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981.
Xukai Guan Dong An Guofeng Liu Heng Zhang Jigang Gao Tianyun Zhou Guangliang Zhang Suoqin Zhang 《Tetrahedron letters》2018,59(25):2418-2421
Chiral imidodiphosphoric acids were employed as catalysts for the enantioselective α-chlorination of β-keto esters and amides using NCS as the chlorine source, providing a series of optically active products with good to high enantioselectivities (74–95% ee) and excellent yields (92–99%). This represents the first report of the Brønsted acid catalyzed enantioselective α-chlorination of cyclic β-keto derivatives. 相似文献
982.
Two neutral five-membered pyridine-imine palladium complexes with the bulky dibenzhydryl (CH(Ph)2) substituted aniline were synthesized and fully characterized by nuclear magnetic resonance (NMR) and X-ray crystal diffraction.Well-defined cationic palladium complexes were further obtained by treatment of chloromethylpalladium complexes with sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate (NaBArF) in CH3CN.Cationic palladium complexes were capable of catalyzing ethylene oligomerization without any cocatalysts.The influences of catalyst structure,reaction temperature,and ethylene pressure on ethylene oligomerization were studied in detail.The introduction of bulky benzhydryl (CH(Ph)2) on the ortho position of the aniline moiety enhanced catalytic activity,thermal stability of the catalyst,and molecular weight of the obtained products.Highly branched oligomers with molecular weights of 600-800 g/mol and narrow polydispersities (1.03-1.12) were produced. 相似文献
983.
984.
Debilosides A–C ( 1 – 3 ), three new megastigmane glucosides, were isolated from the whole plant of Equisetum debile, together with the four known constituents blumenol A, corchoinoside C, sammangaoside A, and (3S,5R,6R,7E,9S)‐9‐[(β‐D ‐glucopyranosyl)oxy]megastigm‐7‐ene‐3,5,6‐triol ( 4 ). Their structures were elucidated on the basis of in‐depth spectroscopic analyses including 2D‐NMR techniques. 相似文献
985.
本文对1-N-甲基-苯并哒嗪TCNQ复合物(1-N-M_(ci) TCNQ_2)和2-N-甲基-苯并哒嗪TCNQ复合物(2-N-M_(ci) TCNQ_2)的晶体中排列进行堆积分析, 采用OPEC程序计算它们的堆积能。1-N-M_(ci) TCNQ_2的堆积能为-70.194 kcal mol~(-1), 2-N-M_(ci) TCNQ_2的堆积能为-66.945 kcal mol~(-1)。结果表明, 在这两种TCNQ复合物中, 给体分子的各向尺寸的差异小, 则对TCNQ排列的影响小, 有利于TCNQ分子排列成一维的柱子。 相似文献
986.
土壤中锰的形态分析方法研究 总被引:2,自引:0,他引:2
采用Tessler的连续浸取程序,利用La-Zr涂履石墨管,石墨炉原子吸收光谱对土壤中不同形态锰的浸取与测定的条件进行了研究。经过对土样-3各形态的浸取液进行加标试验,其回收率在90%-110%,测定了一组土样,结果满意。 相似文献
987.
Anodized Iron Oxide Nanostructures on Different Carbon Steels for Photoelectrochemical Water Splitting
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In this study, two different nanostructural iron oxide films were prepared on two kinds of carbon steels (CS) with different contents of impurities via anodization in a mixture of aqueous ammonium fluoride solution and ethylene glycol, respectively, and apply to photoelectrochemical (PEC) water splitting. After annealing, iron oxide nanotubes (NTs) was coated on surface of lower purity CS and iron oxide nanoporous (NPs) was coated on surface of higher purity CS via scanning electron microscope. X‐ray diffraction pattern shows both of samples contain a major phase of α‐Fe2O3 and a slight phase of Fe3O4. Compared with NPs, NTs behaves better absorbance ability in visible spectra range via UV‐visible absorbance spectra. From PEC response, the iron oxide NTs showed higher water splitting performance (0.10 mA/cm2 at 0.4 V vs. Ag/AgCl) than NPs (0.04 mA/cm2 at 0.4 V vs. Ag/AgCl) due to better absorbance, higher car‐ rier concentration and low charge transfer resistance. 相似文献
988.
A novel functional diamine N12, containing triphenylamine moiety, biphenyl, tert-butyl substituents and long alkyl chain, N,N-bis(4-aminophenyl)-p-(3,5-di-tert-butyl-4-dodecyloxy phenyl) aniline (N12), was synthesised and characterised. A series of polyimides (PIs) were prepared based on 2,2?-bis(trifluoromethyl)benzidine, 4,4?-oxydiphthalicanhydride and different contents of N12 via a conventional two-step procedure that included a ring-opening polyaddition to gain polyamic acids, followed by chemical cyclodehydration. The chemical structures of the intermediates, diamines and PIs were characterised by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. All of the PIs were amorphous and exhibited good solubility in both polar aprotic solvents and some low boiling point solvents. PIs containing different content of N12 could induce highly uniform vertical alignment of liquid crystals (LCs). More importantly, PIs derived from N12 showed a good rubbing resistance. Besides, all PI films showed high transmittance in the wavelength range 400–700 nm and good thermal stabilities. Such PIs could be suitable candidates for alignment layers used in the manufacture of high-performance vertical alignment mode LC displays. 相似文献
989.
Yee Kiat Heng Thiam Seng Colin Theng Hong Liang Tey Ee Chee Ren Wei‐Sheng Chong 《Photochemistry and photobiology》2016,92(2):355-359
Studies have reported the association of human leukocyte antigen (HLA) genes with susceptibility to develop actinic prurigo (AP) in Caucasians, but there were no studies in Asian populations, including the Chinese. Our study was performed to determine if AP is associated with susceptibility or protective HLA alleles or haplotypes in Singaporean Chinese. All Chinese patients diagnosed with AP at National Skin Center, Singapore, from January 2002 to April 2015 were invited to participate in the study. Clinical data and phototesting results were collated, and HLA typing was performed. Among 14 patients included, 11 were male and the mean age was 49.6 (37.9–61.3) years. All patients did not have a family history of AP and none had mucosal involvement, as such these clinical features differed from Caucasian AP patients. The frequency of DRB1*03:01 in AP patients was significantly higher compared to healthy controls (43% vs 16%, P = 0.022, odds ratio (OR) 3.89). Concurrently, the frequency of HLA‐B*58:01‐DRB1*03:01 haplotype was also significantly increased (25% vs 7%, P = 0.004, OR 4.23). In conclusion, HLA‐DRB1*03:01 was associated with AP in Singaporean Chinese patients. This novel allelic association may possibly be utilized as a biological marker to aid in the diagnosis of AP in Chinese patients. 相似文献
990.