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排序方式: 共有548条查询结果,搜索用时 15 毫秒
1.
Li‐Na Wang Zhen‐Xun Zhou Dr. Xiao‐Na Li Dr. Tong‐Mei Ma Prof. Sheng‐Gui He 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(18):6957-6961
In addition to generation of a methyl radical, formation of a formaldehyde molecule was observed in the thermal reaction of methane with AuNbO3+ heteronuclear oxide cluster cations. The clusters were prepared by laser ablation and mass‐selected to react with CH4 in an ion‐trap reactor under thermal collision conditions. The reaction was studied by mass spectrometry and DFT calculations. The latter indicated that the gold atom promotes formaldehyde formation through transformation of an Au?O bond into an Au?Nb bond during the reaction. 相似文献
2.
Martien A. Würdemann Cristina Niţu Dr. Stefaan M. A. De Wildeman Dr. Katrien V. Bernaerts Prof. Dr. Romano V. A. Orru 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(36):8090-8100
Pyrazines are an underreported class of N-heterocycles available from nitrogen-rich biomass presenting an interesting functional alternative for current aromatics. In this work, access to pyrazines obtained from amino acids by using the 90 year old Dakin–West reaction was explored. After a qualitative screening several functional proteinogenic amino acids proved good substrates for this reaction, which were successfully scaled to multigram scale synthesis of the corresponding intermediate α-acetamido ketones. Subsequently, the conditions towards pyrazine formation using δ-amino-levulinic acid were optimized, and these were employed to synthesize a relevant set of five functional dimethylpyrazines in high purity. These pyrazines can be considered a versatile toolbox of aromatic building blocks for a wide range of applications, such as in the synthesis of polymers or metal–organic frameworks. 相似文献
3.
Balasubramanian Sridhar Jagadeesh Babu Nanubolu Krishnan Ravikumar 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(2):128-135
A new polymorph of cytosine, C4H5N3O, is reported half a century after the report of its first known crystal structure [Barker & Marsh (1964). Acta Cryst. 17 , 1581–1587]. Cytosine thus provides the first polymorphic example in the category of parent nucleobases. The new form, denoted (Ib), was observed unexpectedly during an attempt to cocrystallize cytosine with catechol. Form (Ib) crystallizes in the orthorhombic centrosymmetric space group Pccn with two molecules in the asymmetric unit. The previously known form, denoted (Ia), crystallizes in the orthorhombic noncentrosymmetric space group P212121. The cytosine molecule is planar in both forms. Hydrogen‐bonding interactions are also similar for both forms. Infinite one‐dimensional ribbons composed of cytosine base‐pair dimers in R22(8) arrangements are observed in both (Ia) and (Ib). However, the way that the ribbons are packed differs in (Ia) and (Ib). This appears to guide the centrosymmetric versus noncentrosymmetric space‐group selection through the formation of an inversion‐related motif in polymorph (Ib) and a helical propagation in polymorph (Ia). A few selected polymorphic systems have been gathered from the Cambridge Structural Database to understand possible structural features responsible for achiral molecules adopting centro‐ and noncentrosymmetric space groups. 相似文献
4.
Oleksandr P. Demchuk Bohdan V. Bobovskyi Bohdan V. Vashchenko Dr. Oleksandr V. Hryshchuk Artem Skreminskyi Dr. Anton V. Chernykh Dr. Viktoriia S. Moskvina Dr. Olga V. Hordiyenko Prof. Dr. Dmitriy M. Volochnyuk Prof. Dr. Oleksandr O. Grygorenko 《European journal of organic chemistry》2023,26(24):e202300292
Synthesis and physicochemical characterization of all possible cis- and trans-1,3-disubstituted cyclobutane-derived amines and carboxylic acids bearing mono-, di- and trifluoromethyl groups at the C-3 position is disclosed. Tetramethylammonium fluoride (TMAF)- or morpholinosulfur trifluoride (Morph-DAST)-mediated nucleophilic fluorination of appropriate cis- and trans-diastereomeric substrates was used as the key step for the preparation of CH2F- and CHF2-substituted derivatives. To obtain the corresponding cis- and trans-isomeric CF3-substituted derivatives, resolution of known 3-(trifluoromethyl)cyclobutanecarboxylic acid (obtained as a mixture of diastereomers) was applied. The proposed procedures were suitable for the preparation of corresponding fluoroalkyl-substituted cyclobutane-derived amines and carboxylic acids on up to 50 g scale. All 12 building blocks obtained were characterized by measuring dissociation constants (pKa) and lipophilicities (LogP, for model derivatives) to evaluate the effect of the fluoroalkyl substituents on their physicochemical properties relevant to further drug discovery applications. 相似文献
5.
Dmytro I. Sierov Illia V. Dzhulai Kateryna I. Siryk Kostiantyn V. Shvydenko Tetiana I. Shvydenko Prof. Dr. Kostiantyn Nazarenko Prof. Dr. Aleksandr Kostyuk Oleksandr S. Liashuk Prof. Dr. Oleksandr O. Grygorenko 《European journal of organic chemistry》2023,26(34):e202300538
A systematic study on the SnAr reaction of halogenated fluoropyridines and (hetero)aliphatic nitrile anions as an approach to the synthesis of functionalized pyridines bearing a (cyclo)alkyl or saturated heterocyclic substituent by is described. The scope of the method was demonstrated on a wide range of (hetero)aliphatic nitriles (including three- to six-membered cycloalkane derivatives and N-, O-, S-containing saturated heterocycles) and all isomeric halogenated 2-and 4-fluoropyridines. High chemo- and regioselectivity (i. e., exclusive substitution of the fluorine atom), as well as excellent scalability of the proposed reaction sequence were demonstrated (up to 450 g for the arylation step or up to 77 g of cycloalkylpyridine over two steps in a single run). The utility of the synthesized products was illustrated in the additional functional group transformations resulting in synthetically valuable pyridine-containing building blocks. 相似文献
6.
Xiaoxuan Han Ruijie Zhao Yong Tian Yutong Li Xu-Wei Chen Jiping Ma Weiliang Wang Yanfeng Zhang Song Geng Menglin Liu 《Journal of separation science》2023,46(11):2300006
A high-performance liquid chromatography-ultraviolet method was developed for rapidly and simultaneously analyzing novel and typical bisphenols in building materials, including bisphenol S, diphenolic acid, bisphenol F, bisphenol E, bisphenol A, bisphenol B, bisphenol AF, bisphenol AP, bisphenol C, bisphenol FL, bisphenol Z, bisphenol BP, bisphenol M, and bisphenol P. By using a Kromasil 100–5 C18 column, these bisphenols were completely separated in 40 min via gradually increasing the concentration of methanol in the mobile phase from 45 to 80% during the elution process. In particular, this method achieved the synchronous analysis of bisphenol S, diphenolic acid, bisphenol FL, bisphenol BP, and bisphenol M through HPLC, which were difficult to separate and had to be identified and detected through mass spectrometry. The limits of detection of the method ranged from 0.002 to 0.040 mg/L for these 14 bisphenols, with a precision of less than 4.9% (n = 7, c = 0.05 mg/L). The analytical results for five types of building materials (phenolic, epoxy, polycarbonate, polyester, and polysulfone resins) indicated that the proposed method is appropriated for the rapid measurement of bisphenols in real samples. 相似文献
7.
Dr. Joost Steverlynck Dr. Ruzal Sitdikov Prof. Dr. Magnus Rueping 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(46):11751-11772
In the field of medicinal chemistry, the precise installation of a trideuteromethyl group is gaining ever-increasing attention. Site-selective incorporation of the deuterated “magic methyl” group can provide profound pharmacological benefits and can be considered an important tool for drug optimization and development. This review provides a structured overview, according to trideuteromethylation reagent, of currently established methods for site-selective trideuteromethylation of carbon atoms. In addition to CD3, the selective introduction of CD2H and CDH2 groups is also considered. For all methods, the corresponding mechanism and scope are discussed whenever reported. As such, this review can be a starting point for synthetic chemists to further advance trideuteromethylation methodologies. At the same time, this review aims to be a guide for medicinal chemists, offering them the available C−CD3 formation strategies for the preparation of new or modified drugs. 相似文献
8.
9.
地下厂房位置及轴线方向的选择是一项重要的地质工作,本文在分析琅山抽水蓄能电站厂房区工程地质条件的基础上,就厂房位置及其轴线方向的优化选择,进行了分析和研究。 相似文献
10.
Most previous investigations on interference effects of tall buildings under wind actions focused on the wind induced interference effects between two buildings,and the interference effects of three or more buildings have seldom been studied so far due to the huge workload involved in experiments and data processing.In this paper,mean and dynamic force/response interference effects and peak wind pressure interference effects of two and three tall buildings,especially the three-building configuration,are investigated through a series of wind tunnel tests on typical tall building models using high frequency force balance technique and wind pressure measurements.Furthermore,the present paper focuses on the effects of parameters,including breadth ratio and height ratio of the buildings and terrain category,on the interference factors and derives relevant regression results for the interference factors. 相似文献