bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of Substituted Se‐Phenyl Selenocarboxylates from Terminal Alkynes
Authors: Tiecco Marcello , Testaferri Lorenzo , Temperini Andrea , Bagnoli Luana , Marini Francesca , Santi Claudio , Terlizzi Raffaella 
Published: August 2004

AbstractSe‐Phenyl selenocarboxylates have been conveniently prepared from (phenylseleno)acetylenes by treatment with p‐toluenesulfonic acid monohydrate in dichloromethane. This easy conversion is compatible with a broad range of oxygen‐ and nitrogen‐containing functional groups. The Se‐phenyl selenocarboxylates were easily converted into the corresponding esters and amides. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
From N‐Substituted Thioamides to Symmetrical and Unsymmetrical 3,4,5‐Trisubstituted 4H‐1,2,4‐Triazoles: Synthesis and Characterisation of New Chelating Ligands
Authors: Klingele Marco H. , Brooker Sally 
Published: August 2004

AbstractAn improved protocol for the synthesis of N‐substituted pyridine‐2‐thiocarboxamides under the conditions of the Willgerodt−Kindler reaction, employing a catalytic amount of sodium sulfide nonahydrate, has been developed. Following this protocol, eight thioamides carrying aromatic or aliphatic N‐substituents have been prepared in good to excellent yields. Condensation of these thioamides or their S‐alkylated congeners with hydrazides in refluxing 1‐butanol has afforded eight unfused 3,4,5‐trisubstituted 4H‐1,2,4‐triazoles in good yields, including four examples of the otherwise not easily obtainable 4‐alkyl‐3,5‐diaryl‐4H‐1,2,4‐triazoles. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Mechanistic Aspects of the Bismuth‐Catalysed Oxidation of Epoxides to α‐Diketones
Authors: Antoniotti Sylvain , Duñach Elisabet 
Published: August 2004

AbstractThe mechanism of the direct oxidation of 1,2‐disubstituted epoxides to α‐diketones catalysed by BiIII derivatives was examined. The oxidation was carried out in DMSO under dioxygen. Experimental evidence for the various steps of the reaction was obtained from spectroscopic data, isolation of intermediate species, reactions with Bi0, reaction under dinitrogen rather than under dioxygen, measurement of the oxygen consumption, cyclic voltammetry, and oxidations performed in the presence of methyl phenyl sulfoxide. The direct epoxide‐to‐diketone oxidation involves two main reaction steps: a first DMSO‐mediated oxidative ring‐opening of the oxirane ring, and a second Bi‐catalysed oxidation to the α‐diketone by dioxygen. A catalytic cycle is proposed combining the different results. A new alternative preparation of Bi(OTf)3 by oxidative dissolution of Bi0 is also described. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
4,5‐Didehydro‐9‐demethyl‐9‐halo‐5,6‐dihydroretinals and Their 9‐Cyclopropyl and 9‐Isopropyl Derivatives − Simple Preparation of α‐Ionone Derivatives and Pure (all‐E)‐, (9Z)‐ and (11Z)‐α‐Retinals
Authors: Wang Yajie , Lugtenburg Johan 
Published: August 2004

Abstractα‐Ionone and several of its chemically modified derivatives have been prepared in high yield in full isomeric purity by a Wadsworth−Emmons procedure using imino‐phosphonate anion reagents. Starting from α‐ionone, 5‐(2′,6′,6′‐trimethylcyclo‐2′‐hexen‐1′‐yl)‐4‐penten‐2‐yn‐1‐al could be prepared in a high yielding one‐pot procedure. The corresponding (9‐Cl‐, 9‐Br‐ and 9‐I‐α‐ionylidene)acetaldehyde system could be obtained in one step in a quantitative mixture of (9Z) and (all‐E) isomers by 1,4‐nucleophilic addition reactions. The pure (all‐E) and (9Z) isomers could be separated by simple column chromatography. The corresponding [(9Z)‐ and (all‐E)‐9‐demethyl‐9‐fluoro‐α‐ionylidene]acetaldehydes could also be obtained in pure form by simple column chromatography. These α‐ionylidene systems could be easily converted either into the (all‐E)‐4,5‐didehydro‐9‐demethyl‐9‐halo‐5,6‐dihydroretinals or the corresponding (9Z) isomers in two steps. Similar mixtures of the corresponding (9Z,11Z)‐ and (9Z)‐nitriles could be obtained by normal chemistry. The (9Z,11Z) isomer is the main component of this mixture, and could be obtained in pure form. Subsequent reduction with DIBAL‐H and careful workup gave the pure (9Z,11Z)‐9‐haloretinals. These (9Z,11Z) isomers show a similar extreme acid sensitivity to the corresponding 9‐halo‐β‐retinals. α‐Retinal and its 9‐demethyl, 19,19‐ethano and 19,19‐dimethyl derivatives have been prepared in the (all‐E), (9Z), and (11Z) isomeric forms in a similar manner. The corresponding β‐retinal and its 9‐demethyl derivative in the various isomeric forms are known. In this paper the 19,19‐ethano‐ and 19,19‐dimethyl‐β‐retinals in the (all‐E), (9Z), and (11Z) isomeric forms are also reported. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
4,5‐Dihydro‐3H‐benzo[c]azepines from 1,7‐Electrocyclization Reactions of 2‐Aza‐4,5‐benzoheptatrienyllithium Compounds
Authors: Gerdes Klaus , Sagar Pramod , Fröhlich Roland , Wibbeling Birgit , Würthwein Ernst‐Ulrich 
Published: August 2004

AbstractVarious differently substituted (2‐alkenylbenzylidene)amines 4b−d gave, upon deprotonation with amide bases and addition of an electrophile, the respective 4,5‐dihydro‐3H‐benzo[c]azepines 6a−k in moderate to good yields. The imines 4 are easily accessible from 2‐bromobenzaldehyde (1) by Wittig olefination, formylation with DMF, and subsequent condensation with benzylamine. The ring‐closure reaction is interpreted as an anionic 1,7‐electrocyclization reaction involving benzo‐annulated 2‐azaheptatrienyllithium compounds. This reaction, and the subsequent addition of the electrophiles, proceed with excellent diastereoselectivity, determined by the (E) or (Z) configuration of the imines 4b−d. The corresponding allylimines 4e,f do not give ninemembered heterocycles 7, but rather the corresponding 3‐vinyl‐4,5‐dihydro‐3H‐benzo[c]azepines 6l,m. Molecular structures of several compounds 6 in the solid state were determined by X‐ray crystallography, including the structure of a 14‐membered ring dimer 8. High‐level quantum chemical calculations on model anions concerning structures and relative energies of possible intermediates and transition states support the pericyclic mechanism suggested for the ring‐closure reaction. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
A Modular Approach to a New Class of Monodentate Chiral Phosphorus Ligands and Their Application in Enantioselective Copper‐Catalysed Conjugate Additions of Diethylzinc to Cyclohexenone
Authors: Monti Chiara , Gennari Cesare , Steele Rebecca M. , Piarulli Umberto 
Published: August 2004

AbstractA new family of chiral phosphorus ligands (5) for use in enantioselective catalysis have been synthesised. The ligands contain the electron‐poor bis(sulfonyl)diazaphospholidine moiety and possess a highly modular structure which is well suited to the synthesis of a library. A small library (23 members) of ligands 5 was prepared and tested in the enantioselective copper‐catalysed conjugate addition of diethylzinc to cyclohexenone. Complete conversions were obtained with enantiomeric excesses (ee) of up to 75%. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
First Stable O‐Amidinylhydroxylamines and Their Transformations into Sulfenamides by Intramolecular 1,5‐O→S Amine Migration
Authors: Sączewski Franciszek , Kornicka Anita , Gdaniec Maria , Hałasa Rafal , Werel Władyslaw 
Published: August 2004

AbstractThe reaction of 2‐chloro‐4,5‐dihydroimidazole (1) with aliphatic hydroxylamines 2−4 gives O‐amidinylhydroxylamines 5−7 in contrast to the analogous reaction of 1 with N‐arylhydroxylamines in which N‐substitution occurs. A number of thiocarbamoylsulfenamides 8−10 have been prepared by the reaction of 5−7 with carbon disulfide under basic and mild conditions. The key step in the 1,5‐O→S amine migration involves the tandem nucleophilic addition‐electrophilic amination reaction. The intermolecular version of this process using preformed triethylammonium dithiocarbamates gives the corresponding sulfenamides 14−16. Functionalized ethylenediamines 17−19 are obtained by treatment of 8 and 9 with amines. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Stabilised 2,3‐Pyridyne Reactive Intermediates of Exceptional Dienophilicity
Authors: Connon Stephen J. , Hegarty Anthony F. 
Published: August 2004

AbstractThe enhanced dienophilicity of 4‐methoxy, 4‐aryloxy and 4‐thiophenoxy analogues 6−9 of 2,3‐pyridyne (2) relative to 2 itself is reported. The regioselective lithiation of 4‐alkoxy‐ (22, 23 and 25) and 4‐thiophenoxy‐2‐chloropyridine (24) at low temperatures, followed by elimination of lithium chloride affords 4‐alkoxy‐ and 4‐thiophenoxypyridynes, which can be trapped in situ in a [4+2] cycloaddition reaction with furan to give endoxides 28−31 in moderate to good yields (25−58%). In contrast, precursors with a hydrogen (18) or methyl (12) substituent at C‐4 give no evidence for pyridyne formation under these conditions. Attempts to generate 6‐isopropoxy‐2,3‐pyridyne (10) from the low‐temperature lithiation of 2‐chloro‐6‐isopropoxypyridine were unsuccessful due to the instability of the 2‐chloro‐6‐isopropoxy‐5‐lithiopyridine. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Pd/C‐Catalyzed Transfer Reduction of Aryl Chlorides with Sodium Formate in Water
Authors: Arcadi Antonio , Cerichelli Giorgio , Chiarini Marco , Vico Raquel , Zorzan Daniel 
Published: August 2004

AbstractSodium formate catalytic transfer reduction, in the presence of palladium on carbon, accomplishes not only the rapid dehalogenation of aromatic chlorocarbons in water at room temperature, but also the reduction of the aromatic moieties to alicyclic rings at 100 °C. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
The Reaction of 3,4‐Dinitrothiophene with Grignard Reagents: Formation of 2‐(3‐Amino‐4‐nitrothiophen‐2‐yl)phenols
Authors: Bianchi Lara , Dell'Erba Carlo , Maccagno Massimo , Mugnoli Angelo , Novi Marino , Petrillo Giovanni , Severi Elda , Tavani Cinzia 
Published: August 2004

AbstractThe treatment of 3,4‐dinitrothiophene with an aryl Grignard reagent results in the reduction of one nitro group accompanied by the ipso‐substitution of a hydrogen atom by an ortho‐phenolic group on the ring carbon adjacent to the reduced nitro group. A Claisen‐type intramolecular rearrangement is proposed as the pivotal step of a rather complex mechanism, followed by proton‐transfer aromatizing steps. This work shows yet another facet of the variegated reactivity of 3,4‐dinitrothiophene towards nucleophiles. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Synthesis and Characterization of a New Fluorescent Zwitterionic Spirocyclic Meisenheimer Complex of 1,3,5‐Trinitrobenzene
Authors: Al‐Kaysi Rabih O. , Guirado Gonzalo , Valente Edward J. 
Published: August 2004

AbstractIn this communication we present the first stable zwitterionic spirocyclic Meisenheimer compound based on an N→N rearrangement in the reaction between picric acid and diisopropylcarbodiimide. The structure was confirmed by single‐crystal X‐ray diffraction. Furthermore, this compound exhibits interesting fluorescence properties (φf = 0.4−0.5), not shared with a typical Meisenheimer complex, and a fluorescence lifetime (τ = 9.1 ns) in dichloromethane. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
A New Route for the Thermal Isomerization of a Highly Substituted Hexadienyne Derivative
Authors: Berger Harald , Hopf Henning , Dix Ina , Jones Peter G. 
Published: August 2004

AbstractWhereas the thermal isomerization of perphenylbutenyne (11) at 290 °C in toluene leads to the benzannelated semibullvalene derivative 13, pyrolysis at 360 °C furnishes the triphenylnaphthalene 12. The mechanisms of both cycloisomerizations, which presumably proceed via the isobenzene intermediate 14, are discussed. The structure of the rearrangement product 13 was proven by single‐crystal X‐ray analysis. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
The Formal [3+2+1] Cyclisation of Cyclopropylamines with Carboxylic Anhydrides: A Quick Access to Polysubstituted 2,3,3a,4‐Tetrahydro6(5H)‐indolone Ring Systems
Authors: Larquetoux Laurent , Kowalska Justyna A. , Six Yvan 
Published: August 2004

AbstractSeveral 2‐azabicyclo[3.1.0]hexanes were synthesised using the intramolecular version of the Kulinkovich−de Meijere cyclopropanation reaction. Upon heating in the presence of a carboxylic anhydride, the cyclopropane rings of these systems open up to afford vinylogous amides. Depending on the reaction conditions used, the monoacylated compounds may be the major products, or subsequent acylation may take place to afford cyclic diketones. The method is flexible, and it is possible to incorporate different acyl groups in a two‐step sequence. The diketones are easily converted into 2,3,3a,4‐tetrahydro‐6(5H)‐indolone derivatives by intramolecular aldolisation. The products, which are highly functionalised alcohols, are obtained as single diastereoisomers. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
A New Neighbouring‐Group Reaction to Form Pyridopyrrolobenzoxazinediones
Authors: Hamprecht Gerhard , Zimmermann Norbert , Weiß Thomas D. 
Published: August 2004

AbstractThe azaphthalimide 2a is the first phthalimide oxygen found to undergo a neighboring‐group participation reaction with a vicinal N‐phenyl carboxylic acid chloride upon nucleophilic addition with alcohols. Owing to the free rotation of the N‐phenyl moiety, hetero‐anellated benzoxazinedione isomers 3 and 4 are accessible, whereby 3 is preferred to 4 as the pyridine nitrogen in 2a preferentially activates the o‐carbonyl group. Yields of up to 92% were obtained when bases such as HCl acceptors were avoided by heating 2a with alcohols. The reaction is restricted to primary and secondary alcohols, as 2a is nonplanar in respect of the heterocyclic and benzene moiety, which prevents tertiary alcohols attacking the pyrrolidinedione carbonyl group. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Cover Picture: Synthesis and Biological Evaluation of Phorbol‐Resiniferatoxin (RTX) Hybrids (Eur. J. Org. Chem. 16/2004)
Authors: Appendino Giovanni , Bertolino Andrea , Minassi Alberto , Annunziata Rita , Szallasi Arpad , de Petrocellis Luciano , Di Marzo Vincenzo 
Published: August 2004

AbstractThe cover picture shows Euphorbia resinifera Berg and its constituent resiniferatoxin (RTX), a phorboid that acts as an ultrapotent biological analogue of capsaicin, the hot principle of chili pepper and the archetypal vanilloid. Ever since its isolation, interest within the organic community for phorbol has been high on account of its challenging structure, puzzling reactivity, and remarkable bioactivity. Diacyl derivatives of phorbol can act as ultrapotent analogues of the endolipid sn‐1,2‐diacylglycerol (DAG) and show powerful tumour‐promoting properties. The more recent discovery that certain non‐tumour‐promoting phorbol derivatives and phorbol‐related compounds can activate vanilloid receptors of the TRPV1 and TRPV4 type has made phorbol very interesting also for neurosciences. The article by G. Appendino et al. on p. 3413 ff. describes the synthesis of hybrid phorbol‐resiniferatoxin of interest for the study of vanilloid receptors, which discloses some new and unpredictable aspects of the chemistry of phorbol. (Photo courtesy by Prof. Mauro Ballero, University of Cagliari)
Electrochemistry of Nucleic Acids at Solid Electrodes and Its Applications
Authors: de‐los‐Santos‐Álvarez Patricia , Lobo‐Castañón M. Jesús , Miranda‐Ordieres Arturo J. , Tuñón‐Blanco Paulino 
Published: August 2004

AbstractThe knowledge of the redox chemistry of nucleic acids (NA) is of paramount importance in cancer and aging research. Charge migration through DNA is also involved in biologically relevant functions such as DNA damage and repair. In the first part of this article the main aspects of the electrochemistry of nucleic acids at solid electrodes are revised, including redox processes, photoelectroactivity and electrical conductivity. In the second part, an overview of its applications is presented. Methods for electrochemical detection of NA, NA‐based biosensors for detection of nonnucleic acid molecules, studies on the nature and dynamics of interactions and structural conformations of NA, are some applications that take advantage of NA electrochemistry at solid electrodes.
Usefulness of visible dyes for the staining of protein or DNA in electrophoresis
Authors: Jin Li‐Tai , Choi Jung‐Kap 
Published: August 2004

AbstractSince 1993, we have studied visible organic dye stains for protein or DNA to improve methodologies and developed the counterion dye staining method. The method employs two oppositely charged dyes that form an ion‐pair complex in the staining solution. The selective binding of free dye to protein or DNA in the staining solution improves detection sensitivity and speed. It is a rapid and sensitive procedure, involving fixing/staining or staining/quick destaining steps that are completed in 1–1.5 h. The lowest detection limits achieved are 4–8 ng of protein on polyacrylamide gels and ∼10 ng of DNA on agarose gels. The focus of this review is to chronicle the development and current status of the counterion dye staining method for detection of protein or DNA. As an extended application of visible dyes, we also discuss the visible dye staining method for detecting protein on blotting membranes developed in our laboratory.
Detection of tetracysteine‐tagged proteins using a biarsenical fluorescein derivative through dry microplate array gel electrophoresis
Authors: Feldman Galia , Bogoev Roumen , Shevirov Julia , Sartiel Adam , Margalit Ilana 
Published: August 2004

AbstractThe design of an extended‐run 96‐well sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) system and the development of protein detection technology based upon fluorescein derivatives that bind to peptide epitope tags, allows the creation of a truly high‐throughput analysis of protein expression, where less than 20 min are needed to separate proteins and analyze results. We demonstrate the overall capabilities of such a method combination in a complex cell lysate background, while comparing the specific results obtained using a biarsenical fluorescein‐derivative and tetracysteine epitope‐tagged proteins with total protein staining using a fluorescent gel stain and with Western blotting where an anti‐oligohistidine (His) tag antibody has been employed. When applied on purified target proteins without extraneous protein background, the demonstrated sensitivity of the assay on the extended‐run 96‐array precast SDS‐PAGE system allows detection of quantities of tagged protein as low as 1 pmol per band.
Speciation of protein‐bound trace elements by gel electrophoresis and atomic spectrometry
Authors: Ma Renli , McLeod Cameron W. , Tomlinson Kerry , Poole Robert K. 
Published: August 2004

AbstractThe metabolism of trace elements, in particular their binding to proteins in biological systems is of great importance in biochemical, toxicological, and pharmacological studies. As a result there has been a sustained interest over the last two decades in the speciation of protein‐bound metals. Various analytical approaches have been employed, combining efficient separation of metalloproteins by liquid chromatography or electrophoresis with high‐sensitivity elemental detection. Slab‐gel electrophoresis (GE) is a key platform for high‐resolution protein separation, and has been combined with autoradiography and various atomic spectrometric techniques for in‐gel determination of protein‐bound metals. Recently, the combination of GE with state‐of‐the‐art inductively coupled plasma‐mass spectrometry (ICP‐MS), particularly when linked to laser ablation (LA) for direct gel interrogation, has opened up new opportunities for rapid characterization of metalloproteins. The use of GE and atomic spectrometry for the speciation of protein‐bound trace elements is reviewed in this paper. Technical requirements for gel electrophoresis/atomic spectrometric measurement are considered in terms of method compatibilities, detection capability and potential usefulness. The literature is also surveyed to illustrate current status and future trends.
A rapid solid‐phase fluorescence‐based protein assay for quantitation of protein electrophoresis samples containing detergents, chaotropes, dyes, and reducing agents
Authors: Agnew Brian J. , Murray Dustin , Patton Wayne F. 
Published: August 2004

AbstractA new solid‐phase, fluorescence‐based protein assay was developed that quantifies proteins in the presence of detergents, urea and reducing agents (one‐dimensional sodium dodecyl sulfate (1‐D SDS) lysis buffers and urea isoelectric focusing (IEF) buffers). A specially designed 96‐well microplate facilitates application of protein samples to the assay paper and allows easy quantitation of samples using fluorescence microplate readers (top or bottom reading format). Alternatively, stained membranes may be directly scanned using a variety of different laser or charge‐coupled device (CCD)‐based imaging devices with UV or visible imaging capabilities. Since protein is specifically bound to the membrane, contaminants are readily washed away, avoiding interference with the protein measurement. The protein assay has a dynamic range extending from 10 ng to 5 μg of protein per microliter and requires only 1 μL of sample, which is ideal for samples destined for electrophoresis. The protein‐to‐protein variability of staining of ten different proteins was determined to be comparable with that of the bicinchoninic acid (BCA) and Lowry assays (16%). Additionally, the quality of the assay according to Z‐factor analyses is excellent.
Detection of phosphoproteins on electroblot membranes using a small‐molecule organic fluorophore
Authors: Goodman Teresa , Schulenberg Birte , Steinberg Thomas H. , Patton Wayne F. 
Published: August 2004

AbstractA new formulation of the small‐molecule organic fluorophore, Pro‐Q® Diamond dye, has been developed that permits rapid and simple detection of phosphoproteins directly on polyvinylidene difluoride (PVDF) or nitrocellulose membranes (electroblots). Protein samples are first separated by electrophoresis and then electroblotted to membranes, stained and destained, in an analogous manner as typically performed with Amido Black or Ponceau S dye staining of total protein profiles. After staining, blots are imaged using any of a variety of laser‐based gel scanners, xenon‐arc lamp‐based gel scanners or charge‐coupled device (CCD) camera‐based imaging devices equipped with UV trans‐ or epi‐illumination. The uncomplicated and reliable staining protocol delivers results in as little as 1 h and the limit of detection for the stain is typically 2–4 ng of phosphoprotein with a linear dynamic range of approximately 15‐fold. Compared with traditional radiolabeling and antibody‐based approaches, the new method offers significant advantages, including avoidance of radioactivity, no need for expensive antibodies, no requirement for blocking unoccupied sites on the membrane with protein or detergent solutions, no sequence context‐specific binding to phosphorylated amino acid residues and the ability to analyze the native, steady‐state phosphorylation of proteins obtained directly from tissue specimens or body fluids. Pro‐Q Diamond dye binds directly and exclusively to the phosphate moiety, allowing it to detect the broadest spectrum of phosphorylated proteins possible. The stain binds noncovalently to phosphoproteins and is thus fully compatible with matrix‐assisted laser desorption/ionization‐time of flight‐mass spectrometry (MALDI‐TOF‐MS) or Edman sequencing. The blot stain is also compatible with standard colorimetric, fluorogenic, and chemiluminescent detection techniques employed in immunoblotting.