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排序方式: 共有317条查询结果,搜索用时 19 毫秒
311.
Saadi Bayat Bimo A. Tejo Emilia Abdulmalek Normi Mohd Yahya Abu Bakar Salleh 《合成通讯》2013,43(20):2725-2732
This work reports the effectiveness of short polar peptides as asymmetric catalysts in Michael reactions to attain good yields of enantio- and diastereoselective isomers. In a comparison, glutamic acid and histidine produced greater ee and yields when they were applied as the second amino acid in short trimeric peptides. These short polar peptides were found to be efficient organocatalysts for the asymmetric Michael addition reaction in water.
Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file. 相似文献
312.
Rahim Hekmatshoar Sodeh Sadjadi Samaheh Sadjadi Majid M. Heravi Yahya S. Beheshtiha Fatemeh F. Bamoharram 《合成通讯》2013,43(11):1708-1716
An efficient synthetic method of six- and five-member nitrogen heterocyclic compounds was developed. Nitrogen heterocyclic compounds were prepared by condensation of the β-dicarbonyl compounds with the corresponding β- or γ-amino alcohols, subsequent cyclization, and spontaneous aromatization in the presence of a catalytic amount of Keggin-type heteropoly acids under very mild conditions. 相似文献
313.
Majid M. Heravi Yahya S. Beheshtiha Zahra Pirnia Samaheh Sadjadi Mina Adibi 《合成通讯》2013,43(20):3663-3667
4H-Pyrans are synthesized through one-pot, three-component reaction of benzaldehyde, malononitrile, and ethyl acetoacetate using Cu(II) oxymetasilicate as an efficient, reusable catalyst. The procedure offers advantages in terms of better yields, short reaction times, mild reaction conditions, and reusability of the catalyst. 相似文献
314.
Rahim Hekmatshoar Ghodsieh Nanva Kenary Sodeh Sadjadi Yahya S. Beheshtiha 《合成通讯》2013,43(13):2007-2013
An efficient method for the synthesis of 4-amino-5-pyrimidinecarbonitriles by three-component reaction of malononitrile, aldehydes, and N-unsubstituted amidines, under aqueous conditions, using ZnO nanoparticles as catalyst is reported. The catalyst exhibited remarkable activity and is recyclable. 相似文献
315.
Ultrasonic assisted extraction-dispersive liquid-liquid microextraction (UAE-DLLME) coupled with gas chromatography (GC) was applied for extraction and determination of essential oil constituents of the plant Oliveria decumbens Vent. Scanning electron microscopy (SEM) was used to see the effect of ultrasonic radiation on the extraction efficiency. By comparison with hydrodistillation, UAE-DLLME is fast, low cost, simple, efficient and consuming small amount of plant materials (~1.0 g). The effects of various parameters such as temperature, ultrasonication time, volume of disperser and extraction solvents were investigated by a full factorial design to identify significant variables and their interactions. The results demonstrated that temperature and ultrasonication time had no considerable effect on the results. In the next step, a central composite design (CCD) was performed to obtain the optimum levels of significant parameters. The obtained optimal conditions were: 0.45 mL for disperser solvent (acetonitrile) and 94.84 μL for extraction solvent (chlorobenzene). The limits of detection (LODs), linear dynamic range and determination coefficients (R(2)) were 0.2-29 ng mL(-1), 1-2100 ng mL(-1) and 0.995-0.998, respectively. The main components of the essential oil were: thymol (47.06%), carvacrol (23.31%), gamma-terpinene (18.94%), p-cymene (8.71%), limonene (0.76%) and myristicin (0.63%). 相似文献
316.
C. Naceur Abouloula M. Rizwan V. Selvanathan C. I. Abdullah A. Hassan R. Yahya A. Oueriagli 《Ionics》2018,24(12):3827-3836
Biopolymer-based materials from renewable sources are the core target of the researchers in modern time. Following this motivation, we have developed solid polymer electrolytes (SPEs) from empty fruit branch (EFB) of oil palm. The cellulose was extracted from EFB and modified to carboxymethyl cellulose (CMC) by its reaction with monochloroacetic acid in a strongly alkaline medium. The samples were characterized by FTIR, 13C NMR, and XRD to confirm the presence of different functional groups, new connectivity, and crystalline/amorphous nature of the materials, respectively. The CMC-based SPEs were fabricated by blending it with different quantities of lithium iodide (LiI) as dopant. The existence of polymer-salt interactions was revealed by FTIR analysis. The maximum ionic conductivity of 5.58?×?10?3 S cm?1 was observed on sample containing 65 wt% LiI with the lowest activation energy of 0.249 eV. 相似文献
317.
The electronic absorption spectra as well as molecular orbital (MO) calculations at the ab initio level of some 1,2‐benzoquinone diazides have been studied. The results of spectral study support the open isomer over the closed one (1,2,3‐oxadiazole derivative) and indicate the contribution of both the benzenoid and quinonoid structures to the molecule. Spectral results were confirmed by MO calculations. The results of the latter gave a lower total energy for a benzoquinone diazide than for 1,2,3‐benzoxadiazole structure. Bond length and charge density indicate the contribution of both quinonoid and benzenoid structures for the studied compounds. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 78: 52–62, 2000 相似文献