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Dendritic Core (dendritic + core)
Selected AbstractsHomogeneous Stabilization of Pt Nanoparticles in Dendritic Core,Multishell Architectures: Application in Catalytic Hydrogenation Reactions and RecyclingCHEMCATCHEM, Issue 7 2010Juliane Keilitz Abstract Core,multishell architectures are a new approach to homogeneously stabilize metal nanoparticles for harsh conditions. Herein, we present the synthesis and stabilization of Pt nanoparticles in dendritic core,multishell polymers and their application in hydrogenation reactions. The successful recycling of the catalyst was demonstrated for the hydrogenation of methyl crotonate 1 and was either achieved by ultrafiltration or in a two-phase system for at least 14,cycles. Thereby, the total turnover number (TON) was increased to 22,000. In the recycling experiments, low metal leaching into the product (as low as 0.3,ppm) was detected. Additionally, the selective hydrogenation of isophorone 3 was investigated and selectivities of 99:1 for CC versus CO hydrogenation were achieved. [source] ChemInform Abstract: Convenient Synthesis of a Tetrathienyl Dendritic Core.CHEMINFORM, Issue 17 2009Raphael P. Jimenez Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Chiral Polyamino Alcohols via Hydroaminomethylation: A New Class of Polyamines for Dendritic Cores and Ligand PrecursorsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2009Muhammad Afzal Subhani Abstract In this contribution, the synthesis of a new class of chiral polyamino alcohols (PAA) via a two-step hydroaminomethylation/hydrolysis procedure is reported. The chiral polyamines are obtained by hydroaminomethylation of N -olefinic oxazolidinones with different amines in first step followed by hydrolysis of the resulting polyamines to give the chiral PAA in the second step. The dendritic chiral PAA (Mw=1300,1400,g,mol,1) are also synthesized efficiently through a multifold hydroaminomethylation/hydrolysis procedure. Furthermore, chiral PAA are investigated as ligands in ruthenium-catalyzed asymmetric hydrogen transfer reduction of acetophenone to 1-phenyl alcohol. [source] Dendrimers as scaffolds for multifunctional reversible addition,fragmentation chain transfer agents: Syntheses and polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2004Xiaojuan Hao Abstract The synthesis and characterization of novel first- and second-generation true dendritic reversible addition,fragmentation chain transfer (RAFT) agents carrying 6 or 12 pendant 3-benzylsulfanylthiocarbonylsulfanylpropionic acid RAFT end groups with Z-group architecture based on 1,1,1-hydroxyphenyl ethane and trimethylolpropane cores are described in detail. The multifunctional dendritic RAFT agents have been used to prepare star polymers of poly(butyl acrylate) (PBA) and polystyrene (PS) of narrow polydispersities (1.4 < polydispersity index < 1.1 for PBA and 1.5 < polydispersity index < 1.3 for PS) via bulk free-radical polymerization at 60 °C. The novel dendrimer-based multifunctional RAFT agents effect an efficient living polymerization process, as evidenced by the linear evolution of the number-average molecular weight (Mn) with the monomer,polymer conversion, yielding star polymers with molecular weights of up to Mn = 160,000 g mol,1 for PBA (based on a linear PBA calibration) and up to Mn = 70,000 g mol,1 for PS (based on a linear PS calibration). A structural change in the chemical nature of the dendritic core (i.e., 1,1,1-hydroxyphenyl ethane vs trimethylolpropane) has no influence on the observed molecular weight distributions. The star-shaped structure of the generated polymers has been confirmed through the cleavage of the pendant arms off the core of the star-shaped polymeric materials. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5877,5890, 2004 [source] Homogeneous Stabilization of Pt Nanoparticles in Dendritic Core,Multishell Architectures: Application in Catalytic Hydrogenation Reactions and RecyclingCHEMCATCHEM, Issue 7 2010Juliane Keilitz Abstract Core,multishell architectures are a new approach to homogeneously stabilize metal nanoparticles for harsh conditions. Herein, we present the synthesis and stabilization of Pt nanoparticles in dendritic core,multishell polymers and their application in hydrogenation reactions. The successful recycling of the catalyst was demonstrated for the hydrogenation of methyl crotonate 1 and was either achieved by ultrafiltration or in a two-phase system for at least 14,cycles. Thereby, the total turnover number (TON) was increased to 22,000. In the recycling experiments, low metal leaching into the product (as low as 0.3,ppm) was detected. Additionally, the selective hydrogenation of isophorone 3 was investigated and selectivities of 99:1 for CC versus CO hydrogenation were achieved. [source] New Polyalkynyl Dendrons and Dendrimers: "Click" Chemistry with Azidomethylferrocene and Specific Anion and Cation Electrochemical Sensing Properties of the 1,2,3-Triazole-Containing DendrimersCHEMISTRY - A EUROPEAN JOURNAL, Issue 12 2009Jérémy Camponovo Abstract Dendrimers for ion sensing: The synthesis and use of new tris-alkynyl dendrons are reported. So-called "click" reactions of the dendrimers described with azidomethylferrocene give 27-ferrocenyl, 81-ferrocenyl, and 243-ferrocenyl dendrimers. Electrochemical recognition of oxo-anions and Pd2+ cations has been compared using the three polyferrocenyl dendrimers. The synthesis and use of the new tris-alkynyl dendrons 2 to 5 are reported, including the Williamson reaction of 5 with 9-iodo (9), 27-iodo (11), and 81-iodo (12) dendritic cores to yield 27-alkynyl (13), 81-alkynyl (14), and 243-alkynyl (15) dendrimers. So-called "click" reactions of these three dendrimers with azidomethylferrocene (20) give 27-ferrocenyl (16), 81-ferrocenyl (17), and 243-ferrocenyl (18) dendrimers. Electrochemical recognition of oxo-anions (H2PO4, and ATP2,) and Pd2+ cation has been compared using the three polyferrocenyl dendrimers. Derivatization of Pt electrodes with the dendrimers for recognition becomes more facile with increasing size of the dendrimer. This first "click" dendrimer bearing 243-ferrocenyl groups is the best one in the series to obtain robust, recyclable modified Pt electrodes, whereas previous "click" ferrocenyl dendrimers have not been suitable for this purpose. Nous reportons ici la synthèse et l'utilisation de nouveaux dendrons tris-alcynes (composés 2 à 5). La réaction de Williamson entre 5 et les c,urs dendritiques polyiodés comportant 9, 27 ou 81 branches (composés 9, 11 et 12) conduit aux dendrimères poly-alcynes à 27, 81 et 243 branches respectivement (composés 13 à 15). La réaction "click" de ces dendrimères avec l'azidométhylferrocène (20) permet d'obtenir des dendrimères polyferrocéniques à 27, 81 et 243 branches (composés 16 à 18). La reconnaissance électrochimique d'oxo-anions (H2PO4,et ATP2,) et du cation Pd2+est comparée avec trois dendrimères polyferrocéniques, et l'obtention d'électrodes de Pt modifiées à l'aide de ces dendrimères pour cette reconnaissance est de plus en plus facile lorsque la taille du dendrimère augmente. Le premier dendrimère "click" comportant 243 ferrocènes est le meilleur de la série pour la modification d'électrodes de Pt. Ces électrodes sont robustes et recyclables avec ce dendrimère, alors que les dendrimères "click" précédemment publiés n'étaient pas utilisables pour cette fonction. [source] | ||||||||||