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971.
The presence of an orthopyridyl substituent instead of a p-Tolyl on a chiral sulfoxide group increased drastically the asymmetric induction observed during the addition of arylmethylsulfoxide on carbonyl compounds. 相似文献
972.
Mustayeen A. Khan Denis Cronier Gilles M. Bouet François Vierling 《Transition Metal Chemistry》1995,20(4):369-371
Summary A spectrophotometric study of NiII chloro complexes in the u.v.-vis. region was carried out at 25 °C and constant ionic strength of 1 mol dm–3. A matrix rank treatment method was used to identify two successive mononuclear complexes, NiCl+ and NiCl2, in the three alcohols studied viz. MeOH, EtOH and i-PrOH. The best values for the apparent overall stability constants,
j
, were calculated using a program based on the least-squares method. The log
1 and log
2 values in MeOH, EtOH and i-PrOH are 1.3 and 1.2, 1.7 and 1.8, and 1.9 and 2.2, respectively. The stability increases directly with the mol. wt. of the solvent, or decreases as a linear function of the permittivity of the pure solvent. The electronic spectra and the formation curves of the two complexes in MeOH solutions were calculated. 相似文献
973.
974.
We report the simple and efficient synthesis of 2-arylbenzothiazoles (‘BTA’) and 2-arylbenzoxazoles by direct coupling of benzothiazoles or benzoxazoles with aryl bromides. This method permits direct one-step access to precursors of radiolabeled BTA-1 and BTA-2 and their 6-methoxy analogues, used for in vivo imaging of β-amyloid plaques with positron emission tomography (PET). 相似文献
975.
Jean-Paul Quintard Marie Degueil-Castaing Gilles Dumartin Bernard Barbe Michel Petraud 《Journal of organometallic chemistry》1982,234(1):27-40
The selective deuteration of organotin compounds gives FT 119Sn NMR a new proficiency, since it allows direct access to nJ(SnD) coupling constants. Usually nJ(SnD) is easily apparent for n 1, 2, 3 and sometimes 4 (allyltin compounds). This criterion has been successfully applied for qualitative and subsequently quantitative analysis of vinyltin and allyltin compounds.In the first series, the stereochemistry of alkyne deuterostannation has been easily explored, the assignments of configurations being made directly from 3J(SnD) on the basis of 3J(SnD)trans > 3J(SnD)cis. In the second series, the method appears to be the best tool for simultaneous study of regiochemistry and stereochemistry in the substitution of 3-deutero-5-methyl-2-cyclohexenyl toluene sulphonates by trialkylstannyl anions. The choice between regioisomers was made on the basis of 2J(SnD) >- 4J(SnD).A further aspect of this work is the observation of isotopic effects on 119Sn chemical shifts which were tentatively rationalized considering inductive, steric or hyperconjugative contribution of deuterium. 相似文献
976.
Alvarez-Ibarra C Csákÿ AG Gómez de la Oliva C 《The Journal of organic chemistry》2002,67(9):2789-2797
alpha,beta-Didehydroglutamates have been diastereoselectively transformed into 6-oxoperhydropyridazine-3-carboxylic acid derivatives (OPCAs), which constitute a new class of cyclic amino acid derivatives. Acylation at N-1 renders dipeptides which show considerable conformational rigidity. Semiempirical calculations suggest that OPCAs might force peptide turns with different amplitudes depending on the substitution pattern and relative stereochemistry of the substituents of the pyridazinone ring. 相似文献
977.
Chang‐Yuan Hu Xiao‐Ning Liao Feng‐Yi Li Rong‐Bin Zhang Rong‐Fa Zhang Ting‐Zhi Liu 《中国化学会会志》2007,54(6):1471-1476
Ni‐B and Ni‐B/CNTs amorphous alloy catalysts were prepared by chemical reduction and impregnation‐chemical reduction methods, respectively, and characterized by TEM, ICP, XPS, XRD, BET and CO chemisorption techniques. Their catalytic activities were evaluated in acetylene selective hydrogenation reaction. Based on characterizations, the effects of carbon nanotubes on Ni‐B amorphous alloy were attributed to both its structure effect, dispersing Ni‐B particles, leading to bigger surface area of active nickel and enhancing the thermal stability, and the electronic effect, resulting in electron‐rich nickel centers. Therefore, the superior thermal stability and acetylene selective hydrogenation activities of Ni‐B/CNTs to Ni‐B amorphous catalyst were obtained in the present study. 相似文献
978.
Seven pyrimethanil salts were synthesized by organic base containing nitrogen atom reacting with substituted pyridine acids. They are reported for the first time. Their structures have been confirmed by IR, ^1H NMR and elemental analysis. The preliminary toxicity tests indicated that most of them exhibited excellent fungicidal activities. The relationship between the structures and the fungicidal activities of the compounds was discussed. 相似文献
979.
It is possible to predict the electronic configuration of cations such as Fe(IV), Co(III), and Ni(III) in K2NiF4-type oxides on the base of elementary structural and bonding considerations and to describe the more or less two-dimensional character of the magnetic interactions within the layers containing the 3d ions. 相似文献
980.
The electrochemical method is used in the easy synthesis of donating systems by means of the cathodic reduction of thiopyrones in the presence of alkyl halides. 相似文献