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11.
Copolymerization of two monomers, 2-methyl-2-oxazoline (1) and itaconic acid (2) was carried out. The copolymerization proceeded spontaneously in 1:1 monomer feed ratio to give 2:1 copolymer 3. The mechanism for the production of such a 2:1 copolymer was explained by the in situ formation of monomer 5 from 1 and 2. Then, the propagation proceeded between 5 and 1 via zwitterionic intermediates. When the ratio of 1 in the feed was higher, the homopropagation of 1 took place. 相似文献
12.
Murty A.R.C. Bulusu Peter Waldstätten Thomas Tricotett Gerhard Schulz 《Tetrahedron letters》2004,45(12):2527-2530
A novel photochemical amide cleavage reaction of (6S)-methoxyascomycin opening a pathway for the selective cleavage of the pipecolic acid, is described. The scope of this reaction with several analogues carrying suitable protecting groups is examined. 相似文献
13.
Versatile synthesis of some analogues of the naturally-occurring α-glucosidase inhibitor salacinol (1), involving thioanhydro alditol moieties with erythro, d,l-threo, xylo, ribo, d-arabino and d-manno configurations is described. Nucleophilic attack at the least-hindered carbon atom of an l- or d-protected erythritol cyclic sulfate by the thioanhydro alditol sulfur atom yielded the desired zwitterionic compounds. In addition, the preparation of the cyclic sulfates of 2,4-O-benzylidene-d-erythritol and 2,4-O-isopropylidene-l-erythritol was improved. Enzyme inhibition tests showed that most of the new compounds were weak but specific inhibitors, while good inhibitory activity was found for a six-membered ring analogue (β-glucosidase: Ki=16 μM). 相似文献
14.
Ysaura De Sanctis Alejandro J. Arce Ruben Machado Teresa González 《Journal of organometallic chemistry》2004,689(11):2025-2028
The cluster [Os3(CO)10(MeCN)2] reacts readily with azulene in refluxing cyclohexane to give the oxidative addition product [Os3(μ-H)(μ2-η1-C10H7)(CO)10] 1 which was shown by its X-ray crystal structure to contain the C5 ring of the azulenyl ligand bonded through a single carbon atom at the 1-position. We propose that the compound is zwitterionic, with the 7-membered ring a tropylium cation and the 5-membered ring coordinated as a μ-alkylidene to the metal cluster, which carries a formal negative charge. Thermal loss of one CO ligand leads by further oxidative addition to the known cluster [Os3(μ-H)2(μ3-η1:η1:η1-C10H6)(CO)9] 2. 相似文献
15.
Raghupathi Mutyala Venkatram R. Reddy Ravikiran Donthi V.S. Ramakrishna Kallaganti Rajesh Chandra 《Tetrahedron letters》2019,60(10):703-706
The enantioselective synthesis of the tetrahydropyranopyrazole scaffold has been achieved. The quinidine catalyzed reaction of allenoates with arylidenepyrazolones proceeded with high enantio- and diastereoselectivity while the reactions of alkylidenepyrazolones were less efficient. Allene ketones also afforded tetrahydropyranopyrazole derivatives in high yields, however, with only moderate enantioselectivity. The primary adduct undergoes further functional group transformations without effecting the initially formed chiral centre. 相似文献
16.
A.T. Myller 《Applied Surface Science》2010,257(5):1616-1622
Titanium dioxide (TiO2) powder was chemically modified with 2-aminoethyl dihydrogen phosphate (AEPH2) and with 2-aminoethyl hydrogen ammonium phosphate (AEPHNH4) in order to achieve an aminofunctionalized high-surface-area TiO2 carrier suitable for more complex functionalizing. AEPH2 was found to form the monoammonium salt AEPHNH4 with ammonium ion rather than the diammonium salt AEP(NH4)2. The AEPHNH4 was thoroughly characterized by various techniques and compared with AEPH2. Bonding of AEPH2 and AEPHNH4 with TiO2 powder was studied. According to the 31P NMR and elemental analysis results, AEPH2 and AEPHNH4 form covalent chelate bidentate bonds between the phosphate group and the TiO2, while the amino groups remain accessible, creating uniform aminofunctionalized TiO2 surface fully occupied by AEP groups. Amount of AEP groups on TiO2 was limited to 1.5 wt-%. 相似文献
17.
Petr Švec Zdeňka Padělková Jaroslav Hole?ek 《Journal of organometallic chemistry》2010,695(23):2475-2485
The C,N-chelated tri and diorganotin(IV) chlorides react with both protic mineral acids and carboxylic acids. The nitrogen atom of the LCN ligand (where LCN is 2-(dimethylaminomethyl)phenyl) is thus quarternized - protonated and new Sn-X bond (X = Cl, Br, I or the remainder of the starting acid used) is simultaneously formed. The set of zwitterionic tri and diorganostannates containing protonated 2-(dimethylaminomethyl)phenyl-moiety was prepared and structurally characterized by multinuclear NMR spectroscopy and XRD techniques. In all these cases, the intramolecular N-H?X bond is present in the molecule. Despite the central tin atom remains five-coordinated (except for the [HLCNH]+[(n-Bu)2SnCl(NO3)2]−) and reveals a distorted trigonal bipyramidal geometry, the 119Sn NMR chemical shift values of these zwitterionic stannates are somewhat shifted to the higher field than corresponding starting C,N-chelated tri and diorganotin(IV) halides. Reactions of C,N-chelated organotin(IV) halides with various Lewis acids are also discussed. 相似文献
18.
Jan Cz. Dobrowolski Joanna E. Rode Joanna Sadlej 《Journal of Molecular Structure》2007,810(1-3):129-134
Based on the B3LYP and MP2/aug-cc-pVDZ calculations, 51 cysteine conformers were found to be stable in the gas phase. The calculations were repeated for the most stable eight structures by using the aug-cc-pVTZ basis set. To estimate the influence of water on the cysteine conformation, the IEF-PCM/B3LYP/aug-cc-pVDZ calculations were carried out and showed 44 neutral and 12 zwitterion conformers to be stable in the water solution. The most stable cysteine structure in water appeared to be the zwitterionic conformer quite similar to the molecule observed in the crystal state. 相似文献
19.
《Journal of Coordination Chemistry》2012,65(13):2274-2283
The synthesis and characterization of a new Sr(II) coordination polymer (CP), [Sr(H2O)(H-gly)2Cl2] n (1) (H-gly?=?glycine), is described. Compound 1 crystallizes in the centrosymmetric orthorhombic space group Pcnb and its structure consists of a central Sr(II), a water molecule, a zwitterionic glycine, and a chloride. The central metal is nine coordinate, bonded to six oxygens from four different bridging H-gly ligands, two symmetry-related chlorides, and a terminal water molecule. The μ2-tridentate bridging zwitterionic glycine results in the formation of a 1-D CP with an Sr···Sr separation of 4.560?Å across the chain. The chloride, H-gly, and coordinated water are involved in five varieties of hydrogen bonding. A comparative study of the structural chemistry of several alkaline-earth glycine compounds is described. 相似文献
20.