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排序方式: 共有139条查询结果,搜索用时 15 毫秒
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Daniel C. Steigerwald Bardia Soltanzadeh Aritra Sarkar Cecilia C. Morgenstern Richard J. Staples Babak Borhan 《Chemical science》2021,12(5):1834
Intermolecular asymmetric haloamination reactions are challenging due to the inherently high halenium affinity (HalA) of the nitrogen atom, which often leads to N-halogenated products as a kinetic trap. To circumvent this issue, acetonitrile, possessing a low HalA, was used as the nucleophile in the catalytic asymmetric Ritter-type chloroamidation of allyl-amides. This method is compatible with Z and E alkenes with both alkyl and aromatic substitution. Mild acidic workup reveals the 1,2-chloroamide products with enantiomeric excess greater than 95% for many examples. We also report the successful use of the sulfonamide chlorenium reagent dichloramine-T in this chlorenium-initiated catalytic asymmetric Ritter-type reaction. Facile modifications lead to chiral imidazoline, guanidine, and orthogonally protected 1,2,3 chiral tri-amines.Intermolecular haloamination reactions are challenging due to the high halenium affinity of the nitrogen atom. This is circumvented by using acetonitrile as an attenuated nucleophile, resulting in an enantioselective halo-Ritter reaction. 相似文献
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Noah J. Tremblay Alon A. Gorodetsky Dr. Marshall P. Cox Theanne Schiros Dr. Bumjung Kim Rachel Steiner Zachary Bullard Aaron Sattler Woo‐Young So Dr. Yoshimitsu Itoh Dr. Michael F. Toney Dr. Hirohito Ogasawara Dr. Arthur P. Ramirez Prof. Ioannis Kymissis Dr. Michael L. Steigerwald Dr. Colin Nuckolls Prof. 《Chemphyschem》2010,11(4):742-742
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Dettmer K Nürnberger N Kaspar H Gruber MA Almstetter MF Oefner PJ 《Analytical and bioanalytical chemistry》2011,399(3):1127-1139
Trypsin/ethylenediaminetetraacetic acid (EDTA) treatment and cell scraping in a buffer solution were compared for harvesting
adherently growing mammalian SW480 cells for metabolomics studies. In addition, direct scraping with a solvent was tested.
Trypsinated and scraped cell pellets were extracted using seven different extraction protocols including pure methanol, methanol/water,
pure acetone, acetone/water, methanol/chloroform/water, methanol/isopropanol/water, and acid–base methanol. The extracts were
analyzed by GC-MS after methoximation/silylation and derivatization with propyl chloroformate, respectively. The metabolic
fingerprints were compared and 25 selected metabolites including amino acids and intermediates of energy metabolism were quantitatively
determined. Moreover, the influence of freeze/thaw cycles, ultrasonication and homogenization using ceramic beads on extraction
yield was tested. Pure acetone yielded the lowest extraction efficiency while methanol, methanol/water, methanol/isopropanol/water,
and acid–base methanol recovered similar metabolite amounts with good reproducibility. Based on overall performance, methanol/water
was chosen as a suitable extraction solvent. Repeated freeze/thaw cycles, ultrasonication and homogenization did not improve
overall metabolite yield of the methanol/water extraction. Trypsin/EDTA treatment caused substantial metabolite leakage proving
it inadequate for metabolomics studies. Gentle scraping of the cells in a buffer solution and subsequent extraction with methanol/water
resulted on average in a sevenfold lower recovery of quantified metabolites compared with direct scraping using methanol/water,
making the latter one the method of choice to harvest and extract metabolites from adherently growing mammalian SW480 cells. 相似文献
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Stanković S Catak S D'hooghe M Goossens H Abbaspour Tehrani K Bogaert P Waroquier M Van Speybroeck V De Kimpe N 《The Journal of organic chemistry》2011,76(7):2157-2167
The synthetic utility of N-alkylidene-(2,3-dibromo-2-methylpropyl)amines and N-(2,3-dibromo-2-methylpropylidene)benzylamines was demonstrated by the unexpected synthesis of 3-methoxy-3-methylazetidines upon treatment with sodium borohydride in methanol under reflux through a rare aziridine to azetidine rearrangement. These findings stand in contrast to the known reactivity of the closely related N-alkylidene-(2,3-dibromopropyl)amines, which are easily converted into 2-(bromomethyl)aziridines under the same reaction conditions. A thorough insight into the reaction mechanism was provided by both experimental study and theoretical rationalization. 相似文献
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Hannelore Vinek H. Völlenkle H. Nowotny 《Monatshefte für Chemie / Chemical Monthly》1970,101(1):275-284
Zusammenfassung Die Kristallstruktur von Pb3GeAl10O20 und der dazu isotypen Verbindung Pb3SiAl10O20 wird bestimmt (R=0,16). Die Gitterparameter der monoklinen, pseudorhombischen Zelle (Raumgruppe I2/m–C
2h
3
;Z=2) sind:a=14,39;b=11,44;c=5,004 Å und =90,0 für Pb3GeAl10O20 und:a=14,34;b=11,39;c=4,96 und =90,0 für Pb3SiAl10O20. Das Gerüst besteht aus AlO4-Tetraedern und AlO6-Oktaedern, wobei Germanium und Aluminium statistisch über die Plätze 2b, 4h, 8j und 8j verteilt sind. Die Bleiatome sitzen in Kanälen parallel zu [001] in 2a und 4i. Die verschiedene Umgebung der Pb-Atome auf den beiden Plätzen wird diskutiert.
Mit 2 Abbildungen 相似文献
The crystal structure of Pb3GeAl10O20 (Pb3SiAl10O20)
The crystal structure of Pb3GeAl10O20 and Pb3SiAl10O20, an isotypic compound, has been determined (R=0.16). The lattice parameters were found to be:a=14.39 Å;b=11.44 Å;c=5.004 Å, and =90.0 for Pb3GeAl10O20 and:a=14.34 Å;b=11.39 Å;c=4.96 Å and =90.0 for Pb3SiAl10O20;Z=2, space group I2/m–C3 2h. The network consists of AlO4 tetrahedra and AlO6 octahedra; germanium atoms are randomly distributed at the positions of the Al-atoms 2b, 4h, 8j, and 8j. The lead atoms occupy the positions 2a and 4i within channels in the network parallel to [001]. The different environment of the two kinds of lead atoms will be discussed.
Mit 2 Abbildungen 相似文献
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