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排序方式: 共有268条查询结果,搜索用时 31 毫秒
21.
The first asymmetric synthesis of α,β-disubstituted γ-phosphono sulfonates is reported. The key step is the Michael addition of a lithiated enantiopure sulfonate bearing an inexpensive chiral sugar auxiliary to α,β-unsaturated phosphonates in good diastereoselectivities. After chromatographic purification, the cleavage of the chiral sugar auxiliary proceeds without any epimerization or racemization to form the corresponding isopropyl sulfonate in very good overall yield (75%) and excellent diastereomeric and enantiomeric excess (de, ee ? 95%). 相似文献
22.
Firouz Matloubi Moghaddam Mostafa Kiamehr Salman Taheri Zohreh Mirjafary 《Helvetica chimica acta》2010,93(5):964-973
An efficient synthesis of polycyclic indole derivatives is achieved via domino Knoevenagel–hetero‐Diels–Alder reaction of O‐acrylated salicylaldehyde derivatives with dihydroindole‐2‐thiones in H2O as solvent. The products are formed in good‐to‐excellent yields with high regio‐ and stereoselectivity. 相似文献
23.
The synthesis of a series of benzoxazocines has been achieved in good yields by tandem C-alkylation and intramolecular O-alkylation of 1,3-dicarbonyl compounds with quinolinium salts. This is a novel example of the synthesis of eight-membered rings via a tandem process, which provides a method for the synthesis of medium-ring heterocycles. 相似文献
24.
Saman Azodi-Deilami Majid Abdouss Seyed Alireza Hasani 《Central European Journal of Chemistry》2010,8(4):861-869
In this paper, a highly selective molecularly imprinted polymer (MIP) for tramadol hydrochloride, a drug used to treat moderate
to severe pain, was prepared and its use as solid-phase extraction (SPE) sorbent was demonstrated. The molecularly imprinted
solid-phase extraction procedure followed by high performance liquid chromatography with ultraviolet detector (MISPE-HPLC)
was developed for selective extraction and determination of tramadol in human plasma and urine. The optimal conditions for
molecularly imprinted solid-phase extraction (MISPE) consisted of conditioning with 1 mL methanol and 1 mL of deionized water
at neutral pH, loading of tramadol sample (50 μg L−1) at pH 7.5, washing using 1 mL acetone and elution with 3 × 1 mL of 10% (v/v) acetic acid in methanol. The MIP selectivity
was evaluated by checking several substances with similar molecular structures to that of tramadol. Results from the HPLC
analyses showed that the calibration curve of tramadol (using MIP from human plasma and urine) is linear in the ranges of
6–100 and 3–120 μg L−1 with good precisions (1.9% and 2.9% for 5.0 μg L−1), respectively. The recoveries for plasma and urine samples were higher than 81%.
相似文献
25.
K. Ahmadi F. Hasani B. Kheirfam 《Journal of Mathematical Modelling and Algorithms》2014,13(2):191-208
We present a full-Newton step primal-dual infeasible interior-point algorithm based on Darvay’s search directions. These directions are obtained by an equivalent algebraic transformation of the centering equation. The algorithm decreases the duality gap and the feasibility residuals at the same rate. During this algorithm we construct strictly feasible iterates for a sequence of perturbations of the given problem and its dual problem. Each main iteration of the algorithm consists of a feasibility step and some centering steps. The starting point in the first iteration of the algorithm depends on a positive number ξ and it is strictly feasible for a perturbed pair, and feasibility steps find strictly feasible iterate for the next perturbed pair. By using centering steps for the new perturbed pair, we obtain strictly feasible iterate close to the central path of the new perturbed pair. The algorithm finds an ?-optimal solution or detects infeasibility of the given problem. The iteration bound coincides with the best known iteration bound for linear optimization problems. 相似文献
26.
Manuel M. Bentlohner Wilhelm Klein Zohreh H. Fard Laura‐Alice Jantke Thomas F. Fssler 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(12):3819-3824
The accessibility of triads with deltahedral Zintl clusters in analogy to fullerene–linker–fullerene triads is another example for the close relationship between fullerenes and Zintl clusters. The compound {[K(2.2.2‐crypt)]4[RGe9‐CHCH CHCH‐Ge9R]}(toluene)2 (R=(2Z,4E)‐7‐amino‐5‐aza‐hepta‐2,4‐dien‐2‐yl), containing two deltahedral [Ge9] clusters linked by a conjugated (1Z,3Z)‐buta‐1,3‐dien‐1,4‐diyl bridge, was synthesized through the reaction of 1,4‐bis(trimethylsilyl)butadiyne with K4Ge9 in ethylenediamine and crystallized after the addition of 2.2.2‐cryptand and toluene. The compound was characterized by single‐crystal structure analysis as well asNMR and IR spectroscopy. 相似文献
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29.
Sulfonyl Ketenimines as Key Intermediates in One‐Pot Synthesis of N‐Sulfonyl‐2‐alkaneimidoyl Selenocyanates
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Sulfonyl‐ketenimine intermediates, generated by the addition of Cu acetylides to sulfonyl azides, are trapped by KSeCN to afford N‐sulfonyl‐2‐alkaneimidoyl selenocyanates in moderate‐to‐good yields. 相似文献
30.
Zohreh Rashidi RanjbarAli Morsali 《Polyhedron》2011,30(6):929-934
A nano-sized mixed-ligand Cd(II) coordination polymer, {[Cd(bpa)(4,4′-bipy)2(H2O)2](ClO4)2}n (1); bpa = trans-1,2-bis(4-pyridyl)ethane and 4,4′-bipy = 4,4′-bipyridine, has been synthesized by a sonochemical method and characterized by IR and 1H NMR spectroscopy. Compound 1 grows in one dimension by two different bridging ligands, 4,4′-bipy and bpa. The thermal stability of compound 1 in the bulk form and nano-sized was studied by thermogravimetric (TG) and differential thermal analysis (DTA). The crystallinity of this compound was studied by X-ray powder diffraction and compared with an XRD simulation of the single crystal data. CdO nanoparticles were obtained by direct calcination at 500 °C and decomposition in oleic acid at 200 °C of the nano-sized compound 1. The obtained cadmium(II) oxide nano-particles were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). 相似文献