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881.
[reaction: see text] A novel metal-free approach to the alkyne amidation reaction is presented. The oxidation of properly substituted amides by the hypervalent iodine reagent PIFA provides the generation of a nitrenium ion that can react intramolecularly with a triple bond, leading to the construction of the title compounds. 相似文献
882.
Madhavan Nampoothiri K Roopesh K Chacko S Pandey A 《Applied biochemistry and biotechnology》2005,120(2):97-108
Escherichia coli NCIM 2569 was evaluated for its potential for amidase production under submerged fermentation. Among the various amide compounds
screened, maximum substrate specificity and enzyme yield (8.1 U/mL) were obtained by using 1% acetamide. Fermentation was
carried out at 30°C in shake-flask culture under optimized process conditions. A maximum of 0.52 U/mL of intracellular amidase
activity was also obtained from cells incubated for 24 h. Studies were also performed to elucidate the optimal conditions
(gel concentration, initial biomass, curing period of beads, and calcium ion concentration in the production medium) for immobilization
of whole cells. By using E. coli cells entrapped in alginate, a maximum of 6.2 U/mL of enzyme activity was obtained after 12 h of incubation under optimized
conditions. Using the immobilized cells, three repeated batches were carried out successfully, and 85% of the initial enzyme
activity was retained in the second and third batches. The study indicated that the immobilized E. coli cells offered certain advantages such as less time for maximum enzyme production, more stability in the enzyme production
rate, and repeated use of the biocatalyst. 相似文献
883.
Ferrimagnetic nanogranular Co3O4 through solvothermal decomposition of colloidally dispersed monolayers of alpha-cobalt hydroxide 总被引:1,自引:0,他引:1
Nethravathi C Sen S Ravishankar N Rajamathi M Pietzonka C Harbrecht B 《The journal of physical chemistry. B》2005,109(23):11468-11472
Co3O4 nanoparticles of 35 nm with a cauliflower-like morphology were obtained when a monolayer colloidal dispersion of dodecyl sulfate intercalated alpha-cobalt hydroxide in butanol was subjected to solvothermal hydrolytic decomposition. The nanogranular particles exhibit weakly ferromagnetic properties in contrast with both bulk and dispersed nanoparticulate Co3O4. 相似文献
884.
A protected aldehyde-functionalized 2-oxazoline, 2-[3-(1,3)-dioxolan-2-ylpropyl]-2-oxazoline (DPOx), was synthesized from commercially available compounds in high yields. The polymerization of DPOx with different initiators proceeds via a living ionic mechanism; thus, the polymers were of low polydispersity and the degree of polymerization could be precisely adjusted. Copolymerization with 2-methyl-2-oxazoline gave water-soluble statistical copolymers. Hydrolysis of the homo- and copolymers resulted in well-defined, aldehyde-bearing poly(2-oxazoline)s. The aldehyde side functions reacted quantitatively with an amino-oxy compound to form the corresponding oxime. 相似文献
885.
886.
Servili M Selvaggini R Esposto S Taticchi A Montedoro G Morozzi G 《Journal of chromatography. A》2004,1054(1-2):113-127
Hydrophilic phenols are the most abundant natural antioxidants of virgin olive oil (VOO), in which, however, tocopherols and carotenes are also present. The prevalent classes of hydrophilic phenols found in VOO are phenolic alcohols, phenolic acids, flavonoids, lignans and secoiridoids. Secoiridoids, that include aglycon derivatives of oleuropein, demethyloleuropein and ligstroside, that are present in olive fruit, are the most abundant phenolic antioxidants of VOO. The sensory and healthy proprieties of VOO hydrophilic phenols as well as the agronomic and technological parameters that affect their concentration in the oil are discussed in this paper. 相似文献
887.
Sonia Acinas 《Numerical Functional Analysis & Optimization》2016,37(11):1339-1353
In this article, we consider the best multivalued polynomial approximation operator, defined in an Orlicz Space LΦ(B), and its extension to Lφ(B), where φ is the derivative of Φ which is not an N-function. Thus, the extension of the best polynomial approximation operator from L1(B) to L0(B) arises as a particular case of this work, taking Φ(x) = x. 相似文献
888.
Dr. Jean‐Nicolas Desrosiers Liana Hie Dr. Soumik Biswas Dr. Olga V. Zatolochnaya Dr. Sonia Rodriguez Dr. Heewon Lee Dr. Nelu Grinberg Dr. Nizar Haddad Dr. Nathan K. Yee Prof. Neil K. Garg Dr. Chris H. Senanayake 《Angewandte Chemie (International ed. in English)》2016,55(39):11921-11924
A nickel‐catalyzed Heck cyclization for the construction of quaternary stereocenters is reported. This transformation is demonstrated in the synthesis of 3,3‐disubstituted oxindoles, which are prevalent motifs seen in numerous biologically active molecules. The method shows broad scope, proceeds in synthetically useful yields, and provides a rare means to construct stereochemically complex frameworks by nonprecious‐metal catalysis. 相似文献
889.
García ME Melón S Ruiz MA López R Sordo T Marchiò L Tiripicchio A 《Inorganic chemistry》2008,47(22):10644-10655
The reaction of Na[RuCp(CO) 2] with [MnCp'(CO) 2(NO)]BF 4 gives the corresponding heterometallic derivative [MnRuCpCp'(mu-CO) 2(CO)(NO)] (Cp = eta (5)-C 5H 5; Cp' = eta (5)-C 5H 4Me). In contrast, the group 6 metal carbonyl anions [MCp(CO) 2L] (-) (M = Mo, W; L = CO, P(OMe) 3, PPh 3) react with the Mn and Re complexes [M'Cp'(CO) 2(NO)]BF 4 to give the heterometallic derivatives [MM'CpCp'(mu-N)(CO) 3L] having a nitride ligand linearly bridging the metal centers (W-N = 1.81(3) A, N-Re = 1.97(3) A, W-N-Re = 179(1) (o), in [WReCpCp'(mu-N)(CO) 3{P(OMe) 3}]). Density-functional theory calculations on the reactions of [WCp(CO) 3] (-) and [RuCp(CO) 2] (-) with [MnCp(CO) 2(NO)] (+) revealed a comparable qualitative behavior. Thus, two similar and thermodynamically allowed reaction pathways were found in each case, one implying the displacement of CO from the cation and formation of a metal-metal bond, the other implying the cleavage of the N-O bond of the nitrosyl ligand and release of a carbonyl from the anion as CO 2. The second pathway is more exoergonic and is initiated through an orbitally controlled attack of the anion on the N atom of the NO ligand in the cation. In contrast, the first pathway is initiated through a charge-controlled attack of the anion to the C atom of a CO ligand in the cation. The CO 2-elimination pathway requires at the intermediate stages a close approach of the NO and CO ligands, which is more difficult for the Ru compound because of its lower coordination number (compared to W). This effect, when combined with a stronger stabilization of the initial intermediate in the Ru reaction, makes the CO 2-elimination pathway slower in that case. 相似文献
890.
Llusar R Triguero S Polo V Vicent C Gómez-García CJ Jeannin O Fourmigué M 《Inorganic chemistry》2008,47(20):9400-9409
A general route for the preparation of a series of dianionic Mo3S7 cluster complexes bearing dithiolate or diselenolate ligands, namely, [Mo3S7L3](2-) (where L = tfd (bis(trifluoromethyl)-1,2-dithiolate) (4(2-)), bdt (1,2-benzenedithiolate) (5(2-)), dmid (1,3-dithia-2-one-4,5-dithiolate) (6(2-)), and dsit (1,3-dithia-2-thione-4,5-diselenolate) (7(2-))) is reported by direct reaction of [Mo3S7Br6](2-) and (n-Bu)2Sn(dithiolate). The redox properties, molecular structure, and electronic structure (BP86/VTZP) of the 4(2-) to 7(2-) clusters have also been investigated. The HOMO orbital in all complexes is delocalized over the ligand and the Mo3S7 cluster core. Ligand contributions to the HOMO range from 61.67% for 4(2-) to 82.07% for 7(2-), which would allow fine-tuning of the electronic and magnetic properties. These dianionic clusters present small energy gaps between the HOMO and HOMO-1 orbitals (0.277-0.104 eV). Complexes 6(2-) and 7(2-) are oxidized to the neutral state to afford microcrystalline or amorphous fine powders that exhibit semiconducting behavior and present antiferromagnetic exchange interactions. These compounds are new examples of the still rare single-component conductors based on cluster magnetic units. 相似文献