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91.
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93.
Shohei Ida Makoto Ouchi Mitsuo Sawamoto 《Journal of polymer science. Part A, Polymer chemistry》2010,48(6):1449-1455
We first achieved the living cationic polymerization of azide‐containing monomer, 2‐azidoethyl vinyl ether (AzVE), with SnCl4 as a catalyst (activator) in conjunction with the HCl adduct of a vinyl ether [H‐CH2CH(OR)‐Cl; R ? CH2CH2Cl, CH2CH(CH3)2]. Despite the potentially poisoning azide group, the produced polymers possessed controlled molecular weights and fairly narrow distributions (Mw/Mn ~ 1.2) and gave block polymers with 2‐chloroethyl vinyl ether. The pendent azide groups are easily converted into various functional groups via mild and selective reactions, such as the Staudinger reduction and copper‐catalyzed azide‐alkyne 1,3‐cycloaddition (CuAAC; a “click” reaction). These reactions led to quantitative pendent functionalization into primary amine (? NH2), hydroxy (? OH), and carboxyl (? COOH) groups, at room temperature and without any acidic or basic treatment. Thus, poly(AzVE) is a versatile precursor for a wide variety of functional vinyl ether polymers with well‐defined structures and molecular weights. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1449–1455, 2010 相似文献
94.
Shohei Izawa 《Algebra Universalis》2013,69(4):327-356
First, we prove two finite algebras are categorically equivalent if and only if the matrix products of their irredundant non-refinable covers are isomorphic. Second, we characterize families of irreducible algebras such that there exists an algebra whose neighbourhoods in an irredundant non-refinable cover are isomorphic to the respective irreducible algebra in the given family. Finally, we exhibit two facts by constructing examples. The first one is that there is a family of irreducible algebras such that there are many algebraic structures whose neighbourhoods in an irredundant non-refinable cover are isomorphic to the respective irreducible algebra in the given family. The second example is an algebra such that the matrix product of an irredundant non-refinable cover is bigger than the given algebra. 相似文献
95.
Taihei Nishiyama Yoshifumi Kusumoto Ken Okumura Kanako Hara Shohei Kusaba Keiko Hirata Yukihiro Kamiya Minoru Isobe Prof. Dr. Keiji Nakano Dr. Hiyoshizo Kotsuki Prof. Dr. Yoshiyasu Ichikawa Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(2):600-610
The first total synthesis of amino sugar antibiotic glycocinnasperimicin D ( 1 ) has been achieved by a convergent, three‐component coupling strategy. The key steps involve the Heck–Mizoroki reaction by using the iodophenyl glycoside 50 and acryl amide 32 to furnish the right core structure of 1 , and the construction of the urea glycoside employing the reaction of glycosyl isocyanate 8 with amino sugar 9 . Glycosyl isocyanate 8 was prepared by the oxidation of isonitrile 10 , which displayed excellent reactivity in the coupling event. Synthetic roadblocks, encountered during this synthetic effort, have led to the development of the α‐selective, Lewis acid catalyzed phenyl glycosylation process with 2‐amino‐hexopyranose and a procedure for acetonide deprotection without affecting the silyl ethers. 相似文献
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97.
meso-Heptakis(pentafluorophenyl) heptaphyrin(1.1.1.1.1.1.1) (1) was prepared by a stepwise route in 39 % yield and its unique N-fusion reaction (NFR) sequence has been revealed; this reaction leads to singly-, doubly-, and quadruply N-fused heptaphyrins (4, 5, and 6) in good yields. These transformations are facilitated by the inherent conformational distortion of 1 as well as the distorted, folded conformations of N-fused heptaphyrins 4 and 5. The proximate arrangement of the three pyrrole units in 6 allowed for the formation of the tripyrrolylboron(III) complexes 7, 8, and 9 with unique coordination features. Molecules 1, 5, and 9 were structurally characterized by X-ray crystallography. In addition, the boron complexes 7, 8, and 9 displayed weak but distinct fluorescence in the near infrared region. 相似文献
98.
The synthesis, reactivity, and bonding properties of several pentacoordinate P-phenyl-substituted 1H-phosphirenes are discussed. X-ray crystallographic analysis of one of them reveals a highly distorted square pyramidal (SP) arrangement around the phosphorus. NMR studies confirm that they retain the SP structure in solution and demonstrate that the endocyclic P-C bonds in the three-membered ring have a very high degree of p character, which results from their being both basal bonds in the SP structure and endocyclic bonds of the three-membered ring. Structural parameters of the three-membered ring of the pentacoordinate phosphirenes obtained by experiment and theoretical calculations are very close to those of a tetracoordinate phosphirenium cation. Thus, by analogy with tetracoordinate phosphirenium cations, it can be considered that a sigma-pi interaction between the sigma orbital of the apical bond and the pi orbital of the C=C bond in the three-membered ring is operative in pentacoordinate phosphirenes. The sigma-pi interaction is found to lower the reactivity of the C=C bond of the three-membered ring. The reactivities of the pentacoordinate phosphirenes are also affected by the substituent on the carbon atom in the three-membered ring. 相似文献
99.
[reaction: see text] The iron-catalyzed cross-coupling reaction of alkenyl sulfides with Grignard reagents is described. While the cross-coupling proceeds efficiently at alkenyl-S bonds, almost no cross-coupling takes place at aryl-S bonds, attesting to a unique selectivity of iron catalysis. The beneficial effect of potentially coordinating 2-pyrimidyl group on sulfur is also described. 相似文献
100.
Solid-state polycondensation of a natural saccharide was found to take place in the presence of H3PO4(5 mol%) at 110 degrees C under a N2 flow, giving a highly branched polysaccharide (conv. 11-84%, Mw = 1400-19000, Mn = 1200-3700); the reaction mixture was powdery throughout the polymerization. Interestingly, alpha- and beta-anomers showed different polymerization behaviour; the former was polymerized more slowly, however, they gave comparable molecular weight polymers. The polysaccharide product was per-O-methylated and subjected to structure analyses. The acid-hydrolysis products, the partially O-methylated monosaccharides, suggested that the polysaccharide products have highly branched structures. MALDI-TOF mass analysis revealed that intramolecular glycosylation and acetal exchange reactions are involved in the polymerization mechanism. 相似文献