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41.
A series of diaryl ketones have been synthesized in good yields (40-78%) through the catalyst-free reaction of trimethylarylstannanes with aroyl chlorides in chlorobenzene as solvent. In addition, an attractive feature is that these reactions are completely regioselective making possible the synthesis of diarylketones which are not usually available under the influence of the directing forces of the substituents present in the aromatic ring. Also, the reaction conditions are mild enough to be applied to acid sensitive molecules. 相似文献
42.
Xinghua Wu 《Tetrahedron letters》2005,46(48):8401-8405
A new method of amide bond formation was developed through the reaction of potassium selenocarboxylates with aromatic azides at room temperature. Potassium selenocarboxylates were prepared in situ by the treatment of diacyl selenides with potassium methoxide at 5 °C under N2. After the addition of azide, the reaction was allowed to gradually warm to room temperature and was stirred for 0.5-2 h. Excellent yields were obtained when electron deficient aromatic azides were used. 相似文献
43.
R. Q. Topper K. Chung C. M. Boelke D. Louie J. S. Kang R. Hannan T. Kiang L. H. Chan 《Theoretical chemistry accounts》2003,109(4):233-238
2-(Acetylamino)fluorene (AAF), a potent mutagen and a prototypical example of the mutagenic aromatic amines, forms covalent
adducts to DNA after metabolic activation in the liver. A benchmark study of AAF is presented using a number of the most widely
used molecular mechanics and semiempirical computational methods and models. The results are compared to higher-level quantum
calculations and to experimentally obtained crystal structures. Hydrogen bonding between AAF molecules in the crystal phase
complicates the direct comparison of gas-phase theoretical calculations with experiment, so Hartree–Fock (HF) and Becke–Perdew
(BP) density functional theory (DFT) calculations are used as benchmarks for the semiempirical and molecular mechanics results.
Systematic conformer searches and dihedral energy landscapes were carried out for AAF using the SYBYL and MMFF94 molecular
mechanics force fields; the AM1, PM3 and MNDO semiempirical quantum mechanics methods; HF using the 3-21G*and 6-31G* basis
sets; and DFT using the nonlocal BP functional and double numerical polarization basis sets. MMFF94, AM1, HF and DFT calculations
all predict the same planar structures, whereas SYBYL, MNDO and PM3 all predict various nonplanar geometries. The AM1 energy
landscape is in substantial agreement with HF and DFT predictions; MMFF94 is qualitatively similar to HF and DFT; and the
MNDO, PM3 and SYBYL results are qualitatively different from the HF and DFT results and from each other. These results are
attributed to deficiencies in MNDO, PM3 and SYBYL. The MNDO, PM3 and SYBYL models may be unreliable for compounds in which
an amide group is immediately adjacent to an aromatic ring.
Received: 26 May 2002 / Accepted: 12 December 2002 /
Published online: 14 February 2003 相似文献
44.
利用电动势法得到了牛血清白蛋白(BSA)与十二烷基硫酸钠(SDS)相互作用的结合等温线. 通过四阶导数紫外光谱法和荧光光谱法研究了相互作用过程中芳香族氨基酸残基微环境极性的变化. 通过研究发现, 随着SDS浓度的逐渐增大, SDS在BSA上的平均结合数(v)逐渐增大, 色氨酸(Trp)残基所处微环境的极性在减弱后保持基本不变, 酪氨酸残基所处微环境的极性在明显增强后稍有减弱, 苯丙氨酸残基所处微环境的极性略有增强. 结果表明, 当v由0增大到14时, SDS主要结合在BSA的Trp-213附近并逐渐形成聚集体, 从而诱导BSA由结构域ⅡA 开始逐渐展开. 此后, SDS呈正协同作用的特点与BSA 结合, v急剧增大. 当v约为302 时, SDS在BSA上的结合基本达到饱和, BSA的构象趋于稳定. 相似文献
45.
Marta Catellani Sara Deledda Françoise Hénin Jacques Muzart 《Journal of organometallic chemistry》2003,687(2):473-482
A novel reaction sequence leading to the synthesis of substituted biphenyls containing a carbonyl group in an aliphatic chain has been achieved in one-pot reaction starting from iodoarenes and allylic alcohols under the catalytic action of palladium and norbornene. The latter is temporarily incorporated into a palladacycle, which directs the reaction towards the selective formation of an arylaryl bond. Norbornene spontaneously deinserts to allow the biphenylylpalladium bond thus formed to react in its turn with the allylic alcohol. 相似文献
46.
利用电动势法得到了牛血清白蛋白(BSA)与十二烷基硫酸钠(SDS)相互作用的结合等温线. 通过四阶导数紫外光谱法和荧光光谱法研究了相互作用过程中芳香族氨基酸残基微环境极性的变化. 通过研究发现, 随着SDS浓度的逐渐增大, SDS在BSA上的平均结合数(v)逐渐增大, 色氨酸(Trp)残基所处微环境的极性在减弱后保持基本不变, 酪氨酸残基所处微环境的极性在明显增强后稍有减弱, 苯丙氨酸残基所处微环境的极性略有增强. 结果表明, 当v由0增大到14时, SDS主要结合在BSA的Trp-213附近并逐渐形成聚集体, 从而诱导BSA由结构域ⅡA 开始逐渐展开. 此后, SDS呈正协同作用的特点与BSA 结合, v急剧增大. 当v约为302 时, SDS在BSA上的结合基本达到饱和, BSA的构象趋于稳定. 相似文献
47.
“Aromatic nucleophilic substitution-rearrangement (SNAr-rearrangement)” mechanism provided a powerful tool to design fluorescent probes for the discrimination between biothiols. 相似文献
48.
Xu-Ni Cao Jin-Hua Li Hai-Hong Xu Jia-Rong Zhan Li Lin Katsunobu Yamamoto Li-Tong Jin 《Chromatographia》2004,59(3-4):167-172
Liquid chromatography with amperometric detection (LC-AD) is developed and applied to simultaneously determine five aromatic amines. In the LC-AD, a new carbon nanotubes/poly(3-methylthiophene) modified dual-electrode is fabricated and then used as the working electrode. It is found that this chemically modified electrode (CME) exhibits efficiently electrocatalytic oxidation for aromatic amines with relatively high sensitivity, stability and long-life. Thus, lower detection in LC-AD can be achieved, which are 4.0 × 10–8 mol L–1 for aniline, 1.6 ×10–7 mol L–1 for 4-nitroaniline, 1.0 × 10–7 mol L–1 for 4-chloroaniline, 1.5 × 10–7 mol L–1 for 1-naphthylamine, 1.7 × 10–7 mol L–1 for 2-bromoaniline. The recoveries of the five analytes are also determined, which range between 0.95 and 1.05 for drinking water, 0.86 and 1.10 for the LiWa River water. 相似文献
49.
New optically active polyamides were synthesized according to two ways: using a microwave-assisted polycondensation of an optically active isosorbide-derived diacylchloride with different aromatic diamines in NMP and using interfacial polymerization from an isosorbide-derived diamine with different diacylchlorides. The polymers are obtained with inherent viscosities in the range from 0.11 to 1.05 dL/g. The DSC and TGA measurements clearly demonstrate the high thermal stability of these polymers when considering the range of the melting points from 200 °C to 300 °C and the absence of decomposition till 350 °C. 相似文献
50.
Palladium-benzimidazolium salt catalyst systems have been studied for the Suzuki coupling. A different substitutent effect has been uncovered with respect to nitrogen substituents in the benzimidazolium salts from the palladium-imidazolium salt analogs. A practical and highly active palladium catalyst system, PdCl2/N,N′-dibenzylbenzimidazolium chloride 2, has been identified for the Suzuki coupling of aromatic halides with arylboronic acids. The coupling of a wide array of aromatic halides with arylboronic acids with the PdCl2-2 catalyst system gave good to excellent yields. The effective palladium loading could be as low as 0.0001 mol% and 0.01-0.1 mol% for iodide and bromide substrates, respectively. The coupling of unactivated aromatic chlorides with arylboronic acids also gave good results using Cs2CO3 as base with a 2 mol% palladium loading. The electronic factors from aromatic halides exert a significant influence on the Suzuki coupling catalyzed by the PdCl2-2 system while the electronic effect from the arylboronic counterparts is negligible. The aromatic halides with modest steric hindrance could also couple smoothly with phenylboronic acids using the PdCl2-2 catalyst system. 相似文献