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Michael Seitz 《Tetrahedron》2006,62(42):9973-9980
Highly modular N,Y,Z,Y,N-ligands (Y=N, O, S; Z=N, NO, OH, OMe) have been prepared using bis(oxazoline) building blocks either as nucleophiles or as electrophiles in coupling reactions with central aromatic units. This way, a great variety of pentadentate bis(oxazoline) ligands in diastereo- and enantiomerically pure form become readily available, which are useful for the construction of helical metal complexes with predetermined chirality. 相似文献
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Poly(2‐oxazoline) hydrogels crosslinked with aliphatic bis(2‐oxazoline)s: Properties,cytotoxicity, and cell cultivation
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Anna Zahoranová Zuzana Kroneková Miroslav Zahoran Dušan Chorvát Jr. Ivica Janigová Juraj Kronek 《Journal of polymer science. Part A, Polymer chemistry》2016,54(11):1548-1559
A series of hydrogels from 2‐ethyl‐2‐oxazoline and three bis(2‐oxazoline) crosslinkers—1,4‐butylene‐2,2′‐bis(2‐oxazoline), 1,6‐hexamethylene‐2,2′‐bis(2‐oxazoline), and 1,8‐octamethylene‐2,2′‐bis(2‐oxazoline)—are prepared. The hydrogels differ by the length of aliphatic chain of crosslinker and by the percentage of crosslinker (2–10%). The influence of the type and the percentage of the crosslinker on swelling properties, mechanical properties, and state of water is studied. The equilibrium swelling degree in water ranges from 2 to 20. With a proper selection of the crosslinker, Young's modulus can be varied from 10 kPa to almost 100 kPa. To evaluate the potential for medical applications, the cytotoxicity of extracts and the contact toxicity toward murine fibroblasts are measured. The hydrogels with the crosslinker containing a shorter aliphatic exhibit low toxicity toward fibroblast cells. Moreover, the viability and the proliferation of pancreatic β‐cells incubated inside hydrogels for 12 days are analyzed. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1548–1559 相似文献
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Robert Luxenhofer Stephan Huber Julia Hytry Jing Tong Alexander V. Kabanov Rainer Jordan 《Journal of polymer science. Part A, Polymer chemistry》2013,51(3):732-738
We describe the synthesis and characterization of the first water‐soluble and chiral poly(2,4‐disubstituted‐2‐oxazoline)s. While poly(2,4‐dimethyl‐2‐oxazoline)s are water soluble up to 100 °C, aqueous solutions of poly(2‐ethyl‐4‐methly‐2‐oxazoline) exhibit a lower critical solution temperature. This is discussed in context with its constitutional isomers poly(2‐oxazoline)s and poly(2‐oxazine)s. Circular dichroism spectroscopy revealed strong Cotton effects, which are also responsive to temperature in aqueous solution. It is therefore hypothesized that structures, comparable to polyproline helices, are formed in aqueous solution. In contrast to polyproline, poly(2,4‐disubstituted‐2‐oxazoline)s are highly water soluble and therefore represent very interesting pseudo‐polypeptides that may be useful to develop responsive biomimetic biomaterials. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
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BinFU DaMingDU QingXIA 《中国化学快报》2004,15(4):383-385
The synthesis of bis(oxazoline) dicarboxylate derivatives was investigated.Diethyl-aminosulfur trifluoride (DAST) was used as a convenient cyclization reagent in the synthesis of bis(oxazoline) dicarboxylate derivatives,which can not be obtained by the general method using MsC1 and Et3N as dehydrating cyclization reagent. 相似文献
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《Tetrahedron: Asymmetry》2001,12(10):1475-1478
A chiral bis(oxazoline) was grafted on ArgoGel and used in the palladium-catalysed substitution of (±)-1,3-diphenyl-2-propenyl acetate with dimethyl malonate. The enantioselectivity was the same as that observed when the analogous monomeric catalyst was used (94–95% e.e.), despite the fact that the C2 symmetry of the ligand was affected when coupled to the polymer. The polymer-supported catalyst could be recycled several times after removal of precipitated Pd(0). The polymer-bound bis(oxazoline) was also applied in a zinc-catalysed Diels–Alder reaction but lower selectivity and reactivity than the monomer was observed. 相似文献
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改进了邻溴苯基-2-(口恶)唑啉的合成方法,使得N-(β-羟乙基)-2-(口恶)溴苯甲酰胺在氯化亚砜作用下缩合成唑啉的收率从40%左右提高到84%,并避免了使用NaH试剂,为芳基-2-(口恶)唑啉的合成提供一条方便、经济的路线.实验结果表明,反应温度对唑啉的收率的影响显著,随着反应温度的升高收率明显降低,室温下几乎得不到目标产物.根据实验结果推测其反应过程是经过互变异构酰亚胺中间物Ⅰ进行的. 相似文献
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Tris(imidazolines) are assembled via triple hydrogen bonding interactions to give rise to a stacked polymeric structure. A mixture of chiral tris(oxazoline) and achiral tris(imidazoline) generates a helical assembly in which the helical direction of the assembly is unidirectionally induced by the chirality of tris(oxazoline). 相似文献
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Enantioselective recognition of amino acids has been studied with C2-symmetric chiral pyridine bis(oxazoline)-copper(II) complexes at physiological pH condition. UV-visible titration revealed strong binding of submillimolar dissociation constant between pyridine bis(oxazoline)-copper(II) complex and amino acids in aqueous solution. Moderate selectivity of up to 2:1 between d- and l-amino acids was achieved. The enantiomers were baseline resolved by capillary electrophoresis, using the bis(l-lysine)-copper(II) complex as a chiral selector. 相似文献
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A straightforward synthesis of chiral aza-bis(oxazoline) (Azabox) ligands from commercially available amino alcohols is described. The new protocol allows access to previously reported Azabox ligands in considerably improved yields but also to new derivatives, including non-C2-symmetrical ones. 相似文献
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Abstract The monomer 2-(4-aminophenyl)oxazoline has been prepared in good yield and briefly investigated for cationic, homopolymerization and copolymerization characteristics, using 2-ethyloxazoline as a comonomer. Cationic polymerizations can be conducted to producesoluble poly[2-(4-aminophenyl)oxazoline] and poly[2-(4-aminophenyl)-oxazoline-co-2-ethyloxazoline]. 相似文献
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Kristian Kempe Anja Baumgaertel Richard Hoogenboom Ulrich S. Schubert 《Journal of polymer science. Part A, Polymer chemistry》2010,48(22):5100-5108
New amphiphilic triblock copoly(2‐oxazoline)s, containing hydrophobic domains with fluorine‐containing blocks, were synthesized. Using microwave radiation as heating source, triblock copolymers with narrow molar mass distributions were obtained by the sequential addition of 2‐ethyl‐2‐oxazoline, 2‐(1‐ethylheptyl)‐2‐oxazoline, and 2‐(2,6‐difluorophenyl)‐2‐oxazoline. The polymers obtained were characterized by size exclusion chromatography, 1H NMR spectroscopy and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS). To investigate the incorporation of all three monomers into the triblock copolymers, a model polymer was prepared with shorter blocks exhibiting a suitable length to be measured in the reflector mode of a MALDI‐TOF MS. In addition, kinetic investigations on the homopolymerizations of all monomers were performed in nitromethane at 140 °C, yielding the polymerization rates under these conditions. DSC measurements of poly(2‐(1‐ethylheptyl)‐2‐oxazoline) and poly(2‐(2,6‐difluorophenyl)‐2‐oxazoline)) revealing glass transitions at about 33 and 120 °C, respectively. The thermal analysis of a blend of the two polymers showed two glass transitions revealing demixing, which could be an indicating for the immiscibility of the two components in the block copolymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
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Dr. Yong Guan Jonathan W. Attard Prof. Dr. Anita E. Mattson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(8):1742-1747
The stereocontrolled construction of biologically relevant chromanones and tetrahydroxanthones has been achieved through the addition of alkynes to benzopyrylium trilfates under the influence of copper bis(oxazoline) catalysis. Excellent levels of enantiocontrol (63–98 % ee) are achieved in the addition of a variety of alkynes to an array of chromenones with a hydrogen in the 2-position. Promising levels of enantiocontrol (54–67 % ee) are achieved in the alkynylation of chromenones with esters in the 2-position, generating tertiary ether stereocenters resembling those frequently found in naturally occurring metabolites. 相似文献
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Nakamura S Hirata N Yamada R Kita T Shibata N Toru T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(18):5519-5527
The enantioselective reactions of lithiated benzyl trifluoromethyl sulfones with a substoichiometric amount of a bis(oxazoline) and various aldehydes is disclosed. The products were formed with excellent diastereo- and enantioselectivities. Fluorination of the sulfone with N-fluorobenzenesulfonimide and a stoichiometric amount of a bis(oxazoline) gave products with extremely high enantioselectivities (up to 99% ee; ee=enantiomeric excess). The enantioselective reaction was confirmed to proceed through a dynamic thermodynamic resolution pathway. 相似文献
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Richard Hoogenboom Dr. 《Angewandte Chemie (International ed. in English)》2009,48(43):7978-7994
The living cationic ring‐opening polymerization of 2‐oxazolines has been studied in great detail since its discovery in 1966. The versatility of this living polymerization method allows copolymerization of a variety of 2‐oxazoline monomers to give a range of tunable polymer properties that enable, for example, hydrophilic, hydrophobic, fluorophilic, as well as hard and soft materials to be obtained. However, this class of polymers was almost forgotten in the 1980s and 1990s because of their long reaction times and limited application possibilities. In the new millennium, a revival of poly(2‐oxazoline)s has arisen because of their potential use as biomaterials and thermoresponsive materials, as well as the easy access to defined amphiphilic structures for (hierarchical) self‐assembly. Recent developments that illustrate the potential of poly(2‐oxazoline)s are discussed in this Review. In addition, the promising combination of poly(2‐oxazoline)s and click chemistry is illustrated. 相似文献
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Cornejo A Fraile JM García JI García-Verdugo E Gil MJ Legarreta G Luis SV Martínez-Merino V Mayoral JA 《Organic letters》2002,4(22):3927-3930
[formula: see text] A chiral pyridine-bis(oxazoline) ligand, functionalized with a vinyl group in the pyridine ring, can be polymerized with styrene and divinylbenzene to obtain supported chiral ligands. As proof of the usefulness of this supported ligands, the corresponding ruthenium complexes are catalysts for the cyclopropanation reaction of styrene with ethyl diazoacetate with up to 85% ee. 相似文献