NaY Zeolite Functionalized by Sulfamic Acid/Cu(OAc)2 as a Novel and Reusable Heterogeneous Hybrid Catalyst in Efficient Synthesis of Bis,Tris, and Tetrakis(indolyl)methanes, 3,4‐Dihydropyrimidin‐2(1H)‐ones,and 2‐Aryl‐1H‐benzothiazoles

An efficient acid‐catalyzed synthesis of some bis, tris, and tetrakis(indolyl)methanes, 3,4‐dihydropyrimidin‐2(1H )‐ones, and 2‐aryl‐1H ‐benzothiazoles is reported using NaY zeolite functionalized by sulfamic acid/Cu(OAc )₂ (NaY zeolite‐NHSO₃H /Cu(OAc )₂) in excellent yield. The heterogeneous catalyst has a simple work‐up procedure and could be recycled and reused for six reaction cycles.     

Direct Synthesis of Polycarbonate from Carbon Monoxide and Bisphenol A Using Efficient Pd Complex Catalyst Systems

A direct oxidative carbonylation procedure of Bisphenol A to polycarbonate catalyzed with efficient Pd complex systems has been developed. Pd/2,2′‐bipyridyl complexes possessing 6,6′‐dimethyl substituents, Pd/2,2′‐biquinoline complexes, and dinuclear Pd complexes bridged with a pyridylphosphine ligand were found to give higher molecular weights and yields than conventional Pd catalyst systems. Highest molecular weight (M̄_n = 5 600, M̄_w = 12 900) and yield (86%) were obtained using the Pd/6,6′‐dimethyl‐2,2′‐bipyridyl complex system.     

Efficient One‐pot Synthesis,Antimicrobial and Docking Studies of Some Newer Tetrahydro‐4H‐benzo [1,3‐e]oxazines and Related β‐Acylamino Ketone Derivatives

A concise one‐step procedure was developed for the synthesis of some newer tetrahydro‐4H‐benzo[1,3‐e ]oxazines and β‐acylamino ketone derivatives via condensation of cyclohexanone derivative with different aromatic aldehydes and nitriles in the presence of tetrachlorosilane/zinc chloride (TCS/ZnCl₂) reagent mixture under ambient conditions. Docking studies for the synthesized benzo‐oxazine derivatives were designed and a model of highly active derivatives was mapped for the antimicrobial screening.     

A novel and facile reaction to N6‐alkylated adenosine via benzotriazole as a synthetic auxiliary

The reaction of benzotriazole with aliphatic, aromatic or heteroaromatic aldehyde and adenosine leads to a benzotriazole adduct which is reduced with sodium borohydride to the corresponding N⁶‐alkylated adenosine derivatives. This procedure is also utilized in a new route to N⁶‐(3‐iodobenzyl)adenosine‐5′‐N‐methyluronamide (IB‐MECA) which is considered an important adenosine agonist at A₃ adenosine receptors.     

Ruthenium‐Catalyzed meta‐Selective CH Bromination

The first example of a transition‐metal‐catalyzed, meta‐selective C? H bromination procedure is reported. In the presence of catalytic [{Ru(p‐cymene)Cl₂}₂], tetrabutylammonium tribromide can be used to functionalize the meta C? H bond of 2‐phenylpyridine derivatives, thus affording difficult to access products which are highly predisposed to further derivatization. We demonstrate this utility with one‐pot bromination/arylation and bromination/alkenylation procedures to deliver meta‐arylated and meta‐alkenylated products, respectively, in a single step.     

Metallo‐supramolecular block copolymer micelles: Improved preparation and characterization

Micelles prepared from amphiphilic block copolymers in which a poly(styrene) segment is connected to a poly(ethylene oxide) block via a bis‐(2,2′:6′,2″‐terpyridine‐ruthenium) complex have been intensely studied. In most cases, the micelle populations were found to be strongly heterogeneous in size because of massive micelle/micelle aggregation. In the study reported in this article we tried to improve the homogeneity of the micelle population. The variant preparation procedure developed, which is described here, was used to prepare two “protomer”‐type micelles: PS₂₀‐[Ru]‐PEO₇₀ and PS₂₀‐[Ru]‐PEO₃₇₅. The dropwise addition of water to a solution of the compounds in dimethylformamide was replaced by the controlled addition of water by a syringe pump. The resulting micelles were characterized by sedimentation velocity and sedimentation equilibrium analyses in an analytical ultracentrifuge and by transmission electron microscopy of negatively stained samples. Sedimentation analysis showed virtually unimodal size distributions, in contrast to the findings on micelles prepared previously. PS₂₀‐[Ru]‐PEO₇₀ micelles were found to have an average molar mass of 318,000 g/mol (corresponding to 53 protomers per micelle, which is distinctly less than after micelle preparation by the standard method) and an average hydrodynamic diameter (d_h) of 18 nm. For PS₂₀‐[Ru]‐PEO₃₇₅ micelles, the corresponding values were M = 603,000 g/mol (31 protomers per micelle) and d_h = 34 nm. The latter particles were found to be identical to the “equilibrium” micelles prepared in pure water. Both micelle types had a very narrow molar mass distribution but a much broader distribution of s values and thus of hydrodynamic diameters. This indicates a conformational heterogeneity that is stable on the time scale of sedimentation velocity analysis. The findings from electron microscopy were in disagreement with those from the sedimentation analysis both in average micelle diameter and in the width of the distributions, apparently because of imperfections in the staining procedure. The preparation procedure described also may be useful in micelle formation from other types of protomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4458–4465, 2004     

Ruthenium‐Catalyzed meta‐Selective C?H Bromination

The first example of a transition‐metal‐catalyzed, meta‐selective C H bromination procedure is reported. In the presence of catalytic [{Ru(p‐cymene)Cl₂}₂], tetrabutylammonium tribromide can be used to functionalize the meta C H bond of 2‐phenylpyridine derivatives, thus affording difficult to access products which are highly predisposed to further derivatization. We demonstrate this utility with one‐pot bromination/arylation and bromination/alkenylation procedures to deliver meta‐arylated and meta‐alkenylated products, respectively, in a single step.     

Utilization of Nucleotide Probes in PCR‐ELISA Procedure for the Quantitative Determination of Plasmodium Falciparum DNA in Malaria

Abstract

The research work reported herein is the development of a simple and specific quantitative procedure for the determination of P. falciparum DNA in malaria that involves the direct detection of the highly 42‐kDa conserved C‐terminal regiopn of P. falciparum merozoite surface protein gene (MSP1 ₄₂ gene). This procedure entails the amplification of the MSP1 ₄₂ gene by using the PCR technique in the presence of digoxigenin‐11‐dUTP and the synthesis of the specific biotin label nucleotide probes directed to the MSP1 ₄₂ gene. These specific probes are then used in the Enzyme Linked Immunosorbent Assay (ELISA) for the quantitative determination of the MSP1 ₄₂ gene which leads to the quantitative determination of P. falciparum DNA in malaria for quantitative diagnostic purpose. The P. falciparum malaria diagnostic results obtained from a small number of 18 whole blood samples show that the present quantitative PCR‐ELISA procedure allows the quantitative determination of P. falciparum DNA in malaria with a sensitivity and specificity over to those of the current standard microscopic examination. This quantitative PCR‐ELISA procedure is not only important for quantitative P. falciparum malaria diagnosis but also useful for monitoring the efficacy of any existing anti‐malarial drug as well as for testing the efficacy of any malaria vaccine.     

Natural and Synthetic Xanthones as Monoamine Oxidase Inhibitors: Biological Assay and 3D‐QSAR

Fifty‐nine xanthones (=9H‐xanthen‐9‐ones) of natural or synthetic origin were investigated for their inhibitory activity toward monoamine‐oxidase A (MAO‐A) and MAO‐B. The compounds demonstrated reversible, time‐independent activities, with selectivity toward MAO‐A. The most active inhibitor had an IC₅₀ of 40 nM . Electron absorption spectroscopy revealed the formation of a 1 : 1 charge‐transfer complex between lumiflavine and xanthones. 3D‐QSAR Studies according to the CoMFA/GOLPE procedure provided information on the relationship between steric and electrostatic fields and MAO‐A inhibition. The ALMOND procedure yielded additional topographical information on structural factors favoring activity.     

Rapid Synthesis of 2‐Alkanol‐substituted Pyrrolo[2,3‐b]quinoxalines from Propargylic Alcohols via Copper‐free Sonogashira Coupling Reaction at Room Temperature

A practical and efficient procedure is established for the synthesis of 2‐alkanol‐substituted pyrrolo[2,3‐b]quinoxalines by the reaction of N‐alkyl‐3‐chloroquinoxaline‐2‐amines with propargylic alcohols. The reaction is carried out in the absence of any copper salt but in the presence of a catalytic amount of Pd(PPh₃)₂Cl₂ at room temperature. The Sonogashira coupling reaction step in this procedure is fast, producing clean products with high yields without contamination by unwanted homocoupling Glaser reaction products. The synthesized pyrroloquinoxaline derivatives are also screened against the three bacterial strains Micrococcus luteus, pseudomonas aeruginosa, and Bacillus subtilis.     

Rapid and Scalable Access to Sequence‐Controlled DHDM Multiblock Copolymers by FLP Polymerization

An immortal N‐(diphenylphosphanyl)‐1,3‐diisopropyl‐4,5‐dimethyl‐1,3‐dihydro‐2H‐imidazol‐2‐imine/diisobutyl (2,6‐di‐tert‐butyl‐4‐methylphenoxy) aluminum (P(NIⁱPr)Ph₂/(BHT)AlⁱBu₂)‐based frustrated Lewis pair (FLP) polymerization strategy is presented for rapid and scalable synthesis of the sequence‐controlled multiblock copolymers at room temperature. Without addition of extra initiator or catalyst and complex synthetic procedure, this method enabled a tripentacontablock copolymer (n=53, k=4, dp_n=50) to be achieved with the highest reported block number (n=53) and molecular weight (M_n=310 kg mol^?1) within 30 min. More importantly, this FLP polymerization strategy provided access to the multiblock copolymers with tailored properties by precisely adjusting the monomer sequence and block numbers.     

Diels-Alder Reactions of N-Functionalized Acryloyl α-Pyrrolidone Derivatives Using FeCl3·6H2O as an Efficient Catalyst under Solvent-free Conditions

Diels-Alder reactions of N-functionalized acryloyl α-pyrrolidone derivatives were investigated, which were catalyzed by FeCl3·6H2O as an efficient catalyst under solvent-free conditions at room temperature. The corresponding cycloadducts with functionalized-pyrrolidone were prepared in high yield with high stereoselectivity by a green chemistry procedure. N-Functionalized acryloyl pyrrolidone derivatives, a kind of pyrrolidone-functionalized chelating α,β-unsaturated ketone usable as a dienophile in Diels-Alder reaction, were synthesized by N-acylation procedure in ionic liquid as a novel synthetic method.     

Linear‐Hyperbranched Amphiphilic AB Diblock Copolymers Based on Polystyrene and Hyperbranched Polyglycerol

Summary: A convenient three‐step strategy has been developed for the preparation of well‐defined amphiphilic, linear‐hyperbranched block copolymers by hypergrafting. The synthetic procedure is based on a combination of carbanionic polymerization with the alkoxide‐based, controlled ring‐opening multibranching polymerization of glycidol. A linear AB diblock copolymer polystyrene‐block‐polybutadiene (PS‐b‐PB) with narrow polydispersity was obtained by anionic copolymerization. Subsequent hydroxylation by hydroboration led to PS₅₀₈‐b‐(PB‐OH)₅₆, used as macroinitiator for the polymerization of glycidol under slow monomer addition conditions.

Structure of the linear‐hyperbranched amphiphilic AB diblock copolymer PS₅₀₈‐b‐(PB₅₆‐hg‐PG_x) and an AFM micrograph of its micellar core–shell structure observed after solution casting.     

Voltammetry as a Virtual Potentiometric Sensor in Modelling of a Metal/Ligand System and Refinement of Stability Constants. Part 2

A mathematical conversion of data from nonequilibrium and dynamic voltammetric techniques (direct‐current‐sampled (DC) and differential‐pulse (DP) polarography) into potentiometric, free‐metal‐ion sensor‐type data is described and employed in the study of Bi^III complexes with the ligand picolinic acid (=pyridine‐2‐carboxylic acid) (labile and dynamic metal/ligand system). A novel procedure that allows evaluation of experimental data collected at very low pH values (acid‐base titration) is proposed. Software ESTA dedicated to potentiometry was successfully employed in the refinement operations performed with virtual potentiometric (VP) data obtained from DC and DP polarography, the latter being performed at fixed pH (ligand titration) as well as at fixed [L_T]/[M_T] ratio (acid‐base titration). It was possible to refine stability constants either separately from VP‐DC or VP‐DP, or simultaneously from any combination of VP‐DC and VP‐DP obtained from ligand and/or acid‐base titrations. The concept of VP‐DC or VP‐DP is employed for the first time in the study of an unknown Bi^III/picolinic acid/OH system, and numerous documented and possible advantages are discussed. Five complexes of bismuth, ML, ML₂, ML₃, ML₄, and ML₃(OH) and their stability constants (as log β) 7.48±0.01, 13.94±0.01, 18.10±0.04, 20.47±0.25, and 26.65±0.03, respectively, are reported at 0.5M (Na,H)NO₃ ionic strength and T 298 K. The proposed procedure can be easily utilized also by non‐electrochemists who are interested in, e.g., ligand‐design strategies.     

Polypyrrole/Fe3O4/CNT as a recyclable and highly efficient catalyst for one‐pot three‐component synthesis of pyran derivatives

Polypyrrole (PPY)/Fe₃O₄/CNT has been synthesized and characterized by FT‐IR, TEM and SEM techniques and its catalytic activity has been evaluated in the synthesis of several series of pyran derivatives. Tetrahydrobenzo[b]pyranes, 4H‐pyran‐3‐carboxylates, 4H,5H‐pyrano[3,2‐c]chromenes and dihydropyrano[2,3‐c]pyrazoles have been successfully prepared from one‐pot three‐component condensation of aldehyde, malononitrile and active methylene‐containing compounds (dimedone /ethyl acetoacetate/4‐hydroxycoumarin/3‐methyl‐2‐pyrazoline‐5‐one) using PPY/Fe₃O₄/CNT as a new and reusable heterogeneous catalyst. The present method offer several advantages such as; high yields of products, short reaction times, easy work‐up procedure and easy separation of the catalyst from the reaction mixture due to its magnetic character. Furthermore, chemoselective synthesis of bis‐benzo[b]pyran from terephthalaldehyde can be achieved by this method.     

ZrCl4/TMSCl as an Efficient Catalyst for Synthesis of 4,6‐Substituted 2‐Alkylthio‐6H‐1,3‐thiazines

4,6‐Substituted‐2‐alkylthio‐6H‐1,3‐thiazines were synthesized by the reaction of S‐alkyl dithiocarbamates and α, β‐unsaturated ketones in the presence of ZrCl₄/TMSCl. The procedure is simple and efficient and gives good to high yields of products.     

无溶剂条件下硒酚对末端环氧化合物的开环反应及其在1,3-噁唑烷-2-酮衍生物合成中的应用

Regioselective ring-opening reactions of 1,2-epoxides with ArSeH catalyzed by Ti（O^tPr）4 under solvent-free conditions were investigated. A variety of β-hydroxyselenides were obtained in excellent yields of 90%-97% and regioselectivities by a simple, atom economic and environment-friendly procedure. Several N-tosyl- 1,3-oxazolidin-2-ones were prepared starting from the corresponding 1,2-epoxides and ArSeH by a one-pot three-step procedure.     

A Sequential Method to Prepare Polymorphs and Solvatomorphs of [Fe(1,3‐bpp)2](ClO4)2⋅nH2O (n=0, 1, 2) with Varying Spin‐Crossover Behaviour

Two polymorphs of the spin crossover (SCO) compound [Fe(1,3‐bpp)₂](ClO₄)₂ ( 1 and 2 ; 1,3‐bpp=2‐(pyrazol‐1‐yl)‐6‐(pyrazol‐3‐yl)pyridine) were prepared using a novel, stepwise procedure. Crystals of 1 deposit from dry solvents, while 2 is obtained from a solid‐state procedure, by sequentially removing lattice H₂O molecules from the solvatomorph [Fe(1,3‐bpp)₂](ClO₄)₂?2 H₂O ( 2 ?2 H₂O), using single‐crystal‐to‐single‐crystal (SCSC) transformations. Hydrate 2 ?2 H₂O is obtained through the same reaction as 1 , now with 2.5 % of water added. Compounds 2 and 2 ?2 H₂O are unstable in the atmosphere and absorb or lose one equivalent of water, respectively, to both yield the stable solvatomorph [Fe(1,3‐bpp)₂](ClO₄)₂?H₂O ( 2 ?H₂O), also following SCSC processes. The four derivatives have been characterised by single‐crystal X‐ray diffraction (SCXRD). Furthermore, the homogeneity of the various compounds as well as their SCSC interconversions have been confirmed by powder X‐ray diffraction (PXRD). Polymorphs 1 and 2 exhibit abrupt SCO behaviour near room temperature with T_1/2↑=279/316 K and T_1/2↓=276/314 K (near 40 K of shift) and different cooperativity.     

Application of the monomer reactivity ratios to the kinetic‐model discrimination and the solvent‐effect determination for the styrene/acrylonitrile monomer system

The impact of reactivity ratios determined with the Nelder and Mead simplex method on the kinetic‐model discrimination and the solvent‐effect determination for the styrene/acrylonitrile monomer system was investigated. For the monomer system, the penultimate unit effect was inversely proportional to the polarity of the solvent: acetonitrile < N,N‐dimethylformamide < methyl ethyl ketone < toluene. Quantitatively, the penultimate unit effect could be correlated with an absolute value of the difference between the standard deviation of the reactivity ratios determined for the terminal and penultimate models. By application of the F test, the penultimate model was justified for copolymerization in toluene. The conclusion was less certain for polymerization in methyl ethyl ketone. With a scanning procedure based on the simplex method, it was found that an equivalent representation of the copolymer‐composition data could be achieved with multiple sets of penultimate‐model reactivity ratios. However, the relationship between the triad‐sequence distribution and copolymer composition depended on the reactivity‐ratio set chosen for the microstructure determination. The microstructure calculated with the penultimate‐model reactivity ratios determined with the simplex method from the initial guess (r₁₁ = r₁, r₂₁ = 1/r₂, r₂₂ = r₂, r₁₂ = 1/r₁) did not obey the general “bootstrap effect” rule. This observation still requires some theoretical interpretation. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 846–854, 2000     

The heteroscorpionate ligand 2,2‐bis(3,5‐dimethylpyrazol‐1‐yl)‐1,1‐diphenylethanol and an easy preparation of its tungsten complex

The heteroscorpionate ligand 2,2‐bis(3,5‐dimethylpyrazol‐1‐yl)‐1,1‐diphenylethanol, C₂₄H₂₆N₄O, features in the solid state an intramolecular O—H…N hydrogen bond. A heteroscorpionate tungsten complex, cis‐[2,2‐bis(3,5‐dimethylpyrazolyl)‐1,1‐diphenylethanolato]chloridodioxidotungsten(VI) tetrahydrofuran monosolvate, [W(C₂₄H₂₅N₄O)ClO₂]·C₄H₈O, was prepared by the simple mixing of solutions of the ligand and WOCl₄ in tetrahydrofuran. The tungsten complex was isolated after standing for several weeks. The complex exhibits a κ³N,N′,O‐coordination of the ligand. This simple synthetic procedure allows access to the cis isomer in high yield without additional purification steps. The Hirshfeld surface analysis shows a change of the intermolecular contacts due to the coordination of the WO₂Cl unit with the ligand molecule.