Highly efficient and enantioselective cyclopropanation of styrene with diazoacetates using a new copper-(Schiff-base) catalyst

A new copper-(Schiff-base) complex, derived from (S)-2-amino-1,1-di(3,5-di-t-butylphenyl)propanol, 2-hydroxy-5-nitrobenzaldehyde and copper acetate monohydrate, was used as an efficient catalyst for the cyclopropanation of styrene with diazoacetates, affording ees of up to 98%. (C) 2000 Elsevier Science Ltd. All rights reserved.

Control of cocklebur seed germination by nitrogenous compounds : Nitrite, nitrate, hydroxylamine, thiourea, azide and cyanide

Germination of non-dormant upper cocklebur (Xanthium pinsylvanicum Wallr.) seeds was stimulated by not only CS(NH2)2 but also NH2OH, KCN and NaN3. This stimulation was not via the enhancement of aerobic C2H4 production. NH2OH, KCN and NaN3 in certain concentrations promoted the initial growth of axial and/or cotyledonary parts, but the degree of growth promotion by NH2OH, NaN3 and KCN was slight compared with that by CS(NH2)2. As in the case of CS(NH2)2, however, the germinationstimulating effect of NH2OH disappeared rapidly as the preceding imbibition period was prolonged. In contrast, KCN and NaN3 were still effective in stimulating the germination of aged seeds maintained on a water substratum, as previously seen with anaerobiosis. Anaerobic induction was enhanced not only by NaN3 and KCN but also by NH2OH, KNO3, KNO2 CO(NH2)2 and CS(NH2)2 applied during the anaerobic treatment, but without causing an increase in anaerobic production of C2H4. Furthermore, KCN and NaN3, given prior to the anaerobic treatment acted additively with anaerobic induction. The germination-stimulating actions of nitrogenous compounds are discussed in comparison with those of C2H4 and anaerobiosis.

Preparation and characterization of a novel macrocyclic ligand—dinitro-tetraazacyclotetradeca-tetraene—and application as a highly selective extractant for copper(II)

A novel tetraaza macrocyclic Schiff base ligand, 6,13-dinitro-5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,5,7,-12-tetraene, was prepared and its copper(II) and nickel(II) complexes were characterized. This ligand was found to be an excellent extractant for copper(II).

Calibration of a solid-state copper ion-selective electrode in cupric ion buffers containing chloride

It is shown that near-Nernstian calibration slopes can be obtained with a Cu1.8Se electrode in a range of cupric ion buffers in spite of a high chloride content. Best results are obtained with the ligands ethylenediamine, glycine and histidine. The onset of cupric ion toxicity towards marine organisms falls within the pCu calibration range obtained with glycine, and the Cu1.8Se electrode could, therefore, be useful for monitoring cupric ion activity in bioassays in sea-water media.

The Development of a Marine Natural Product-based Antifouling Paint

Problems with tin and copper antifouling compounds have highlighted the need to develop new environmentally friendly antifouling coatings. Bacteria isolated from living surfaces in the marine environment are a promising source of natural antifouling compounds. Four isolates were used to produce extracts that were formulated into ten waterbased paints. All but one of the paints showed activity against a test panel of fouling bacteria. Five of the paints were further tested for their ability to inhibit the settlement of barnacle larvae, Balanus amphitrite, and algal spores of Ulva lactuca, and for their ability to inhibit the growth of U. lactuca. Two paints caused a significant decrease in the number of settled barnacles. One paint containing extract of Pseudomonas sp. strain NUDMB50-11, showed excellent activity in all assays. The antifouling chemicals responsible for the activity of the extract were isolated, using bioassay guided fractionation, and their chemical structures determined.

Efficient One-Pot Synthesis of Highly Substituted Thiophene Library from 1,3-Dicarbonyl Compounds

A faccile and efficient one-pot synthesis of highly substituted thiophenes has been developed and employed for the preparation of a small focused library. Treatment of 1,3-dicarbonyl compounds 1 with CS2 in the presence of K2CO3 in DMF at room temperature, followed by stepwise addition of alkyl bromides 2 and methylene active bromides 3, provided via intramolecular cyclization 2,3,4,5-tetrasubstituted thiophenes 4 in yields of 77-94%. This protocol, combining construction and modification of the thiophene ring, increases the structural diversity of final products from readily available materials. A mechanism for the one-pot synthesis of thiophenes of type 4 has been proposed. A small focused library of thiophenes is prepared using the sequential addition of reagents to achieve unique substitution in the 2 and 5 position of the thiophene ring

Syntheses, structures and reactions of a series of beta-diketiminatoyttrium compounds

This paper describes the synthesis and selected reactions of a series of crystalline mono(beta-diiminato) yttrium chlorides 3a, 3b, 4a, 4b, 5a, 5b, 5c and 9. The X-ray structure of each has been determined, as well as of [YCl(L-4)(2)] (6), [Y(L-1)(2)OBut] (7) and [Y{CH(SiMe3)(2)}(thf)(mu-Cl)(2)Li(OEt2)(2)(mu-Cl)](2) (8).

An Efficient Ullmann-Type C-O Bond Formation Catalyzed by an Air-Stable Copper(I)-Bipyridyl Complex

An efficient O-arylation of phenols and aliphatic alcohols with aryl halides was developed that uses an air-stable copper(I) complex as the catalyst. This arylation reaction can be performed in good yield in the absence of Cs2CO3. A variety of functional groups are compatible with these reaction conditions with low catalyst loading levels.

Utilizing a CdTe quantum dots-enzyme hybrid system for the determination of both phenolic compounds and hydrogen peroxide

In this paper, we attempt to construct a simple and sensitive detection method for both phenolic compounds and hydrogen peroxide, with the successful combination of the unique property of quantum dots and the specificity of enzymatic reactions. In the presence Of H2O2 and horseradish peroxidase, phenolic compounds can quench quantum dots' photoluminescence efficiently, and the extent of quenching is severalfold to more than 100-fold increase. Quinone intermediates produced from the enzymatic catalyzed oxidation of phenolic compounds were believed to play the main role in the photoluminescence quenching.

Separation of ternary systems of hydrophilic ionic liquid with miscible organic compounds by RPLC with refractive index detection

A rapid and simple analytical method was developed for the simultaneous and quantitative determination and separation of hydrophilic imidazolium ionic liquids (ILs) (1-butyl-3-methylimidazolium chloride, [C(4)mim]Cl; 1-hexyl-3-methylimidazolium chloride, [C(6)mim]Cl; 1-octyl-3-methylimidazolium chloride, [C(8)mim]Cl; 1-allyl-3-methylimidazolium chloride, [Amim]Cl; or 1-allyl-3-methylimidazolium bromide, [Amim]Br) with miscible ethyl acetate and EtOH and their mixtures using reverse phase liquid chromatography coupled with refractive index detection (RPLC-RI). The influence of 60 to 100% (volume percentage) methanol in the mobile phase on the IL systems ([C(4)mim]Cl, [C(6)mim]Cl, [C(8)mim]Cl, [Amim]Br, or [Amim]Cl)-ethyl acetate-EtOH was investigated.

Density functional study on the reaction mechanism of palladium-catalyzed addition of cyanoboranes to Alkynes

The B3LYP hybrid density functional method has been carried Out to Study theoretically the mechanisin of Pd(0)-catalyzed alkyne cyanoboration reaction. Both the intermolecular and intramolecular alkyne cyanoboration reactions were studied. For each reaction, three paths were proposed. In path A of each reaction, the first step is B-CN bond oxidative addition to bisphosphine complex Pd(PH3)(2), in path B of each reaction, the first step is alkyne coordination to bisphosphine complex Pd(PH3)2, and in path C of each reaction, the first step is the PH3 dissociation front Pd(PH3)2 to form monophosphine complex Pd(PH3) For both reactions, path B is favored.

Influence of gate dielectrics on charge transport in copper phthalocyanine thin-film transistors

Copper phthalocyanine organic thin-film transistors (OTFTs) were fabricated with top-gate geometry and the effects of different gate dielectrics on the transport proper-ties in OTFTs were studied. The mobility was found to be gate voltage dependent and the results showed that besides the charge density in the accumulation layer, the energetic disorder induced by gate dielectrics played an important role in determining the field-effect mobility in OTFTs.

Fabrication of an integrated pixel with an organic light-emitting diode driven by copper phthalocyanine organic thin film transistors

An organic integrated pixel with organic light-emitting diodes (OLEDs) driven by organic thin film transistors (OTFTs) is fabricated by a greatly simplified processing. The OTFTs are based on copper phthalocyanine as the active medium and fabricated on indium-tin-oxide (ITO) glass with top-gate structure, thus an organic integrated pixel is easily made by integrating OLED with OTFT. The OTFTs show field-effect mobility of 0.4 cm(2) /Vs and on/off ratio of 10(3) order. The OLED is driven well and emits the brightness as large as 2100cd/m(2) at a current density of 14.6 mu A/cm(2) at -19.7 V gate voltage. This simple device structure is promising in the future large-area flexible OLED displays.