated in the correct order, was first achieved using a SEAlide peptide. Beyond our initial expectations, SEAlide peptides have served in protein chemistry fields as very useful crypto‐peptide thioesters. DOI 10.1002/tcr.201200007     

Highly diastereoselective construction of acyclic systems with two adjacent quaternary stereocenters by allylation of ketones

Unsymmetrical ketones and allyltitanocenes generated by the desulfurizative titanation of γ,γ-disubstituted allyl phenyl sulfides react under highly diastereoselective construction of adjacent quaternary stereocenters (see scheme; R(L) = large group, R(S) = small group). The title reaction is stereospecific: the anti- and syn-homoallylic alcohols are obtained by the reaction of E- and Z-allylic sulfides, respectively.     

Unprecedented reversible redox process in the ZnMFI-H2 system involving formation of stable atomic Zn(0)

In its element: Zn(2+) at the M7 site of MFI-type zeolites activates H(2), via ZnH and OH species, and leads to Zn(0) species. The Zn(0) species returns to its original state, a Zn(2+) ion, upon evacuation of the zeolite at 873?K (see picture). The formation of the Zn(0) species is supported by DFT calculations.     

Mode change in the self-motion of a benzoquinone disk coupled with a NADPH system

The self-motion of a benzoquinone (BQ) disk on NADPH was investigated as the coupling of an autonomous motor and an enzyme reaction. In the absence of the enzyme reaction, features of motion changed depending on the concentration of NADPH, that is, continuous motion→ intermittent oscillatory motion→ no motion. When the reverse reaction from NADP(+) to NADPH was introduced into the system with the addition of an enzyme reaction, continuous motion changed to intermittent oscillatory motion with small amplitude. The mechanism of this mode change is discussed in relation to the surface tension as a driving force and the time course of UV spectra as a window to the progress of the reaction. Characteristic features of the mode change were qualitatively reproduced by a numerical calculation.     

Electrochemical preparation and characterization of a cobalt oxide–platinum composite with promising capacitive and electrocatalytic features

In the present work, boron-doped diamond polycrystalline films were used as support for direct anodic deposition of the cobalt oxide, and continuous Co₃O₄ coatings with reasonably good conductivity were obtained by appropriately adjusting the deposition charge. Further electrochemical deposition of platinum particles on the oxide substrate enabled the formation of a stable composite with a specific capacitance of ca. 431 F?cm^?3 that compares well with that available with similar materials obtained by non-electrochemical methods. Additional advantages of electrochemically obtained composites are the lower content of noble metal, the uniform distribution of the charge over an extended potential range, and, importantly, the simplicity of the preparation method. It was also found that when deposited on a Co₃O₄ substrate, Pt particles show, besides an enhanced active surface area, an improved catalytic activity for methanol anodic oxidation. This behavior was tentatively ascribed to the presence of a high amount of platinum-oxidized species.