The first regioselective palladium-catalyzed indolization of 2-bromo- or 2-chloroanilines with internal alkynes: a new approach to 2,3-disubstituted indoles

[reaction: see text] The first practical and economical process for synthesis of 2,3-disubstituted indole compounds has been developed with high regioselectivity by palladium-catalyzed indolization of 2-bromo- or chloroanilines and their derivatives with internal alkynes.     

Unexpected, drastic effect of triflic acid on oxidative diacetoxylation of iodoarenes by sodium perborate. A facile and efficient one-pot synthesis of (diacetoxyiodo)arenes

An easy, safe, and effective method for preparing (diacetoxyiodo)arenes from iodoarenes is presented. Addition of trifluoromethanesulfonic acid (triflic acid) as a promoter causes a drastic increase in the yield of (diacetoxyiodo)arenes in the reaction of iodoarenes with sodium perborate. The reaction of the iodoarenes with sodium perborate in acetic acid in the presence of triflic acid at 40-45 degrees C efficiently generates the corresponding (diacetoxyiodo)arenes in high yields within short time.     

Facile synthesis of core‐surface crosslinked nanoparticles by interblock RAFT polymerization

A new, efficient method for synthesizing stable nanoparticles with poly(ethylene oxide) (PEO) functionalities on the core surface, in which the micellization and crosslinking reactions occur in one pot, has been developed. First, amphiphilic PEO‐b‐PS copolymers were synthesized by reversible addition fragmentation chain transfer (RAFT) radical polymerization of styrene using (PEO)‐based trithiocarbonate as a macro‐RAFT agent. The low molecular weight PEO‐b‐PS copolymer was dissolved in isopropyl alcohol where the block copolymer self‐assembled as core‐shell micelles, and then the core‐shell interface crosslink was performed using divinylbenzene as a crosslinking agent and 2,2′‐azobisisobutyronitrile as an initiator. The design of the amphiphilic RAFT agent is critical for the successful preparation of core‐shell interface crosslinked micellar nanoparticles, because of RAFT functional groups interconnect PEO and polystyrene blocks. The PEO functionality of the nanoparticles surface was confirmed by ¹H NMR and FTIR. The size and morphology of the nanoparticles was confirmed by scanning electron microscopy, transmission electron microscopy, and dynamic laser light scattering analysis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis and characterization of a polymer-anchored palladium(II) Schiff base complex and its catalytic efficiency in phosphine-free Sonogashira coupling reactions

A polymer-anchored Pd(II) Schiff base complex has been synthesized by reacting a polymeric amine with 2-pyridinecarboxaldehyde to get the polymer-anchored Schiff base, which was then reacted with palladium acetate. The catalyst was characterized by physicochemical and spectroscopic methods. It shows excellent catalytic activity in the Sonogashira coupling of phenylacetylene with aryl halides using triethylamine as a base and copper iodide as a co-catalyst in water under open air at 70 °C. We have also studied the effects of base and solvent on the coupling reaction. Sonogashira reactions of phenylacetylene with a variety of functionalized aryl halides were performed under the optimized reaction conditions. This catalyst gives excellent yields without the use of phosphine ligands. Further experiments showed that the catalyst can be used five times without much loss in the catalytic activity.     

Sensitive Superoxide Biosensor Based on Silicon Carbide Nanoparticles

Direct electron transfer of immobilized superoxide dismutase (Cu, Zn‐SOD) onto silicon carbide (SiC) nanoparticles displays a pair of well defined and nearly reversible redox peaks with formal potential (E°′) of −0.03 V in pH 7.4. The heterogeneous electron transfer rate constant (k_s) and surface coverage (Γ) of immobilized SOD are 11.0±0.4 s⁻¹ and 1.42×10⁻¹¹ mol cm⁻². Biosensor shows fast amperometric response (3s) with sensitivity and detection limit of 1.416 nA μM⁻¹, 1.66 μM, and 1.375 nA μM⁻¹, 2.1 μM for cathodically or anodically detection of superoxide, respectively. This biosensor also exhibits good stability, reproducibility and long life‐time.     

First Synthesis of Continuous Mesoporous Copper Films with Uniformly Sized Pores by Electrochemical Soft Templating

Although mesoporous metals have been synthesized by electrochemical methods, the possible compositions have been limited to noble metals (e.g., palladium, platinum, gold) and their alloys. Herein we describe the first fabrication of continuously mesoporous Cu films using polymeric micelles as soft templates to control the growth of Cu under sophisticated electrochemical conditions. Uniformly sized mesopores are evenly distributed over the entire film, and the pore walls are composed of highly crystalized Cu.     

Competing forward and reversed chain reactions in one-dimensional molecular line growth on the Si(100)-(2 x 1)-H surface

To explore the role of competing forward and reversed chain reactions in the growth of a one-dimensional (1D) molecular line on the Si(100)-(2 x 1)-H surface, controlled experiments were performed with various alkene molecules by scanning tunneling microscopy (STM) at various temperatures. It was observed that the end dangling bond (DB) of a styrene line, fabricated by a chain reaction on the Si(100)-(2 x 1)-H surface at 300 K, initiated a reverse chain reaction at 400 K, leading to the complete disappearance of the styrene line with zero-order desorption kinetics (rate constant k = 1.17 x 10-2 s-1 at 400 K). In the case of 2,4-dimethylstyrene, the reversed chain reaction was observed even at 300 K. These results suggest that the appearance of a molecular line in an STM image is determined by the rates of competing forward and reversed chain reactions at a given temperature. As predicted, 1D lines formed by the DB-initiated chain reaction of 1-hexene and 1-heptene on Si(100)-(2 x 1)-H were observed at 180 K because of the reduced desorption rate, despite the fact that those molecules showed no line growth at 300 K. These results indicate that the scope of forming 1D molecular lines on the Si(100)-(2 x 1)-H surface with various alkenes is much wider than anticipated in previous studies.     

Dithiolate complexes of manganese and rhenium: X-ray structure and properties of an unusual mixed valence cluster Mn3(CO)6(mu-eta2-SCH2CH2CH2S)3

Treatment of Mn(2)(CO)(10) with 3,4-toluenedithiol and 1,2-ethanedithiol in the presence of Me(3)NO.2H(2)O in CH(2)Cl(2) at room temperature afforded the dinuclear complexes Mn(2)(CO)(6)(mu-eta(4)-SC(6)H(3)(CH(3))S-SC(6)H(3)(CH(3))S) (1), and Mn(2)(CO)(6)(mu-eta(4)-SCH(2)CH(2)S-SCH(2)CH(2)S) (2), respectively. Similar reactions of Re(2)(CO)(10) with 3,4-toluenedithiol, 1,2-benzenedithiol, and 1,2-ethanedithiol yielded the dirhenium complexes Re(2)(CO)(6)(mu-eta(4)-SC(6)H(3)(CH(3))S-SC(6)H(3)(CH(3))S) (3), Re(2)(CO)(6)(mu-eta(4)-SC(6)H(4)S-SC(6)H(4)S) (4), and Re(2)(CO)(6)(SCH(2)CH(2)S-SCH(2)CH(2)S) (5), respectively. In contrast, treatment of Mn(2)(CO)(10) with 1,3-propanedithiol afforded the trimanganese compound Mn(3)(CO)(6)(mu-eta(2)-SCH(2)CH(2)CH(2)S)(3) (6), whereas Re(2)(CO)(10) gave only intractable materials. The molecular structures of 1, 3, and 6 have been determined by single-crystal X-ray diffraction studies. The dimanganese and dirhenium carbonyl compounds 1-5contain a binucleating disulfide ligand, formed by interligand disulfide bond formation between two dithiolate ligands identical in structure to that of the previously reported dimanganese complex Mn(2)(CO)(6)(mu-eta(4)-SC(6)H(4)S-SC(6)H(4)S). Complex 6, on the other hand, forms a unique example of a mixed-valence trimangenese carbonyl compound containing three bridging 1,3-propanedithiolate ligands. The solution properties of 6 have been investigated by UV-vis and EPR spectroscopies as well as electrochemical techniques.     

Sorption and immobilization of cellulase on silicate clay minerals

The interaction of organic molecules with mineral surfaces is a subject of interest in a variety of disciplines. Enzymes are able to be sorbed and immobilized by clay minerals and humic colloids in soil environment. The present study was done to elucidate some aspects of sorption and immobilization of cellulase on soil components by analysis of the sorption, and immobilization of cellulase on Avicel, a soil sample, illite, kaolinite, montmorillonite, and palygorskite. Palygorskite displayed the highest sorption capacity. Sorbents coated with hydroxyaluminum displayed significantly higher capacity than uncoated sorbents. The positive effects of Al(OH)(x) coating on sorption capacities of the different sorbents were not equal. The effect decreased in the order soil > palygorskite > kaolinite > Avicel > montmorillonite > illite. The amount of sorbed cellulase desorbed from external surfaces of soil was quite low (about 16%), especially in coated samples (about 6%). X-ray diffraction analysis of K-montmorillonite and Ca-montmorillonite showed that Al(OH)(x) was intercalated between the montmorillonite layers. Immobilization of cellulase on the sorbents did not result in expansion of their crystal structures. Therefore, it may be concluded that the amount of cellulase immobilized on internal surfaces of the sorbents was negligible.     

Synthesis, structures and reactivity of triosmium clusters containing terminal pyrazines, bridging hydroxy and methoxycarbonyl ligands

Four triosmium carbonyl clusters bearing terminal pyrazines, bridging hydroxy and methoxycarbonyl ligands of general formula [Os₃(CO)₉(μ-OH)(μ-OMeCO)L] (1, L = pyrazine; 2, L = 2-methylpyrazine; 3, L = 2,3-dimethylpyrazine; 4, L = 2,3,5-trimethylpyrazine) were synthesized by the reactions of [Os₃(CO)₁₂] with the corresponding pyrazine derivatives and water in the presence of a methanolic solution of Me₃NO in moderate yields. Compounds [Os₃(CO)₉(μ-OH)(μ-OMeCO)L] react with a series of two electron donor ligands, L′ at ambient temperature to give [Os₃(CO)₉(μ-OH)(μ-OMeCO)L′] (5, L′ = PPh₃; 6, L′ = P(OMe)₃; 7, L′ = ^tBuNC; 8, L′ = C₅H₅N) in good yields by the displacement of the pyrazine ligands. This implies that the pyrazine ligands in 1–4 are relatively labile. Compounds 2, 3, 4, and 8 were characterized by single crystal X-ray diffraction analyses. All the four compounds possess two metal–metal bonds and a non-bonded separation of two osmium atoms defined by Os(1)Os(3), which are simultaneously bridged by OH and MeOCO ligands and a heterocyclic ligand is terminally coordinated to one of the two non-bonded osmium atoms.