bluuebunny/crossref_metadata_2025_split huggingface dataset:
TheStille Reaction
Authors: Farina Vittorio , Krishnamurthy Venkat , Scott William J. 
Published: April 2004

AbstractExamples of the palladium‐catalyzed coupling of organotin compounds with carbon electrophiles were first reported in 1977 by Kosugi, Shimizu, and Migita. The first study by Stille appeared in 1978. The early work of Beletskaya, using “ligandless” catalysts in cross‐coupling reactions, also often employed organostannanes. In recognition of Stille's comprehensive synthetic and mechanistic studies, this coupling is now referred to as the Stille reaction.R1is typically an unsaturated moiety (e.g., vinyl, aryl, heteroaryl, alkynyl, allyl) or less often an alkyl group, and R2, the nontransferable ligand, is almost always butyl or methyl. Electrophiles participating in the coupling include halides (almost always bromides or iodides) and sulfonates (most often used are the triflates). Other leaving groups have been used in special cases.The Stille reaction belongs to the larger family of palladium‐ and nickel‐catalyzed cross‐coupling reactions which features, e.g., organomagnesium, organozinc, organoboron, and organosilicon reagents.Organotin reagents are air‐ and moisture‐stable organometallics, and can be conveniently purified and stored. Since they do not react with most common functional groups, the use of protecting groups is almost always unnecessary in conjunction with the Stille reaction. This is a very unusual and attractive feature for an organometallic process. Also, the reaction is often neither air nor moisture sensitive. In some cases, water and oxygen have actually been shown to promote the coupling. Although the reaction as initially described by Stille is often carried out under rather drastic conditions (temperatures of ≥100° are not uncommon), newly developed ligand11and the addition of copper(I) salts have solved some of the problems associated with low reactivity. The utility and mildness of the Stille reaction are demonstrated by its frequent use in the final stages of complex natural product syntheses.This chapter attempts a critical and comprehensive coverage of the reaction scope. Mechanistic description of the reaction is rather brief, and the reader is referred to the pertinent literature for a more detailed analysis. All of the relevant literature is covered up to the end of 1994. The reaction was reviewed by Stille in 1986, and by Mitchell in 1992; a rather comprehensive account by Farina and Roth has appeared more recently. Developments that occurred in 1995, as this work was in progress, and that were deemed important were incorporated as much as possible in this review.
The Catalyzed α‐Hydroxyalkylation and α‐Aminoalkylation of Activated Olefins (The Morita—Baylis—Hillman Reaction)
Authors: Ciganek Engelbert 
Published: April 2004

AbstractIn a patent application published in 1972, Baylis and Hillman reported the reaction of acetaldehyde with ethyl acrylate and acrylonitrile in the presence of catalytic amounts of 1,4‐diazabicyclo[2.2.2]octane to give the α‐hydroxyethylated products in good yields. No structure proof was given. The assignment eventually was shown to be correct, but since the initial disclosure was not followed by a journal publication, this remarkably simple, atom‐efficient, and useful reaction was ignored for a number of years, and it has been only fairly recently that its potential has begun to be explored. The transformation is now commonly referred to as the Baylis–Hillman reaction. This is unfortunate because credit for its invention clearly belongs to Morita, who five years earlier, in patents and a brief paper reported the same reaction with the exception that tertiary phosphines were used as the catalysts; he also proposed the currently accepted mechanism. Baylis and Hillman made reference to Morita's work in their patent application. It is true that tertiary amines in general are cheaper, less toxic, and more readily removed than tertiary phosphines. However, the latter sometimes give higher yields in shorter reaction times, and there are a number of examples where they are the only useful catalysts.The DABCO‐catalyzed reaction is slow, and reaction times at room temperature of days or even weeks are common. Attempts to remedy this situation by use of other amine catalysts, change of reaction temperature, high pressure, or microwave irradiation have been partially successful. Activated olefins other than acrylonitrile and acrylic esters that have now been shown to undergo the reaction include α,β‐unsaturated aldehydes and ketones, vinyl sulfoxides, vinyl sulfones, vinylsulfonates, and vinylphosphonates. β‐Substituted activated olefins do not normally react. Among electrophiles other than aldehydes, unactivated ketones undergo the Morita–Baylis–Hillman reaction only under high pressure, but activation such as in α‐halo ketones, α‐keto esters, α‐keto lactones, and nonenolizable α‐diketones often produces very reactive substrates. Imines also can be employed, provided they carry a sufficiently electronegative group on nitrogen.This chapter coverscatalyzedα‐hydroxyalkylations and α‐aminoalkylations of activated olefins. Transition metal catalyzed reactions of this type, are also included even though they proceed by a different mechanism. Transformations that require stoichiometric amounts of reagents or more than one step are summarized in the section on Comparison With Other Methods but are not included in the Tabular Survey. The Morita–Baylis–Hillman reaction has been reviewed before.
The Retro–Diels–Alder Reaction PartII. Dienophiles with One or More Heteroatom
Authors: Rickborn Bruce 
Published: April 2004

AbstractThis review (Part II) is topically organized around the dienophile that is generated in a retro [4 + 2] reaction, and to the extent possible follows the principles adopted for Part I, which covers reactions in which both dienophile bonding centers are carbon atoms. The present chapter encompasses retro–Diels–Alder (rDA) reactions in which one or both of the dienophile reaction centers are heteroatoms.Any of the other atoms in the starting material (cycloadduct) may be carbon or heteroatom. Substituents on all positions are encompassed, and any bond order available to any oxidation state of an element is included, as is bonding to non‐nearest neighbor atoms (e.g., bicyclics).The reader is directed to Part I (Vol. 52) for general discussion of the rDA reaction, the features that affect rates and outcome, and the use of acids, bases, other catalysts, and scavengers. Certain subclassifications (e.g., processes proposed under MS conditions, polymer applications) of rDA reactions have been omitted from both sections; these topics are listed in the Introduction to Part I. Citations to over 100 reviews on various aspects of the rDA reaction are collected at the beginning of the References to Part I. Those that are especially pertinent to Part II will be repeated here, in the context of the particular dienophile under discussion.The decision to split the review of the rDA reaction into two parts was based on the volume of literature encountered, as outlined in the Introduction to Part I. Active literature searching was concluded for both Parts in April 1995, although occasional more recent references have been included.
Preparation and Applications of Functionalized Organozinc Compounds
Authors: Knochel Paul , Millot Nicolas , Rodriguez Alain L. , Tucker Charles E. 
Published: April 2004

AbstractOrganozinc compounds have been known for more than 150 years. With the exception of zinc enolates (Reformatsky reagents) and iodomethylzinc derivatives (Simmons‐Smith, Furukawa, and Sawada reagents), their synthetic potential has only been recently recognized. This is certainly due to their low reactivity and to the absence of general methods of preparation. Although the carbon‐zinc bond in diethylzinc has a dissociation energy of 34.5 kcal/mol, it has, because of the similar electronegativities of zinc and carbon, a highly covalent character (ca. 85 %), which is comparable to a carbon‐tin bond. The carbon‐zinc bond is therefore inert to moderately polar electrophiles such as aldehydes, ketones, esters, or nitriles. On the other hand, the presence of empty low‐lyingporbitals at the zinc center allows transmetallations with a number of transition metal complexes. This is favored for both kinetic and thermo‐dynamic reasons. The availability ofdorbitals at the metal center in these compounds allows for new reaction pathways with electrophilic reagents that were not available for the corresponding zinc reagents. This reactivity has been exploited for the formation of new carbon‐carbon bonds and efficient cross‐coupling reactions between organozinc derivatives and unsaturated organic halides, as Negishi has demonstrated using catalytic amounts of palladium(0) salts. Similar catalytic processes have been reported with copper(I) and titanium(IV) complexes, which can mediate numerous reactions of organozinc reagents with organic electrophiles.The scope and synthetic applications of zinc organometallics were greatly extended when it was found that these species can accommodate a wide range of functional groups. They are ideally suited for the construction of polyfunctional organic molecules without the use of multiple protection and deprotection steps. Although some functionalized organozinc compounds bearing ester groups such had been reported, it was only recently that systematic studies have shown the synthetic potential of these reagents. This chapter describes methods for the preparation of functionalized organozinc halides, diorganozincs, and organozincates and their reactions with electrophilic reagents in the presence of transition metal catalysts, as well as synthetic applications demonstrating their synthetic utility for natural product synthesis. Only the preparation and reactivity of zinc organometallics bearing relatively reactive functional groups are covered. Thus, the chemistry of organozinc compounds bearing an ether, acetal, ketal, trialkylsilyl, or polyfluoroalkyl group is, in general, not covered.
The IntramolecularHeck Reaction
Authors: Link J. T. 
Published: April 2004

AbstractSince the discovery of the Heck reaction, the process has gained widespread acceptance within the synthetic community both as a practical tool and a research area. The intramolecular Heck reaction has enjoyed a similar renaissance, particularly within the last decade. The reaction has emerged as a reliable method for efficiently constructing small, medium, and large rings. Since the reaction occurs under mild and nearly neutral conditions, the functional group tolerance is high. Tandem reactions, which are initiated by intramolecular Heck reactions, have been developed allowing for multiple ring formations, cyclization and intermolecular coupling, and a multitude of other ever‐expanding possibilities. Furthermore, congested tertiary and quaternary centers can be efficiently constructed diastereoselectively or enantioselectively during the ring‐forming reaction. The numerous advances in reaction technology and capability have led to frequent application of the reaction in complex molecule synthesis and combinatorial library preparation. For the purposes of this chapter, the intramolecular Heck reaction is defined as the palladium[0]‐catalyzed intramolecular coupling of an aryl or alkenyl halide or perfluorosulfonate with an alkene, alkyne, allene, or arene.The mechanism of the Heck reaction is an active area of research. Precise mechanistic details vary substantially depending upon catalyst, substrate, additives, and reaction conditions. The introduction given here is designed to give the chemist a basic understanding of the currently accepted mechanisms to aid in the rational selection and optimization of reaction conditions. Application to total synthesis of natural products and intramolecular Heck reactions on polymer supports are discussed.
The α‐Hydroxy Ketone (α‐Ketol) and Related Rearrangements†
Authors: Paquette Leo A. , Hofferberth John E. 
Published: April 2004

Abstract
Treatment of suitable alpha‐hydroxy aldehydes and ketones with a base, a Bronsted or Lewis acid, or simply with heat has long been know to induce the 1,2‐shift of an alkyl or aryl substituent to form an isomeric product. The synthetic utility of the process was considerably expanded when applied to steroidal D‐ring homoannulations, and has more recently encompassed novel ring expansion to numerous complex target ring systems. The classical alpha‐ketol rearrangement shares, in common with other base‐promoted ketogenic isomerizations, the property of advancing from an alkoxide to a carbonyl group as the migrating center relocates its bonding electrons to the adjacent trigonal center. A distinctive feature of the title reaction, however, is its reversibility, such that the more stable alpha‐hydroxy carbonyl isomer is favored. The process has sometimes been termed the acyloin rearrangement.
This chapter focuses on the isomerization of alpha‐hydroxy ketones, aldehydes, and imines under various reaction conditions exclusive of photochemical activation. The literature coverage extends to 2000.
Since many of the steroidal transformations were carried out in early days when products were not always adequately characterized; errors in structural assignment were occasionally made. Experimental detail was sometimes lacking. To alleviate this problem, we have included only experiments that lead to reasonably pure products of established structure.
Geometry of adaptive control: optimization and geodesics
Authors: Colon Diego , Pait Felipe M. 
Published: April 2004

AbstractTwo incompatible topologies appear in the study of adaptive systems: the graph topology in control design, and the coefficient topology in system identification. Their incompatibility is manifest in the stabilization problem of adaptive control. We argue that this problem can be approached by changing the geometry of the sets of control systems under consideration: estimating np parameters in an np‐dimensional manifold whose points all correspond to stabilizable systems. One way to construct the manifold is using the properties of the algebraic Riccati equation. Parameter estimation can be approached as an optimal control problem akin to the deterministic Kalman filter, leading to algorithms that can be used in conjunction with standard observers and controllers to construct stable adaptive systems. Copyright © 2004 John Wiley & Sons, Ltd.
Convergence theory for multi‐input discrete‐time iterative learning control with Coulomb friction, continuous outputs, and input bounds
Authors: J. Driessen Brian , Sadegh Nader 
Published: April 2004

AbstractIn this paper we consider the problem of discrete‐time iterative learning control (ILC) for position trajectory tracking of multiple‐input, multiple‐output systems with Coulomb friction, bounds on the inputs, and equal static and sliding coefficients of friction. We present an ILC controller and a proof of convergence to zero tracking error, provided the associated learning gain matrices are scalar‐scaled with a sufficiently small positive scalar. We also show that non‐diagonal learning gain matrices satisfying the same prescribed conditions do not lead to the same convergence property. To the best of our knowledge, for problems with Coulomb friction, this paper represents a first convergence theory for the discrete‐time ILC problem with multiple‐bounded‐inputs and multiple‐outputs; previous work presented theory only for the single‐input, single‐output problem. Copyright © 2004 John Wiley & Sons, Ltd.
Development of an amperometric biosensor based on a redox‐mediator‐doped polypyrrole film
Authors: Rajesh  , Pandey Shyam S. , Takashima W. , Kaneto K. 
Published: April 2004

AbstractAn amperometric biosensor was developed for the quantitative estimation of phenolic compounds in aqueous media. The enzyme tyrosinase [poly(phenol oxidase) (PPO)] was adsorbed onto a hexacyanoferrate(II)‐ion‐doped conducting polypyrrole (PPY) film deposited on an indium tin oxide (ITO) coated glass‐plate support. The PPO activity in the PPO/Fe2+‐PPY/ITO film was assayed as a function of the concentration of phenolic compounds. Cyclic voltammetric studies were carried out on this enzyme electrode, and the surface morphology of the enzyme‐immobilized polymer film was studied with scanning electron microscopy. The results of the amperometric response of the PPO/Fe2+‐PPY/ITO film showed sensitivities of 0.14, 0.21, and 0.36 A M−1cm−2 and linear response ranges of 9.9–84.7, 6.7–72.6, and 3.9–48.8 μM for phenol, catechol, and p‐chlorophenol, respectively. The PPO/Fe2+‐PPY/ITO electrode exhibited a response time of about 50 s and was stable for about 12 weeks at 4°C. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 927–933, 2004
Ethoxylated polyethylenimine gel‐coated on textile‐grade acrylic fiber. A thermally regenerable superfast sorbent for water desalination
Authors: Chanda Manas , Sarkar Amitava , Modak Jayant M. 
Published: April 2004

AbstractA commercial acrylic fiber containing 92 wt % acrylonitrile was hydrolyzed to convert a part of its nitrile (CN) groups to carboxylic acid (COOH) groups and then was coated chemically with 80% ethoxylated polyethylenimine (EPEI) resin, followed by crosslinking with glutaraldehyde. The resulting sorbent, PAN(CO2H)(EPEI.XG), containing carboxylic acid groups and weakly basic tertiary amine groups in close proximity on the same fiber is found to simulate the well‐known Sirotherm™ resins used for partial desalination of brine solution by adsorbing the salt at ambient temperature and desorbing it at an elevated temperature in the same solution. The sorption behavior of the new sorbent was evaluated for solutes NaCl and MgCl2, showing saturation capacities of 0.797 and 0.877 meq/g (dry) sorbent fiber, respectively, at 30°C. The equilibrium sorption data show good agreement with both Langmuir and Freundlich isotherms for sorption from single‐component solutions and with Butler–Ockrent and LeVan–Vermeulen models for bicomponent sorption. Although the equilibrium uptake of NaCl reaches maximum in neutral solutions (pH ∼ 6.5), falling at both lower and higher pH, that of MgCl2 is augmented in alkaline pH due to additional sorption by cation exchange at the ionic sites formed at higher pH. The initial uptake of the salt, which is nearly instantaneous, exceeds the sorption value attainable at equilibrium. The high initial rate of salt uptake fits a shell‐core kinetic model for sorption on fiber of cylindrical geometry. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 883–893, 2004
Changes in properties of silane–water crosslinked metallocene ethylene‐octene copolymer after prolonged crosslinking time
Authors: Sirisinha Kalyanee , Meksawat Darinya 
Published: April 2004

AbstractThe silane–water crosslinking of metallocene ethylene–octene copolymer is described. Particular consideration is made on the changes in mechanical, thermal, and rheological properties of crosslinked polymers after prolonged crosslinking time. The silane grafting is carried out in a twin‐screw extruder, using a free‐radical reaction of vinyl trimethoxysilane and dicumyl peroxide. The crosslinking reaction is conducted at 70°C in the presence of water. The results show that the rate of gel formation is very high in the early stage of crosslinking process and decreases thereafter. The maximum gel content of 77% is obtained after 60 h of immersing time. Increasing the immersing time beyond 60 h, the gel content does not increase further. However, the FTIR results reveal an increase in siloxane linkages in those samples, indicating an increase in crosslink density without a simultaneous increase in gel content. This finding is supported by a rheological study where a significant increase in storage modulus is clearly observed. As a result of denser network, movement and flexibility of polymer chains are more restricted, leading to some changes in tensile properties. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 901–906, 2004
Polymer reaction in polycarbonate with Na2CO3
Authors: Takeda Kunihiko , Unno Haruo , Zhang Min 
Published: April 2004

AbstractThe recombination of polycarbonate (PC) chains has been researched as one of the studies on self‐repairing materials. The specimens, which included sodium carbonate and Tri(2,4‐di‐t‐buthylphenyl)phosphate, were treated at 120°C in a steam chamber and subsequently at 130°C under nitrogen atmosphere. The molecular weight of the specimen with 0.1 ppm of sodium carbonate increased during the subsequent treatment. The same tendency was observed when sodium carbonate was supplementally added to the specimen. In particular, the molecular weight little changed under severe condition when the concentration of sodium carbonate was controlled to be 100 to 1000 ppm. The result showed PC could be used as a self‐repairing material. The deterioration is expected to be minimized if the recovery rate is the same as the deterioration rate by applying these self‐repairing systems. The tensile strength, the transparency, and the reaction schemes are discussed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 920–926, 2004
Interchain crosslinkable polymer blends of polyurethane and polyacrylic elastomer (sulfur cure)
Authors: Khatua B.B. , Das C.K. 
Published: April 2004

AbstractBlends of polyurethane and polyacrylic elastomers prepared by three different blending techniques have been studied in different blend ratios. The processability of the polyurethane elastomer was improved as a result of blending with the polyacrylic elastomer. The blending technique has a significant role in determining the physical properties of the blends. Improvement of physical properties was observed in the blends containing the interchain crosslink bonds. IR spectral analysis suggested the formation of interchain crosslink between the two elastomers phases on heat treatment, before the addition of any curatives. Thermal stability of the blends was also improved when preblending and preheating techniques were applied. The extraction of the single phase by solvent was also restricted to a significant extent for the preheated sample probably due to the interchain crosslinking. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 845–853, 2004
Perfusion cultures of human tumor cells: a scalable production platform for oncolytic adenoviral vectors
Authors: Yuk Inn H. Y. , Olsen Matthew M. , Geyer Scott , Forestell Sean P. 
Published: April 2004

AbstractThis study demonstrates the novel use of the HeLaS3 human tumor cell line for propagating ONYX‐411, a recombinant oncolytic adenoviral vector. HeLaS3 cells enabled high levels of vector production without the risk of generating vector recombinants, which is possible with HEK293 cells. The development of a high‐cell‐density perfusion process using ATF technology yielded production levels as high as 6 × 1011 vp/mL, which was approximately sevenfold greater than the titers achieved in fed‐batch bioreactors. Several experiments were performed at the bench (15 L) and pilot (70 L) scales to demonstrate the robust and scalable nature of this industrially relevant technology. © 2004 Wiley Periodicals, Inc.
CFD studio: An educational software package for CFD analysis and design
Authors: Pieritz Romeu André , Mendes Rafael , da Silva Rodrigo F. A. F. , Maliska Clovis R. 
Published: April 2004

AbstractThis paper presents the general characteristics of the educational user‐friendly “CFD Studio” package designed for teaching fluid mechanics and heat transfer process, including conduction, coupled conduction/convection, natural and forced convection, external and internal flows. Therefore, general aspects of the three main modules—pre‐processor, solver, and post‐processor—are discussed aiming to show the generality of the tool. These modules are integrated in the application by a so‐called “numerical problem project” to guide the student through the steps to obtain the solution. © 2004 Wiley Periodicals, Inc. Comput Appl Eng Educ 12: 20–30, 2004; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.10055