排序方式: 共有86条查询结果,搜索用时 15 毫秒
41.
Dr. Saad Shaaban Caitlin Davies Prof. Dr. Christian Merten Jana Flegel Felix Otte Prof. Dr. Carsten Strohmann Prof. Dr. Herbert Waldmann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(47):10729-10734
RhIII-catalyzed C−H functionalization reaction yielding isoindolinones from aryl hydroxamates and ortho-substituted styrenes is reported. The reaction proceeds smoothly under mild conditions at room temperature, and tolerates a range of functional groups. Experimental and computational investigations support that the high regioselectivity observed for these substrates results from the presence of an ortho-substituent embedded in the styrene. The resulting isoindolinones are valuable building blocks for the synthesis of bioactive compounds. They provide easy access to the natural-product-like compounds, isoindolobenzazepines, in a one-pot two-step reaction. Selected isoindolinones inhibited Hedgehog (Hh)-dependent differentiation of multipotent murine mesenchymal progenitor stem cells into osteoblasts. 相似文献
42.
A convenient and efficient method for the synthesis of N1-substituted orotic acid derivatives is reported. The synthetic route utilizes substituted maleimide as synthetic intermediate and takes only four simple steps from readily available starting materials. As a result, orotic acid derivatives with various alkyl and aromatic groups at N1 can be readily synthesized. 相似文献
43.
Robert A. Kowtoniuk Tao Pei Caitlin M. DeAngelo Jacob H. Waldman Erin N. Guidry J. Michael Williams Robert M. Garbaccio Stephanie E. Barrett 《Journal of polymer science. Part A, Polymer chemistry》2014,52(10):1385-1391
l ‐Ornithine‐based poly(peptides) have been widely utilized in the field of drug delivery, however few studies have been conducted examining the details of polymerization. In this article, the effects of monomer concentration, polymerization kinetics, polymer molecular weight and monomer purity were investigated using l ‐carboxybenzyl (Cbz)‐ornithine as a model monomer. The mechanism of polymerization herein follows the normal amine mechanism to produce poly(peptides) having controlled molecular weights, known chain ends and a narrow polydispersity index (PDI). A preferred monomer concentration range was determined, which required minimal polymerization times and allowed for predictable and reproducible molecular weights with narrow PDIs. The impact of monomer purity on the polymerization was established and monomer purification conditions are reported, which produce high‐purity monomer after a single recrystallization. Additionally, the optimized polymerization conditions and monomer purification protocol were combined with a sequential monomer addition technique to produce high molecular weight poly(ornithine) with a narrow PDI and known chain ends. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1385–1391 相似文献
44.
Patrick L. Hanks Caitlin A. Forschner Douglas R. Lloyd 《Journal of membrane science》2008,322(1):91-97
An established sieve mechanism model for microfiltration was modified to incorporate elliptical pore shapes that arise from uni-axial elongation of track-etch (TE) membranes. The particular membranes investigated were poly(ethylene teraphthalate) TE membranes with an average pore size of 0.6 μm and elongations up to 35.6%. The modified sieve theory predicts that a membrane that has undergone a 35.6% elongation allows for twice the throughput compared to the original membrane with circular pores, while maintaining the same removal ability for a solution containing 1 μm particles. 相似文献
45.
Dr. Lauren K. Macreadie Dr. Ravichandar Babarao Caitlin J. Setter Seok J. Lee Dr. Omid T. Qazvini Dr. Aaron J. Seeber Dr. John Tsanaktsidis Prof. Shane G. Telfer Prof. Stuart R. Batten Prof. Matthew R. Hill 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(15):6146-6154
The resurgence of interest in the hydrogen economy could hinge on the distribution of hydrogen in a safe and efficient manner. Whilst great progress has been made with cryogenic hydrogen storage or liquefied ammonia, liquid organic hydrogen carriers (LOHCs) remain attractive due to their lack of need for cryogenic temperatures or high pressures, most commonly a cycle between methylcyclohexane and toluene. Oxidation of methylcyclohexane to release hydrogen will be more efficient if the equilibrium limitations can be removed by separating the mixture. This report describes a family of six ternary and quaternary multicomponent metal–organic frameworks (MOFs) that contain the three-dimensional cubane-1,4-dicarboxylate (cdc) ligand. Of these MOFs, the most promising is a quaternary MOF (CUB-30), comprising cdc, 4,4′-biphenyldicarboxylate (bpdc) and tritopic truxene linkers. Contrary to conventional wisdom that adsorptive interactions with larger, hydrocarbon guests are dominated by π–π interactions, here we report that contoured aliphatic pore environments can exhibit high selectivity and capacity for LOHC separations at low pressures. This is the first time, to the best of our knowledge, where selective adsorption for cyclohexane over benzene is witnessed, underlining the unique adsorptive behavior afforded by the unconventional cubane moiety. 相似文献
46.
Sarah Spence Adams Matthew Crawford Caitlin Greeley Bryce Lee Mathav Kishore Murugan 《Designs, Codes and Cryptography》2009,51(3):245-252
Multilevel Hadamard matrices (MHMs), whose entries are integers as opposed to the traditional restriction to {±1}, were introduced
by Trinh, Fan, and Gabidulin in 2006 as a way to construct multilevel zero-correlation zone sequences, which have been studied
for use in approximately synchronized code division multiple access systems. We answer the open question concerning the maximum
number of distinct elements permissible in an order n MHM by proving the existence of an order n MHM with n elements of distinct absolute value for all n. We also define multidimensional MHMs and prove an analogous existence result.
相似文献
47.
The sodium periodate mediated oxidative cleavage of the C-C bond of 12 epoxides is reported with yields of the corresponding carbonyl compounds in up to 91%. This is a two-step reaction that proceeds through a rate-limiting epoxide opening to a vicinal diol that is cleaved in situ to the corresponding carbonyl compound. This method serves as a chemoselective alternative to ozonolysis. 相似文献
48.
49.
Lauren K. Macreadie Ravichandar Babarao Caitlin J. Setter Seok J. Lee Omid T. Qazvini Aaron J. Seeber John Tsanaktsidis Shane G. Telfer Stuart R. Batten Matthew R. Hill 《Angewandte Chemie (International ed. in English)》2020,59(15):6090-6098
The resurgence of interest in the hydrogen economy could hinge on the distribution of hydrogen in a safe and efficient manner. Whilst great progress has been made with cryogenic hydrogen storage or liquefied ammonia, liquid organic hydrogen carriers (LOHCs) remain attractive due to their lack of need for cryogenic temperatures or high pressures, most commonly a cycle between methylcyclohexane and toluene. Oxidation of methylcyclohexane to release hydrogen will be more efficient if the equilibrium limitations can be removed by separating the mixture. This report describes a family of six ternary and quaternary multicomponent metal–organic frameworks (MOFs) that contain the three‐dimensional cubane‐1,4‐dicarboxylate (cdc) ligand. Of these MOFs, the most promising is a quaternary MOF (CUB‐30), comprising cdc, 4,4′‐biphenyldicarboxylate (bpdc) and tritopic truxene linkers. Contrary to conventional wisdom that adsorptive interactions with larger, hydrocarbon guests are dominated by π–π interactions, here we report that contoured aliphatic pore environments can exhibit high selectivity and capacity for LOHC separations at low pressures. This is the first time, to the best of our knowledge, where selective adsorption for cyclohexane over benzene is witnessed, underlining the unique adsorptive behavior afforded by the unconventional cubane moiety. 相似文献
50.
Caitlin Howell Anne Christine Steenkjær Hastrup Rory Jara Flemming Hofmann Larsen Barry Goodell Jody Jellison 《Cellulose (London, England)》2011,18(5):1179-1190
The effect of hot-water extraction and two types of fungal decay, brown rot and white rot, on wood crystalline cellulose structure
was examined using a combination of X-ray diffraction (XRD) and 13C solid-state nuclear magnetic resonance (NMR) spectroscopy. Although having opposite effects on the overall crystallinity
of the wood, the XRD results revealed that both extraction and brown-rot decay caused a significant decrease in the 200 crystal
plane spacing (d-spacing) not seen for the white-rotted samples. This effect was found to be additive, as samples that were first extracted,
then decayed showed a double decrease in d-spacing compared to that caused by extraction alone. This suggested that, despite having a similarly directed effect on the
spacing of the crystalline planes, the two treatment methods facilitate a decrease in d-spacing in different ways. NMR results support the conclusion of differing structural effects, suggesting that the hot-water
extraction procedure was causing a co-crystallization of existing crystalline domains, while the brown rot decay was depolymerizing
the cellulose chains of the crystals, possibly allowing the remaining crystalline material the freedom to relax into a more
energetically favorable, tightly packed state. These findings could have important implications for those seeking to understand
the effects of modification treatments or biodegradation of crystalline cellulose nanostructures in their native states. 相似文献