bluuebunny/crossref_metadata_2025_split huggingface dataset:
Organocopper Reagents: Substitution, Conjugate Addition, Carbo/Metallocupration, and Other Reactions
Authors: Lipshutz Bruce H. , Sengupta Saumitra 
Published: November 2004

AbstractWell over a decade ago, two reviews were contributed to theOrganic Reactionsseries covering substitution and conjugate addition reactions in organocopper chemistry. Their appearance, which highlighted most of the early work in this field, served not only as a source of invaluable references to original literature reports, but also stimulated a vast number of subsequent studies on the properties and uses of organocopper complexes.The work cited in this chapter, which dates from ca. 1975, concerns in large measure uses of organocopper complexes originating from either catalytic or stoichiometric quantities of a copper(I) halide together with a Grignard (RMgX) or organolithium (RLi) reagent. These combinations form either neutral organocopper reagents RCu (1) or copper(I) monoanionic salts R2CuM (M = Li or MgX), commonly referred to as “lower‐order” species. The latteratecomplexes with lithium as gegenion (2) are also known as “Gilman reagents” in recognition of their origins. Copper(I) cyanide is also an excellent precursor, affording homogeneous mixtures of lower order cyanocuprates RCu(CN)Li, (3), upon treatment with an equivalent of an organolithium. The strength of the CuCN linkage presumably accounts for direct cuprate formation with 1 equivalent of the organolithium, rather than the metathesis that occurs with copper(I) chloride, bromide, or iodide.While use of reagents (1), (2) and (3) alone can be aptly classified as broad‐based and intense, their importance has further encouraged extensive development of variations on these themes (i.e., their composition and reactivity profiles). Reagents (1–3) have been found to be unexpectedly compatible with certain electrophilic additives at low temperatures, which substantially alter their reactivity. Rather than forming (2) from 2 equivalents of the same RLi, different organolithiums can be utilized to give RTRRCuLi, (4), conserving potentially valuable RLi. This scenario raises the question of controlling the selectivity of transfer of the desired ligand RTrather than the anticipated residual (or “dummy”) group RRfrom copper to electrophilic carbon. Fortunately, many solutions to this problem now exist.Admixture of 2RLi (or RTLi + RRLi) with copper(I) cyanide proceeds beyond the stage of (3) to ultimately arrive at copper(I) dianionic complexes5, the so‐called “higher‐order” cyanocuprates. Undoubtedly it is the cyano ligand, with its π‐acidic nature, which enables copper to accept a third negatively charged ligand. Although reagents (5) do not yet share in all of the benefits offered by time in comparison with their lower‐order counterparts, they nicely complement prior art. Moreover, as with species (1–4), they continue to evolve, providing the synthetic community with alternatives for highly selective and efficient means of making key carbon–carbon bonds.
Carbonyl Methylenation and Alkylidenation Using Titanium‐Based Reagents
Authors: Pine Stanley H. 
Published: November 2004

Abstract
Alkylidenation of the carbonyl group of ketones and aldehydes is among the most useful reactions of organic synthesis. The Wittig reaction of phosphoranes is probably the most widely used method of alkylidenation, although a variety of other approaches have been developed to accomplish this transformation.
The observation that titanium‐based reagents can accomplish such a transformation has provided a new approach to alkylidenation. Not only do these reagents accomplish alkylidenation of the carbonyl group of aldehydes and ketones, but they are also effective with esters, lactones, amides, thioesters, and certain other carboxylic acid derivatives. Alkylidenation of the carbonyl group of carboxylic acid derivatives cannot normally be accomplished by the Wittig reaction.
Initial interest in the reaction focused on methylenation using the titanium–aluminum complex known as the Tebbe reagent.
Reactions of the Tebbe reagent with carboxylic esters and observed their conversion to enol ethers in high yield.
Furthermore, the Tebbe reagent was also found to methylenate aldehydes and ketones, sometimes more effectively than the Wittig method. The related titanium metallacycles, which are prepared from the Tebbe reagent and an alkene in the presence of a Lewis base, accomplish similar alkylidenations.
During the same period a still undefined reagent was prepared from zinc, a dihalomethane, and titanium tetrachloride that was shown to methylenate aldehydes and ketones. Modification of this mixture provides a reagent that accomplishes methylenation and alkylidenation of carboxylic acid derivatives. An alternative preparation of this reagent has also received wide use.
Reagents for carbonyl alkylidenation involving titanium–magnesium, zirconium, tantalum, tungsten, molybdenum, boron, and chromium have also been studied, but none has found such broad use in synthesis.
TheBaeyer–VilligerOxidation of Ketones and Aldehydes
Authors: Krow Grant R. 
Published: November 2004

AbstractThe oxidative conversion of alicyclic ketones into lactones with permonosulfuric acid was discovered by Baeyer and Villiger in 1899, and in their honor the general process by which ketones are converted into esters or lactones is now known as the Baeyer–Villiger reaction. The literature on this synthetically useful process has been reviewed comprehensively through 1953 in Volume 9 ofOrganic Reactions, and less comprehensive reviews of the reaction have appeared since then. More recent investigations have led to the development of new synthetic reagents, to improvements in experimental reaction conditions, and to a better understanding of regiochemical and stereochemical aspects of the reaction. Baeyer–Villiger reactions now often can be carried out with functional group chemoselectivity and regiochemical control. Although the recent removal from commerce of 90% hydrogen peroxide and reagents based upon this oxidant are a setback to Baeyer–Villiger reaction methodology, alternative reagents, catalysts, and methods described in this review are available to fill the gaps.The definition of the Baeyer–Villiger reaction is somewhat fuzzy, and can be considered to include both ketones and aldehydes. In addition to the traditional use of organic and inorganic peracids as oxidants, examples of oxygen insertion reactions using hydrogen peroxide, alkyl peroxides, and several metal ion oxidants are considered to fall within the scope of this chapter and are included in the tabular survey.
Preparation of α,β‐Unsaturated Carbonyl Compounds and Nitriles by Selenoxide Elimination
Authors: Reich Hans J. , Wollowitz Susan 
Published: November 2004

AbstractHydrogenation and dehydrogenation reactions play a key role in synthetic organic chemistry. The discoveries that selenium and sulfur substituents could be easily introduced α to a variety of acidifying functional groups, and that these derivatives could be smoothly converted to olefins by selenoxide or sulfoxidesynelimination under mild conditions greatly broadened the range of α,β‐unsaturated carbonyl compounds that could be prepared from their saturated analogs. This chapter covers the preparation from enols or enolates of α‐RSe substituted carbonyl compounds and nitriles and their conversion to olefins by thermolysis of the derived selenoxides. Other procedures for preparing these compounds are discussed in a limited way, and they are included in the tables, but the two‐step dehydrogenation is by far the most frequently used.The rapid acceptance of the selenoxide elimination as a synthetic procedure was the result of two factors: the ease with which many organoselenium compounds could be prepared using readily available, powerful electrophilic and nucleophilic selenium reagents, and the mild conditions (−50° to 40°) under which selenoxides fragment to olefins. Recognized selenoxide eliminations to form olefins were reported in 1967 and 1970, well after the related sulfoxide eliminations had been studied extensively. The application of the sulfoxide and selenoxide eliminations were reported almost simultaneously by several groups in 1973. These reactions have been the subject of several reviews. The principal procedures and reagents for the preparation of the requisite selenium compounds were also identified at that point.Preparations discussed in this chapter areMethod A: Reaction of enolates, enols, enol ethers, and enamines with benzeneselenenyl chloride or bromide, or diphenyl diselenide.Method B: Reaction of enols with seleninylating agents [C6H5Se(O)Cl, (C6H5SeO)2O].Method C: Nucleophilic substitution of α‐halo carbonyl compounds with metal selenolates.Method D: Alkylation of α‐phenylseleno carbonyl compounds and acylation of α‐lithio selenides or selenoxides.
The [2,3]‐Wittig Rearrangement
Authors: NakaI TakeshI , MikamI KoichI 
Published: November 2004

AbstractThe [2,3]‐sigmatropic rearrangement, constitutes a versatile type of bond reorganization which encompasses a number of variations in terms of an atom pair (X, Y) and the type of electron pair on Y (anions, nonbonding electron pairs, or ylides). The Sommelet–Hauser rearrangement is representative.This chapter focuses on the special class of [2,3]‐sigmatropic rearrangement that involves an oxycarbanion (X = oxygen, Y = carbanion) as the migrating terminus. This type of rearrangement is now termed the [2,3]‐Wittig (sigmatropic) rearrangement. The reaction name clearly originates from the fact that this rearrangement formally represents a [2,3]‐sigmatropic version of the classic Wittig rearrangement, a well‐known 1,2‐alkyl shift of oxycarbanions. The [2,3]‐Wittig rearrangement has a rather recent history. Perhaps the first observation of the [2,3]‐Wittig shift is the rearrangement of the allyl fluorenyl ether, which was made in 1960 in the context of mechanistic studies on the Wittig rearrangement. The period of the 1960s to the early 1970s witnessed slow progress with a focus on mechanistic studies mainly of allyl benzyl ether systems. The synthetic power of this carbanion rearrangement as a general method was recognized when Still (1978) and Nakai (1981) established the highly stereoselective variants of the genuine [2,3]‐Wittig rearrangement. In recent years the [2,3]‐Wittig rearrangement has enjoyed widespread application in many facets of organic synthesis. Various aspects of the reaction have been reviewed.This chapter deals with the mechanism, scope and limitation, stereochemistry, and synthetic applications of the [2,3]‐Wittig rearrangement with emphasis on the stereochemical aspects and the synthetic utility. Other hetero [2,3]‐Wittig rearrangements such as thio‐[2,3]‐Wittig variants are not covered.
Glycosylation with Sulfoxides and Sulfinates as Donors or Promoters
Authors: Crich David , Lim Linda B. L. 
Published: November 2004

AbstractThe efficient, stereocontrolled formation of glycosidic bonds is arguably the most fundamental reaction in glycoscience. This chapter surveys four recent distinct glycosylation methods united by the common theme of employing sulfoxides, or closely related sulfinates, either in the glycosyl donor itself or as an integral part of the promoter. In the first method (the sulfoxide method), a glycosyl sulfoxide, the donor, is coupled to an acceptor alcohol by means of an activating agent to give the glycosidic bond. The activating agent is typically triflic anhydride, but other compounds have been used.In the second method (the thiogylcoside method) the donor is thioglycoside. It is activated by means of a promoter derived from the reaction of trifluoromethanesulfonic anhydride and thiosulfinate, a sulfinaminde, or diphenylsulfoxide before coupling to an acceptor alcohol. The third method is dehydrative coupling. This chapter is concerned only with the recent variations in which dehydration is achieved by means of a combination of diaryl sulfoxides and trifluoromethanesulfonic acid. The last method (the oxidative method), involves the direct oxidative glycosylation of glycals. This method differs significantly from the other methods since it does not employ a traditional anomeric derivative as glycosly donor, but derives one from the formal oxidation of glycal.At some time in the activation process, all four methods typically involve the reaction of a sulfoxide, or sulfinate with trifluoromethanesulfonic anhydride. All four methods possess the distinct advantage of using readily prepared, stable gylcosyl donors. Three of them are metal‐free and two of them are capable of coupling to enable the most hindered unreactive alcohols in a matter of minutes at low temperature. These methods are some of the most powerful available for the formation of glycosidic linkages.
Silica Particles: A Novel Drug‐Delivery System
Authors: Barbé C. , Bartlett J. , Kong L. , Finnie K. , Lin H. Q. , Larkin M. , Calleja S. , Bush A. , Calleja G. 
Published: November 2004

AbstractIn recent decades, significant advances in drug‐delivery systems have enabled more effective drug administration. To deliver drugs to specific organs, a range of organic systems (e.g., micelles, liposomes, and polymeric nanoparticles) have been designed. They suffer from limitations, including poor thermal and chemical stability, and rapid elimination by the immune system. In contrast, silica particles offer a biocompatible, stable, and “stealthy” alternative. Bioactive molecules can be easily encapsulated within silica particles by combining sol–gel polymerization with either spray‐drying or emulsion chemistry. Spray‐drying faces challenges, including low yield, surface segregation, and size limitations. In contrast, sol–gel emulsions enable the production of nanoparticles with homogeneous drug distribution, and permit ambient temperature processing, necessary for handling biologicals. Independent control of the size and release rate can be readily achieved. Preliminary in‐vivo experiments reveal enhanced blood stability of the nanoparticles, which, coupled with sustained release of anti‐tumor agents, show good potential for cancer treatment.
Comparison of Pulsed Electrochemical Detection Modes Coupled with Microchip Capillary Electrophoresis
Authors: García Carlos D. , Henry Charles S. 
Published: November 2004

AbstractThere is a need to develop analytical methods that are capable of rapidly measuring small biological markers in the field of metabolomics. Among others, carbohydrates play an important role biologically yet are traditionally hard to detect since they have no chromophore or fluorophore. In the present report, the first application of integrated pulsed amperometric detection (iPAD) coupled with microchip electrophoresis to the analysis of glucose, mannose, sucrose, maltose, glucosamine, lactose, maltotriose and galactose is demonstrated. iPAD is an electrochemical detection mode that can be used for direct detection of carbohydrates, amines and sulfur containing compounds. The effect of different solution parameters, including the buffer concentration, pH and the concentration of SDS on both separation and detection response was analyzed. In addition, a comparison study between PAD and iPAD was performed using glucose, glucosamine, sucrose and maltose as model carbohydrates.
Resistance to Surfactant and Protein Fouling Effects at Conducting Diamond Electrodes
Authors: Shin Dongchan , Tryk Donald A. , Fujishima Akira , Merkoçi Arben , Wang Joseph 
Published: November 2004

AbstractBoron‐doped diamond thin‐film electrodes display negligible fouling effects in the presence of high levels of surface‐active materials, including proteins. Dramatic improvements in the stability of the analyte response (compared to common glassy carbon and carbon paste electrodes) are illustrated using bovine serum albumin (BSA), gelatin, and Triton X‐100 in connection with repetitive square‐wave voltammetric (SWV) measurements. The voltammetric response of ascorbic acid at the diamond electrode exhibits negligible shifts in peak potentials and minimal depressions of current signals over a wide range of surfactant concentrations (0–750 ppm). For example, the diamond electrode exhibited 70, 50 and 60 mV potential shifts for 10 repetitive voltammetric scans in the presence of 100 ppm BSA, gelatin and Triton X‐100, respectively, compared to 120, 190, and 280 mV shifts observed at the glassy carbon electrode. Furthermore, only 4.3 and 6.2% of the initial current decays were observed in the presence of 100 ppm Triton X‐100 and gelatin, respectively (compared to 45.2 and 34.4% diminutions at the glassy carbon electrode). Such improved performance was also confirmed from the SWV measurements of uric acid, dihydroxyphenylacetic acid, and catechol. The greatly improved resistance to surfactant interference reflects the fact that the as‐grown diamond thin film, composed of oxide‐free and hydrogen‐terminated surface, has a relatively lower surface energy and minimal electrostatic attributes, either specific or general, so that little adsorption of surface‐active agents occurs. The topographic AFM images of the diamond electrode surface confirm a negligible BSA fouling effect after repetitive SWV measurements. Such enhanced antifouling features make diamond electrodes very attractive for numerous real‐life electroanalytical applications.
Aroma compounds in Oregon Pinot Noir wine determined by aroma extract dilution analysis (AEDA)
Authors: Fang Yu , Qian Michael 
Published: November 2004

AbstractThe aroma proﬁles of Oregon Pinot Noir wines were investigated with aroma extract dilution analysis (AEDA). The wines were extracted with pentane‐diethyl ether, the aromas were distilled using solvent‐assisted ﬂavour evaporation (SAFE) and separated into acidic/water‐soluble and neutral/basic fractions. In the acidic/water‐soluble fraction, 2‐phenylethanol and 3‐methyl‐1‐butanol showed the highest AEDA values, followed by 2‐methylpropanoic acid, butanoic acid, 2‐methylbutanoic acid, 3‐methylbutanoic acid, 2‐methylpropanol, hexanol, trans‐3‐hexenol, cis‐3‐hexenol, benzyl alcohol, 3‐methylthio‐1‐propanol, 3‐ethylthio‐1‐propanol, linalool and geraniol (all with FD ≥ 64). In the neutral/basic fraction, ethyl 2‐methylpropanoate, ethyl butanoate, 3‐methylbutyl acetate, ethyl hexanoate, and benzaldehyde had very high AEDA values (all with FD ≥ 64), followed by ethyl 3‐methylbutanoate, 3‐methylbutyl 2‐methylpropanoate, ethyl octanoate, ethyl decanoate, benzyl acetate, phenylethyl formate, phenylethyl acetate, ethyl dihydrocinnamate, ethyl anthranilate, 3‐methylthio‐1‐propanal, citronellal, whisky lactone and γ‐nonalactone (all with FD ≥ 16). Overall, the results indicated that there is no single compound that characterizes the aroma of Pinot Noir, and that the characteristic aroma comes from a blend of numerous compounds. Copyright © 2004 John Wiley & Sons, Ltd.
Bradykinin‐induced p42/p44 MAPK phosphorylation and cell proliferation via Src, EGF receptors, and PI3‐K/Akt in vascular smooth muscle cells
Authors: Yang Chuen‐Mao , Lin Meng‐I , Hsieh Hsi‐Lung , Sun Chi‐Chin , Ma Yunn‐Hwa , Hsiao Li‐Der 
Published: November 2004

AbstractIn our previous study, bradykinin (BK) exerts its mitogenic effect through Ras/Raf/MEK/MAPK pathway in vascular smooth muscle cells (VSMCs). In addition to this pathway, the non‐receptor tyrosine kinases (Src), EGF receptor (EGFR), and phosphatidylinositol 3‐kinase (PI3‐K) have been implicated in linking a variety of G‐protein coupled receptors to MAPK cascades. Here, we investigated whether these different mechanisms participating in BK‐induced activation of p42/p44 MAPK and cell proliferation in VSMCs. We initially observed that BK‐ and EGF‐dependent activation of Src, EGFR, Akt, and p42/p44 MAPK and [3H]thymidine incorporation were mediated by Src and EGFR, because the Src inhibitor PP1 and EGFR kinase inhibitor AG1478 abrogated BK‐ and EGF‐dependent effects. Inhibition of PI3‐K by LY294002 attenuated BK‐induced Akt and p42/p44 MAPK phosphorylation and [3H]thymidine incorporation, but had no effect on EGFR phosphorylation, suggesting that EGFR may be an upstream component of PI3‐K/Akt and MAPK in these responses. This hypothesis was supported by the tranfection with dominant negative plasmids of p85 and Akt which significantly attenuated BK‐induced Akt and p42/p44 MAPK phosphorylation. Pretreatment with U0126 (a MEK1/2 inhibitor) attenuated the p42/p44 MAPK phosphorylation and [3H]thymidine incorporation stimulated by BK, but had no effect on Akt activation. Moreover, BK‐induced transactivation of EGFR and cell proliferation was blocked by matrix metalloproteinase inhibitor GM6001. These results suggest that, in VSMCs, the mechanism of BK‐stimulated activation of p42/p44 MAPK and cell proliferation was mediated, at least in part, through activation of Src family kinases, EGFR transactivation, and PI3‐K/Akt. Copyright © 2004 Wiley‐Liss, Inc.
HIV‐1 Tat protein concomitantly down‐regulates apical caspase‐10 and up‐regulates c‐FLIP in lymphoid T cells: A potential molecular mechanism to escape TRAIL cytotoxicity
Authors: Gibellini Davide , Carla Re Maria , Ponti Cristina , Vitone Francesca , Bon Isabella , Fabbri Greta , Grazia Di Iasio Maria , Zauli Giorgio 
Published: November 2004

AbstractIn this study, we showed the existence of a positive correlation between the amount of human immunodeficiency virus‐type 1 (HIV‐1) RNA in HIV‐1 seropositive subjects and the plasma levels of TRAIL. Since it has been previously demonstrated that HIV‐1 Tat protein up‐regulates the expression of TRAIL in monocytic cells whereas tat‐expressing lymphoid cells are more resistant to TRAIL cytotoxicity, we next investigated the effect of Tat on the expression/activity of both apical caspase‐8 and ‐10, which play a key role in mediating the initial phases of apoptosis by TRAIL, and c‐FLIP. Jurkat lymphoblastoid human T cell lines stably transfected with a plasmid expressing wild‐type (HIV‐1) tat gene showed normal levels of caspase‐8 but significantly decreased levels of caspase‐10 at both mRNA and protein levels with respect to Jurkat transfected with the control plasmid or with a mutated (cys22) non‐functional tat cDNA. A significant decrease of caspase‐10 expression/activity was also observed in transient transfection experiments with plasmid carrying tat cDNA. Moreover, c‐FLIPL and c‐FLIPS isoforms were up‐regulated in tat‐expressing cells at both mRNA and protein level in comparison with control cells. Taken together, these results provide a molecular basis to explain the resistance of tat‐expressing Jurkat cells to apoptosis induced by TRAIL and, possibly, to other death‐inducing ligands. © 2004 Wiley‐Liss, Inc.