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排序方式: 共有225条查询结果,搜索用时 41 毫秒
1.
HU Qiao-Sheng HU Chang-MingLaboratory of Organofluorine Chemistry Shanghai Institute of Organic Chemistry Chinese Academy of Sciences Shanghai China 《中国化学》1997,15(3):286-288
Initiated by CrCl3/Fe redox couple, per(poly)fluoroalkyl iodides added to methyl a-acetylamino acrylate, giving B-per(poly)fluoroalkyl a-amino acid derivatives in good yields. 相似文献
2.
Conductance measurements for fifteen uni-univalent salts in 2-methylpyridine-N-oxide (2-MPO) were made over the concentration range of 2–120×10–4 mol-dm–3 at 55°C. All conductance data were evaluated by the Lee-Wheaton equation. The results indicate that all of the salts studied are slightly associated in 2-MPO, which is, nevertheless, a reasonably good ionizing solvent compared to other solvents having a similar value for the dielectric constant. The tetraalkylammonium halides are weaker electrolytes than the tetraphenylborate salts in 2-MPO. Ionic limiting molar conductances were obtained by using as a reference electrolyte tris(iso-pentyl)butylammonium tetraphenylborate. Anions appear to be poorly solvated in this solvent but certain cations, particularly Na+ and K+, show evidence of specific ion-solvent interaction.This study was presented, in part, at the 6th Central Regional Meeting of the American Chemical Society, Detroit, Michigan, April 1974. 相似文献
3.
G. G. Danagulyan D. A. Tadevosyan F. S. Kinoyan 《Chemistry of Heterocyclic Compounds》2006,42(6):782-787
Intermediate recyclization products were obtained in a study of the Kost-Sagitullin rearrangement of a series of 1,2-dialkylpyrimidinium
iodides. The initial attack of the nucleophile leads to the formation of products of the addition of the hydroxyl group, namely,
the corresponding pseudo bases. Heating one of these intermediates in ethanol or in the presence of primary amines leads to
rearrangement to give a pyridone derivative. Upon heating in chloroform, the pseudo bases readily lose a water molecule and
are converted to anhydro bases, namely, derivatives of 1-alkyl-1,2-dihydro-2-methylidenepyrimidine.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 894–900, May, 2006. 相似文献
4.
The addition of gem-difluorinated alkyl iodides to alkynes initiated by AIBN neatly gave the corresponding difluoromethylene vinyl iodides among which the stereoselectivity of aromatic acetylenes was high. The further coupling reaction of E-phenyl difluoromethylene vinyl iodides with terminal alkynes in the presence of catalytic palladium afforded the substituted difluorinated enynes. 相似文献
5.
The transition states of intramolecular 1,4 and 1,5 H-atom transfers, from/to primary (p), secondary (s) or tertiary alkyl (t) and primary (p
a), secondary (s
a) or tertiary (t
a) allyl carbon atoms, have been studied at the level of the semiempirical quantum-chemical method AM1 with the UHF approximation. The activation and reaction enthalpies were calculated and compared with experimental data available in the literature and the calculated data obtained for analogous reactions in alkyl radicals. Correlations were found between the activation enthalpies and the dissociation enthalpies of the bonds broken and formed. 相似文献
6.
Investigation of the LaI2/H2 System: Phase Relations and Stacking Disorder Heating of LaI2 under 1 bar hydrogen pressure to 650 °C leads to light gray LaI2H0.95(3), accompanied by a structural change from tetragonal to hexagonal. Sharp reflections in the XRD pattern can be indexed in P63/mmc with a = 4.2158(7)Å and c = 15.508(3)Å, however, diffuse reflections indicate the presence of stacking faults in the structure, which correspond to a polytypic intergrowth of MoS2 and NbS2 type structural fragments. Increasing the reaction temperature to 730 °C results in a better defined diffraction pattern with the peak positions close to those of the 2H‐NbS2 structure type. An X‐ray powder study of the samples LaI2Hn proved the miscibility gap between LaI2 and LaI2Hn (0 ≤ n ≤ 0.5) in agreement with previous results. With decreasing H‐content of the homogeneous phase the lattice parameters change in opposite direction, a increasing to 4.236(1)Å and c decreasing to 15.39(2)Å for the lower limit. 相似文献
7.
A general synthetic route for the Pd-catalyzed cross-coupling of an arylzinc reagent with arylvinyl iodides (Negishi cross-coupling) has been developed. The system permits efficient and selective preparation of E-stilbenes and their analogues. It also functions effectively at low levels of catalyst loading without the need for an additional ligand and tolerates a wide range of functional groups including heteroaromatic substrates. A systematic study of various parameters was performed and correlated with catalyst-substrate activity. 相似文献
8.
Dr. Lauren E. Longobardi Prof. Alois Fürstner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(43):10063-10068
The hydroboration of internal alkynes with pinacolborane as the reagent catalyzed by [Cp*RuCl]4 results in good to excellent levels of regio- as well as stereoselectivity, provided that the triple bond bears one linear and one singly-branched substituent. In such cases, the reaction follows an unusual trans-addition mode and places the boron entity distal to the branching point. The resulting alkenyl boronates, which are difficult to make otherwise, can be engaged in numerous enabling downstream processes. 相似文献
9.
Hiroya Takada Yoshiaki Nishibayashi Sanjay Kumar Srivastava Kouichi Ohe Sakae Uemura 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):629-632
Asymmetric intramolecular selenocyclisation of alkenoic acids, alkenols and alkenyl urethanes using chiral ferrocenylselenenyl cations proceeds smoothly to give the corresponding lactones, cyclic ethers and N-heterocyclic compounds, respectively, in moderate yields with very high diastereoselectivities. 相似文献
10.
A new copper and silver‐mediated cyanation of aryl iodides with DDQ as a cyanide source is achieved, providing nitriles with good yields. This new approach represents a safe method leading to aryl nitriles. 相似文献