Abstract Die K0enigs‐Knorr‐Kondensation (Helferich‐Modifikation) des α‐Glucosylpyranosylbromides (I) mit den anomeren galacto‐Nitrozuckern (IIa) bzw. (IIb) liefert die Disaccharide (IIIa) bzw. (IIIb); mit den gluco‐Nitrozuckern (IVa) bzw. (IVb) werden jeweils Gemische der α‐ (vorherrschender Anteil) und β‐glykosidisch verknüpften Disaccharide erhalten: a) Das Produktgemisch (Va) ist schwertrennbar; b) im Falle der Reaktion von (I) mit (IVb) kann nur das α‐verknüpfte Produkt (Vb) isoliert werden.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTBromination and lithiation: two important steps in the functionalization of polystyrene resinsM. Jean Farrall and Jean M. J. FrechetCite this: J. Org. Chem. 1976, 41, 24, 3877–3882Publication Date (Print):November 1, 1976Publication History Published online1 May 2002Published inissue 1 November 1976https://pubs.acs.org/doi/10.1021/jo00886a023https://doi.org/10.1021/jo00886a023research-articleACS PublicationsRequest reuse permissionsArticle Views2604Altmetric-Citations324LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

Abstract Novel approaches to macroporous polymeric separation media with enhanced pore size distributions, controlled surface chemistries, and excellent separation properties have been explored. In the first of these approaches, size‐monodisperse spherical polymeric particles containing both large and small pores are prepared with the use of a variety of polymeric porogens. The choice of polymeric porogen as well as its concentration greatly affects the pore size and pore size distribution of the final beads. The polymer beads obtained by this technique have been tested in size exclusion chromatography and in the separation of proteins in reversed‐phase mode. Techniques that allow the specific functionalization of pores according to their sizes have been developed. Thus, the surfaces of the large pores of the monodisperse particles can be made hydrophilic or chiral while the smaller pores remain hydrophobic or achiral. Similarly, a novel polymeric separation medium based on a continuous polymer rod incorporating macropores has been prepared by an in situ polymerization within the confines of the tube of a chromatographic column. For example, non‐particulate continuous polymer rods with flow‐through pores as well as separation pores have been prepared from styrene and divinylbenzene and used in the very fast (30 s) separation of proteins by reversed‐phase chromatography. Alternatively, continuous rods prepared from glycidyl methacrylate and ethylene dimethacrylate can be transformed into materials that are suitable for ion exchange or other chromatographic modes. A characteristic of the continuous polymeric rod media is their permeability which allows the mobile phase to flow through the medium without causing a high back‐pressure. The continuous rod‐shaped media can also be modified in pore size‐selective fashion to introduce different chemistries in the large and the small pores. These new media are advantageous as they are extremely easy to prepare, durable, require no packing, and can be used for a variety of separations.

Polyethylene encased porous poly(chloromethylstyrene-co-divinylbenzene) disks have been prepared by polymerization in a cylindrical glass mold and cut to a disk format. Following attachment of a free radical azo initiator 4,4'-azobis(4-cyanovaleric acid) to available functionalities at the surface of the pores, the polymerization of 2-vinyl-4,4-dimethylazlactone was initiated from the surface. To avoid an undesirable increase in flow resistance and to improve the yield of grafting, divinylbenzene was added to the polymerization mixture in order to form a layer of swellable reactive polymer gel within the pores. The use of these disks as scavenging filters to remove various amines from solutions in flow-through operations was demonstrated by effective removal of amines in a very short period of time from their solutions in a variety of solvents, even including alcohols and water.

Abstract Polymere Boronsäuren (I), speziell auf Basis eines schwach vernetzten Polystyrols, das nach Bromierung über eine Behandlung mit Butyllithium und anschließend mit Tributylborat erhalten werden kann, werden zur Trennung von Glykol‐Gemischen eingesetzt, wobei ein Stereoisomeres mit der Boronsäure ein Cyclokondensat bildet, während das andere Isomere abgetrennt werden kann.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe first direct formation of a Grignard reagent on an insoluble polymerS. Itsuno, G. D. Darling, J. M. J. Frechet, and H. D. H. StoverCite this: J. Org. Chem. 1987, 52, 20, 4644–4645Publication Date (Print):October 1, 1987Publication History Published online1 May 2002Published inissue 1 October 1987https://pubs.acs.org/doi/10.1021/jo00229a052https://doi.org/10.1021/jo00229a052research-articleACS PublicationsRequest reuse permissionsArticle Views246Altmetric-Citations34LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

A new strategy for the preparation of functional, multiarm star polymers via nitroxide-mediated "living" radical polymerization has been explored. The generality of this approach to the synthesis of three-dimensional macromolecular architectures allows for the construction of nanoscopically defined materials from a wide range of different homo, block, and random copolymers combining both apolar and polar vinylic repeat units. Functional groups can also be included along the backbone or as peripheral/chain end groups, thereby modulating the reactivity and polarity of defined portions of the stars. This modular approach to the synthesis of three-dimensional macromolecules permits the application of these tailored materials as multifunctional hosts for hydrogen bonding, nanoparticle formation, and as scaffolds for catalytic groups. Examples of applications of the functional stars in catalysis include their use in a Heck-type coupling as well as an enantioselective addition reaction.

Several new functionalized chromophores have been prepared and tested in the preparation of optically stable, photopatternable, NLO polymers for second harmonic generation at the diode laser wavelength of 820 nm. In particular, chromophores containing the sulfonamide or sulfonate ester functionalities have been found to be extremely versatile as they allow attachment of a polymerizable group at the electron-poor end of NLO chromophores. The results of model studies confirm that the sulfonamide groups do not have a deleterious effect on NLO properties. Several new monomers containing 4-alkoxy-4'- sulfonamido-stilbene moieties have been prepared. The 4- alkoxy end of the chromophore 'is designed to allow its incorporation into a linear polymer backbone. The sulfonamido end of the chromophore has a polymerizable double bond that can be photocrosslinked after poling of the chromophores. As it is extremely important to carry out the photopatterning step without affecting the NLO chromophore or introducing any color into the imaged polymer, novel photoinitiators were tested and found to be suitable. The radiation induced photo-patterning step can be done without causing isomerization of the stilbene chromophores, or introducing any color into the patterned coating

Abstract Linear copolymers that have pendant coumarin‐2 and coumarin‐343 chromophores were prepared as analogues to previously synthesized light‐harvesting dendrimers. The chromophore ratios within these polymers were maintained similar to those of the various generation dendrimers to investigate the effect of polymer architecture on the energy‐transfer efficiency between the coumarin‐2 donors and coumarin‐343 acceptors. Both physical and photophysical properties of these polymers were analyzed and compared to those of the analogous dendrimers. Energy‐transfer efficiencies were relatively high in the polymers; however, deleterious excimer formation between the coumarin‐343 chromophores diminished the quantum yield of fluorescence of the polymers when compared to the analogous dendrimers. Overall, it was found that the ultimate performance of the dendritic light‐harvesting antennae was superior to that of the polymeric analogues, but the polymers were more practical in terms of synthetic accessibility. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1366–1373, 2001

Abstract Aus einem Styrol‐Divinylbenzol‐Copolymeren (I) entsteht mit Benzoylchlorid/A1uminiumchlorid das polymere Keton (II), das mit Phenylmagnesiumbromid über das Carbinol (IIIa) in das polymere Tritylchlorid (IIIb) übergeht.

A new approach to the controlled synthesis of multicomponent dendrimers is presented, in which three oligonucleotide-dendron conjugates were synthesized using solid phase techniques and hybridized to create a second generation polyester dendrimer with DNA as a core and bearing two types of peripheral functional groups.

Since the concept of chemical amplification in microlithography was first developed in the early 1980`s, a number of new resists based on acid catalyzed thermolysis have been developed. This report describes the first chemically amplified resist operating on the basis of photogenerated base. The concept is demonstrated with poly(2-cyano-2(p-vinylphenyl)butanoic acid) which decarboxylates readily under basic conditions. A resist system consisting of this polymer and an amine photogenerator, bis[((2,6-dinitrobenzyl)oxy)carbonyl]hexan-1,6-diamine, was formulated. The sensitivity of this resist is 1.4 mJ/cm{sup 2} with a contrast ({gamma}) of 13.7. This high sensitivity confirms that chemical amplification is achieved as the photogenerated base is not consumed in the overall decarboxylation process. The mechanistic insights of the decarboxylation reaction in a polymer matrix will also be discussed.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSolid-phase synthesis of oligosaccharides. II. Steric control by C-6 substituents in glucoside synthesesJean M. Frechet and Conrad SchuerchCite this: J. Am. Chem. Soc. 1972, 94, 2, 604–609Publication Date (Print):January 1, 1972Publication History Published online1 May 2002Published inissue 1 January 1972https://pubs.acs.org/doi/10.1021/ja00757a047https://doi.org/10.1021/ja00757a047research-articleACS PublicationsRequest reuse permissionsArticle Views410Altmetric-Citations98LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

The design of resists based on the principle of chemical amplification has provided imaging materials with remarkable sensitivity. These materials all function on the basis of photo-generation of a latent image of catalyst. In a subsequent step that is usually thermally activated, the catalyst acts on some part of the formulation to modify the solubility of the film. In most cases reported to date, the systems depend on acid that is generated by the irradiation of neutral compounds which produce acidic radiolysis products. Acid catalysis of side chain cleavage, cross-linking, and hydrolysis are but a few of the reactions that have been exploited in the design of acid catalyzed, chemically amplified resists. This paper now reports the authors` work on the use of photo-generated base in the design of resists that derive high sensitivity from base catalyzed chemical transformations. A variety of base catalyzed reactions have been auditioned for this application.