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11.
Bivas Mondal Rakesh Maiti Xing Yang Jun Xu Weiyi Tian Jia-Lei Yan Xiangyang Li Yonggui Robin Chi 《Chemical science》2021,12(25):8778
4,5-Dihydropyridazinones bearing an aryl substituent at the C6-position are important motifs in drug molecules. Herein, we developed an efficient protocol to access aryl-dihydropyridazinone molecules via carbene-catalyzed asymmetric annulation between dinucleophilic arylidene hydrazones and bromoenals. Key steps in this reaction include polarity-inversion of aryl aldehyde-derived hydrazones followed by chemo-selective reaction with enal-derived α,β-unsaturated acyl azolium intermediates. The aryl-dihydropyridazinone products accessed by our protocol can be readily transformed into drugs and bioactive molecules.Polarity inversion of arylidene hydrazones to react with bromoenals via carbene organic catalysis is disclosed. The reaction enantioselectively affords 6-aryl-4,5-dihydropyridazinones and related drugs with proven commercial applications. 相似文献
12.
Conrad Newton Per Osland Tai Tsun Wu 《Zeitschrift fur Physik C Particles and Fields》1994,61(3):441-447
As a method of regularization, point splitting has played an essential role in the recent theoretical determination of the masses of the Higgs boson and the top quark. It is the purpose of this paper to put this pointsplitting regularization on a firm basis. The result turns out to be extremely simple: replace the usual vertex factor-ieγ µ in quantum electrodynamics by $$ - ie(\gamma _\mu - \frac{{\not p}}{{p \cdot \delta }}\delta _\mu ),$$ wherep is the momentum of the photon line, andδ µ is the distance for point splitting. No additional vertices are needed. 相似文献
13.
14.
Synthesis and characterization of 6-O-acyl-2-O-alpha-D-glucopyranosyl-L-ascorbic acids with a branched-acyl chain 总被引:3,自引:0,他引:3
We previously reported the chemical synthesis of a series of novel monoacylated vitamin C derivatives, 6-O-acyl-2-O-alpha-D-glucopyranosyl-L-ascorbic acids (6-Acyl-AA-2G) possessing a straight-acyl chain of varying length from C(4) to C(18), as effective skin antioxidants. In this paper, we describe branched type of 6-Acyl-AA-2G derivatives (6-bAcyl-AA-2G) synthesized by use of a 2-branched-chain fatty acid anhydride as an acyl donor. The stability of 6-bAcyl-AA-2G in neutral solution was much higher than that of 6-Acyl-AA-2G, while they were susceptible to enzymatic hydrolysis for exerting vitamin C effect. These branched derivatives as well as 6-Acyl-AA-2G increased the radical scavenging activity against 1, 1-diphenyl-2-picrylhydrazyl and the lipophilicity in octanol/water-partitioning systems with increasing length of their acyl group. In addition, the 6-bAcyl-AA-2G derivative with an acyl chain of C(12), 6-bDode-AA-2G had the excellent solubility to various solvents, suggesting easy handling in cosmetic use. These characteristics of 6-bAcyl-AA-2G may be available for skin care application as an effective antioxidant. 相似文献
15.
Y2O3, La2O3, Sm2O3对氧化铝瓷烧结及力学性能的影响 总被引:16,自引:3,他引:16
研究了3种稀土氧化物对氧化铝陶瓷烧结性能和力学性能的影响.结果表明 含Y2O3,La2O3,Sm2O3的添加剂促进了氧化铝瓷的烧结,提高了氧化铝瓷的力学性能.Y2O3和Sm2O3掺量为0.50%,La2O3掺量为0.75%时氧化铝瓷在1600或1620 ℃保温2 h烧结,相对密度达98.9%以上,强度超过439 MPa,断裂韧性达5.15 MPa·m1/2以上.微观结构分析表明,Y2O3,La2O3,Sm2O3抑止氧化铝晶粒生长,细化晶粒,使晶粒尺寸较均匀形成致密化结构. 相似文献
16.
Diclobutrazol的合成及其生物活性研究张洪奎,廖联安,陈明德,叶向阳,郭奇珍(厦门大学化学系厦门361005)关键词:Diclobutrazol,相转移催化,合成,生物活性Diclobutrazol(1)俗名粉锈清,是一种广谱内吸性杀菌剂,... 相似文献
17.
The power dependence of the optical poling process of a new azo chromophore in the polymethylmethacrylate matrix at room temperature has been investigated. The existing theory is found to be inconsistent with the experiment. A simple model based on the rate equation is proposed to describe the writing process of the chromophore/polymer system. The measured growth rate and the plateau second-harmonic generation intensity as induced by all optical poling are found to be in good agreement with the prediction of the simple model. 相似文献
18.
Potential energy functions suitable for the (Cs1–xNaxT2O4)-A type zeolite family were obtained from the known crystal structure of Cs7Na5-A zeolite. Using these potential functions, several other crystal structures in these family were obtained by molecular mechanical calculations. The activation energy - to -cage transmission of the H2 molecule and the void volume of Cs3Na9-A zeolite were calculated. 相似文献
19.
The US National Institute of Standards and Technology (NIST) participated in an international interlaboratory study under
the auspices of the Consultative Committee for Amount of Substance (CCQM) for the determination of 19-norandrosterone (19-NA)
in urine, the principal metabolite of nandrolone and certain other synthetic testosterone substitutes banned for use by the
World Antidoping Agency (WADA). Prior to this study, NIST developed a candidate reference measurement procedure based upon
isotope dilution liquid chromatography/tandem mass spectrometry. This method was applied to a urine sample distributed to
the participants in the study by the Australian National Measurement Institute, Pymble, Australia (NMIA). The NIST results
were in very good agreement with those from the other participants, all of whom used methods based upon gas chromatography/mass
spectrometry. All known significant sources of uncertainty were evaluated, resulting in a relative expanded uncertainty of
less than 5% (coverage factor k = 2). 相似文献
20.
We present a new set of V–V rate coefficients for vibrational levels 0–5 in H2 at 300 K, measured using a stimulated Raman–spontaneous Raman pump/probe apparatus. The measured rate of the non-resonant process, H2(v = 1) + H2(v = 1) → H2(v = 0) + H2(v = 2), is consistent with the previously reported experimental value of Kreutz et al. However, semi-classical predictions of such non-resonant processes, using the identical inter-molecular potential and methodology to that given by Cacciatore and Billing, results in rates which are too slow, by a factor of approximately 3. For the “resonant” V–V process, H2(v = 1) + H2(v = 0) → H2(v = 0) + H2(v = 1), the semi-classical rate is found to be too slow by an even larger factor, of approximately 30, compared to the experimental rate, but consistent with the previously reported experimental result of Farrow and Chandler. Further, unlike the semi-classical model prediction in which the (1, 1 → 2, 0) process rate is predicted to exceed that of the (1, 0 → 0, 1) process, the experimental data shows it to be a factor of approximately 2.5 less, suggesting that semi-classical methods that treat the rotational motion classically are unsuitable for the highly anharmonic H2 molecule. The ratio of pure rotation and rotation–vibration Raman cross sections for scattering from levels 0 and 1 is also determined, with results which agree with calculations of Schwartz and LeRoy, but are somewhat larger than previous experimental results of Cureton. 相似文献