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排序方式: 共有76条查询结果,搜索用时 11 毫秒
1.
Carina I. Jette Irina Geibel Shoshana Bachman Masaki Hayashi Shunya Sakurai Hideki Shimizu Jeremy B. Morgan Brian M. Stoltz 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(13):4341-4345
Herein, we report the first Pd‐catalyzed enantioselective arylation of α‐substituted γ‐lactams. Two sets of conditions were developed for this transformation, allowing for the use of either aryl chlorides or bromides as electrophiles. Utilizing a highly electron‐rich dialkylphosphine ligand we have been able to construct α‐quaternary centers in good yields (up to 91 % yield) and high enantioselectivities (up to 97 % ee). 相似文献
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P. Walter J. H. Brunn H. Schanz W. F. Bruce W. Bach K. Suzuki F. E. Raurich-Sas E. Busse P. Görlich A. H. Furnstal J. M. Voith G. B. Bachman und J. Hudig 《Fresenius' Journal of Analytical Chemistry》1936,107(5-6):201-205
Ohne Zusammenfassung 相似文献
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Thermally Rearranged Polymer Membranes Containing Tröger's Base Units Have Exceptional Performance for Air Separations 下载免费PDF全文
Stephen M. Meckler Dr. Jonathan E. Bachman Benjamin P. Robertson Chenhui Zhu Prof. Jeffrey R. Long Dr. Brett A. Helms 《Angewandte Chemie (International ed. in English)》2018,57(18):4912-4916
The influence of segmental chain motion on the gas separation performance of thermally rearranged (TR) polymer membranes is established for TR polybenzoxazoles featuring Tröger's base (TB) monomer subunits as exceptionally rigid sites of contortion along the polymer backbone. These polymers are accessed from solution‐processable ortho‐acetate functionalized polyimides, which are readily synthesized as high‐molecular‐weight polymers for membrane casting. We find that thermal rearrangement leads to a small increase in d‐spacing between polymer chains and a dramatic pore‐network reconfiguration that increases both membrane permeability and O2/N2 selectivity, putting its performance above the 2015 upper bound. 相似文献
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We report a diffraction-based, label-free biosensor on the surface of a planar optical waveguide. By selectively immobilizing proteins on an optical waveguide, the proteins can form the ridge/valley of a latent image optical grating. Binding events with patterned surface proteins dynamically increase grating height and cause an increase in light coupling out of the waveguide. We demonstrate the efficacy of this strategy for protein detection and present the design and fabrication of a device. 相似文献
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Bachman RE Zucchero AJ Robinson JL 《Langmuir : the ACS journal of surfaces and colloids》2012,28(1):27-30
A twin-tailed glutamate-based lipid with a pyridine headgroup was prepared in good yield using standard amide coupling and protection/deprotection chemistry. The resulting Lewis basic lipid gels a wide array of hydrocarbon solvents at a critical gelation concentration (C(g)) of 0.3 wt %. The gelation of more polar solvents, such as ethanol, THF, dichloromethane, and chloroform, occurs with a C(g) of between 2 and 5 wt %, demonstrating the importance of hydrogen bonding interactions in gel formation. The importance of hydrogen bonding in this system was also demonstrated by IR observation of the amide bands, which show a substantial shift upon gelation. Solutions of this new organogelator with concentrations below C(g) rapidly form gels upon the introduction of a wide variety of metal salts or complexes, providing a convenient general method for the preparation of metallogelators. Spectroscopic evidence suggests that the enhanced gelation seen in the metal-containing systems can be explained by a cross-linking of gel fibril aggregates similar to those formed by the unmetalated gelator. 相似文献
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In [2] E. Dobrowolski and K.S. Williams considered a problem of obtaining estimates for the sum
n=a+1
a+N
f(n),for a certain class of functions f. One specific application of their result is a new method for estimating character sums. In particular, they obtain a form of the Pólya-Vinogradov inequality with the constant 1/(2 log 2). In this note we improve their estimates and obtain, in particular, a form of the Pólya-Vinogradov inequality with the constant 1/(3 log 3). A nice feature of our estimate is that it is obtained by a very simple argument. 相似文献