排序方式: 共有15条查询结果,搜索用时 15 毫秒
1.
Arroyo Y Rodríguez JF Santos M Tejedor MA Ruano JL 《The Journal of organic chemistry》2007,72(3):1035-1038
Reactions of (S)-alpha-(methylthio)-2-(p-tolylsulfinyl)benzyl carbanion with different carbonyl compounds proceeds with complete control of the configuration at the benzylic position. Aldehydes yield easily separable mixtures of beta-hydroxy sulfides, epimers at the hydroxylic carbon, where the stereoselectivity depends on steric factors (from 20% to >98% de). 相似文献
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Prof. Dr. Yolanda Arroyo Prof. Dr. M. Ascensión Sanz‐Tejedor Dr. Alejandro Parra Prof. Dr. José Luis García Ruano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(17):5314-5318
Asymmetric nucleophilic monofluoroalkylation of a broad range of aldehydes with an α‐fluoro‐γ‐sulfinylbenzyl carbanion takes place with complete control of the facial selectivity at the carbanion and good to high anti‐diastereoselectivity to give easily separable mixtures of two optically pure 1,2‐fluorohydrin derivatives (up to 24:1 anti/syn). Separation and removal of the p‐tolylsulfinyl group with tBuLi provides enantiomerically pure anti‐1,2‐disubstituted‐1,2‐fluorohydrins, whereas α‐fluorobenzylketones can be obtained by desulfinylation of the mixture followed by pyridinium chlorochromate oxidation (one‐pot process). 相似文献
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Macías FA Galindo JL Varela RM Torres A Molinillo JM Fronczek FR 《Organic letters》2006,8(20):4513-4516
From the medium, polar bioactive fractions of leaf aqueous extract of Helianthus annuus L., heliespirones B (2) and C (3) have been isolated. The structural elucidation was based on extensive spectral studies. A probable biogenesis of heliespirone skeleton is proposed and discussed. The structure of heliespirone B has been confirmed by X-ray diffraction analysis. 相似文献
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Enantiomerically pure syn-1,2-diaryl-1,2-sulfanylamine derivatives can be obtained in a completely stereoselective manner by reaction of the benzylcarbanion Li-(S)-1 with N-phenyl (or PMP)-arylidene aldimines and further desulfinylation with t-BuLi. Theoretical studies at the DFT (mPW1PW91) level with the CPCM model, by using the Gaussian09 program, provide a good explanation for the stereochemical results. 相似文献
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The Ultraviolet Protection Factor of a fabric is a quantitative measurement of the effectiveness of the fabric to protect the human skin against ultraviolet radiation. The protection provided by uncoloured cellulosic fabrics is, in general, too low, but can be improved by the finishing treatment with UV-absorbers. In the present paper cotton fabrics with different compactness, and hence with different initial Ultraviolet Protection Factor values, are treated with several concentrations of an UV-absorber, according to a predefined experimental plan. The influence of each variable as well as their interaction on the response of Ultraviolet Protection Factor is analysed and a statistical model for predictions is proposed. 相似文献
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We characterize the discrete sets Λ⊆ℝ such that {φ(t−λ),λ∈Λ} span L
1(ℝ), φ being an L
1(ℝ)-function whose Fourier transform behaves like e
−2π|ξ|. 相似文献
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Martínez-Palou R Zepeda LG Höpfl H Montoya A Guzmán-Lucero DJ Guzmán J 《Molecular diversity》2005,9(4):361-369
Summary A versatile route to 40-membered library of 2-long alkyl chain substituted benzoazoles (1 and 2) and azole[4,5-b]pyridines (3 and 4) via microwave-assisted combinatorial synthesis was developed. The reactions were carried out in both monomode and multimode microwave
oven. With the latter, all reactions were performed in high-throughput experimental settings consisting of an 8×5 combinatorial
library designed to synthesize 40 compounds. Each step, from the addition of reagents to the recovery of final products, was
automated. The microwave-assisted N-long chain alkylation reactions of 2-alkyl-1H-benzimidazole (1) and 2-alkyl-1H-benzimidazole[4,5-b] pyridines (3) were also studied. 相似文献
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An analytical procedure was developed for the determination of some natural pesticides (piperonyl butoxide, nicotine, rotenone, spinosad, and abamectin B1a) in fruit matrixes. The quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was used for extraction. Analysis of the extract was performed by LC-electrospray ionization (ESI)-MS/MS. The ions prominent in the ESI spectra were [M+Na]+ for abamectin B1a, [M+NH4]+ for piperonyl butoxide, and [M+H]+ for the rest of the compounds. A Zorbax SB-C18 column was used with a programmed gradient mobile phase consisting of (A) water containing 0.1% formic acid and 5 mM ammonium formate, and (B) acetonitrile containing 2 mM sodium acetate. The method was linear within the investigated concentration range, displaying a calibration curve correlation factor of 0.99. The CVs obtained were below 20%, and recoveries were in the 70-110% range. 相似文献
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Ruano JL Parra A Alonso I Fustero S del Pozo C Arroyo Y Sanz-Tejedor A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(22):6142-6147
The preparation of a stabilized monofluorobenzyl carbanion by means of a remote homochiral sulfinyl group and its completely stereoselective reactions with N-p-tolylsulfinylimines are described. The use of these reactions followed by the simultaneous removal of both chiral auxiliaries with tBuLi, which occurs without epimerization at the benzylic position, provides the quickest entry to enantiomerically pure β-fluorinated β-phenylethylamines. 相似文献