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Allyl Groups (allyl + groups)
Selected AbstractsCatalytic Conjugate Addition of Allyl Groups to Styryl-Activated Enones.CHEMINFORM, Issue 25 2007Joshua D. Sieber 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, please click on HTML or PDF. [source] Synthesis of a Fusion-Isomeric Cellobionoimidazole and Its Evaluation against the syn -Protonating Glycosidase Cel7AHELVETICA CHIMICA ACTA, Issue 12 2005Narinder Mohal The fusion-isomeric cellobinoimidazole 2, a potential inhibitor of the syn -protonating , -glycosidase Cel7A, was synthesised by Koenigs,Knorr glycosylation of the ,- D -arabinopyranoside 32, followed by selective hydrolysis. Glycosylation of 32 with acetobromoglucose 6 proceeded with poor diastereoselectivity, giving the desired 1,3-linked , - d- disaccharide 35 as minor product, besides the major 1,3-linked ,- d- disaccharide 36. Hg2+ -Promoted glycosylation of 32 led predominantly to the 1,2-ortho ester 33. Sequential removal of the silyl, acetyl, and allyl groups of 35 led to a 45,:,55 equilibrium mixture 2 and the manno -configured isomer 39. Similarly, deprotection of 36 gave a mixture of the maltonoimidazole 42 and the manno -configured isomer 43. According to a known protocol, the glycosyl acceptor 32 was synthesised in eleven steps and an overall yield of 8,13% from D -lyxose. The silylated arabinopyranosyl moiety of the ,- d- glucosides 13,19, 33, 34, and 36 adopts a 4C1 conformation, while the arabinopyranosyl moiety of the , - d- glucosides 17 and 35 exists as a 1,:,3,mixture of 4C1 and 1C4 conformers, as a result of the combined preferred axial orientation of bulky vicinal substituents and the anomeric effect. MM3* Modelling evidences a preferred 4C1 conformation of 35 and 36, and stronger steric interactions between the pyranosyl moieties of 35. The equilibrium mixture 2/39 proved a poor inhibitor of Cel7A with an IC50 value of ca. 4,mM. [source] Comparative studies on the pyrolysis of N -arylideneaminoamides: Kinetic and mechanistic studiesINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 2 2007Nouria A. Al-Awadi Rates of thermal decomposition of title compounds have been measured using a static reaction system. They undergo a unimolecular first-order elimination to give arylnitrile and the corresponding substituted amides. The decomposition parallels that of N -arylidenamino cyclic amide. The relative elimination rates at 600 K were calculated. The kinetic data reveal that the electronic effects of substituents, such as methyl, phenyl, benzyl, and allyl groups, are associated with the opposing directions in which the lone pair of electrons on the nitrogen atom of the arylidene moiety is being delocalized. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 39: 59,66, 2007 [source] Synthesis and characterization of a cured epoxy resin with a benzoxazine monomer containing allyl groupsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Shiao-Wei Kuo Abstract Vinyl-terminated benzoxazine (VB-a), which can be polymerized through ring-opening polymerization, was synthesized through the Mannich condensation of bisphenol A, formaldehyde, and allylamine. This VB-a monomer was then blended with epoxy resin and then concurrently thermally cured to form an epoxy/VB-a copolymer network. To understand the curing kinetics of this epoxy/VB-a copolymer, dynamic differential scanning calorimetry measurements were performed by the Kissinger and Flynn,Wall,Ozawa methods. Fourier transform infrared (FTIR) analyses revealed the presence of thermal curing reactions and hydrogen-bonding interactions of the epoxy/VB-a copolymers. Meanwhile, a significant enhancement of the ring-opening and allyl polymerizations of the epoxy was observed. For these interpenetrating polymer networks, dynamic mechanical analysis and thermogravimetric analysis results indicate that the thermal properties increased with increasing VB-a content in the epoxy/VB-a copolymers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Anionic alternating copolymerization of 3,4-dihydrocoumarin and glycidyl ethers: A new approach to polyester synthesisJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2008Kazuya Uenishi Abstract Anionic copolymerizations of 3,4-dihydrocoumarin (DHCM) and a series of glycidyl ethers (n -butyl glycidyl ether, tert -butyl glycidyl ether, and allyl glycidyl ether) with 2-ethyl-4-methylimidazole as an initiator proceeded in a 1:1 alternating manner to give the corresponding polyesters, whose structures were confirmed by spectroscopic analyses and reductive scission of the ester bonds in the main chain with lithium aluminum hydride, followed by detailed analyses of the resulting fragments. The polyester obtained by the copolymerization of DHCM and allyl glycidyl ether inherited the allyl groups in the side chain, whose applicability to chemical modifications of the polyester was successfully demonstrated by a platinum-catalyzed hydrosilylation reaction. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4092,4102, 2008 [source] Temperature-sensitive hydrogel microspheres formed by liquid,liquid phase transitions of aqueous solutions of poly(N,N -dimethylacrylamide- co -allyl methacrylate)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2005Xiangchun Yin Abstract Poly(N,N -dimethylacrylamide- co -allyl methacrylate) (DMA- co -AMA) copolymers were prepared by the copolymerization of N,N -dimethylacrylamide with allyl methacrylate (AMA). The methacryloyl group of AMA reacted preferentially, and this resulted in pendant allyl groups along the copolymer chains. Aqueous solutions of these DMA- co -AMA copolymers were thermoresponsive and showed liquid,liquid phase transitions at temperatures that depended on the AMA content. Hydrogel microspheres were prepared from these thermally phase-separated liquid microdroplets by the free-radical crosslinking of the pendant allyl groups. The morphologies of the resulting thermoresponsive microspheres as a function of the reaction temperature and the amount of the initiator were examined. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1641,1648, 2005 [source] Micron-granula polyolefin with self-immobilized nickel and iron diimine catalysts bearing one or two allyl groupsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2004Guoxin Jin Abstract Self-immobilized nickel and iron diimine catalysts bearing one or two allyl groups of [ArNC]2(C10H6)NiBr2 [Ar = 4-allyl-2,6-(i -Pr)2C6H2] (1), [ArNC(Me)][Ar,N C(Me)]C5H3NFeCl2 [Ar = Ar, = 4-allyl-2,6-(i -Pr)2C6H3, Ar = 2,6-(i -Pr)2C6H3, and Ar, = 4-allyl-2,6-(i -Pr)2C6H3] were synthesized and characterized. All three catalysts were investigated for olefin polymerization. As a result, these catalysts not only showed high activities as the catalyst free from the allyl group, such as [ArNC]2C10H6NiBr2 (Ar = 2,6-(i-Pr)2C6H2)], but also greatly improved the morphology of polymer particles to afford micron-granula polyolefin. The self-immobilization of catalysts, the formation mechanism of microspherical polymer, and the influence on the size of the particles are discussed. The molecular structure of self-immobilized nickel catalyst 1 was also characterized by crystallographic analysis. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1018,1024, 2004 [source] A Defect-Free Ring Polymer: Size-Controlled Cyclic Poly(tetrahydrofuran) Consisting Exclusively of the Monomer Unit,MACROMOLECULAR RAPID COMMUNICATIONS, Issue 14 2008Yasuyuki Tezuka Abstract A series of size-controlled, cyclic poly(tetrahydrofuran)s ( of 4,400,8,600) that consist exclusively of the monomer, i.e., oxytetramethylene, unit (I) have been prepared in high yield through the metathesis polymer cyclization of a telechelic precursor having allyl groups, 1, in the presence of a Grubbs catalyst, and the subsequent hydrogenation of the linking, i.e., 2-butenoxy, unit in the presence of an Adams' catalyst (PtO2). A remarkable topology effect has subsequently been observed upon the isothermal crystallization of these two model polymers, showing distinctive spherulite growth rates and spherulite morphologies in comparison with the relevant linear poly(tetrahydrofuran) counterpart that has ethoxy end groups (II). [source] Topologically Chiral Covalent Assemblies of Molecular Knots with Linear, Branched, and Cyclic ArchitecturesCHEMISTRY - A EUROPEAN JOURNAL, Issue 11 2004Oleg Lukin Dr. Abstract Selectively functionalized molecular knots (knotanes) of the amide-type have been used as building blocks in syntheses of higher covalent assemblies composed of up to four knotane units. Preparation of linear and branched tetraknotanes consisted of the consecutive selective removal of allyl groups followed by linking of the intermediate hydroxyknotanes with biphenyl-4,4,-disulfonyl chloride. Macrocyclic knotane oligomers involving two, three, and four knotane moieties were obtained by high-dilution cyclization of dihydroxyknotane and biphenyl-4,4,-disulfonyl chloride. Due to their relation with cyclophanes, the latter class of oligomeric knotanes was termed "knotanophanes". Chiral resolution analysis of new oligoknotanes has been attempted on chemically bonded Chiralpak AD stationary phases, however met severe difficulties due to their complex isomeric compositions, and in most cases a significant overlap of the isomer fractions was observed. In spite of the limits of presently available chiral stationary phases that allowed only partial resolution of the synthesized topologies, oligoknotanes have been shown to be of high fundamental interest due to their unprecedented chirality. The chirality descriptions of topologically chiral unsymmetrical dumbbell 4, and the linear tetraknotane 5 are analogous to the Fischer projections of erythrose/threose and hexaric acid, respectively, while the isomeric composition of the branched tetraknotane 8 is completely unique. Moreover, the linear and branched tetraknotanes are constitutional isomers. Chirality of knotanophanes represents, in turn, analogies to known cyclic forms of peptides or sugars with multiple stereogenic centers. [source] Dumbbell-shaped Carbosilane Dendrimers Based on 1,6-HexanediolCHINESE JOURNAL OF CHEMISTRY, Issue 1 2005Xin-De Tang Abstract Novel carbosilane dendrimers based on 1,6-hexanediol were prepared by divergent approach. Using 1,6-hexanediol-based diallyl ether as the core molecule, the dendrimers were prepared to the third generation with 54 allyl groups on the periphery by alternate hydrosilylation-allylation reactions. [source] | |||||||||||||