共查询到20条相似文献,搜索用时 15 毫秒
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The reaction of (hydroxymethyl)triphenylphosphonium with benzylic or allylic halide under basic conditions at room temperature affords terminal alkenes in 61–89% yields. In this reaction, both formaldehyde and triphenylphosphine are in situ generated from (hydroxymethyl)triphenylphosphonium and further undergo Wittig olefination with benzylic or allylic halide. 相似文献
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Dr. Biswarup Chakraborty Dr. Arseni Kostenko Dr. Prashanth W. Menezes Prof. Dr. Matthias Driess 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(51):11829-11834
An unprecedented one-pot fully electrochemically driven Wittig olefination reaction system without employing a chemical reductant or sacrificial electrode material to regenerate triphenylphosphine (TPP) from triphenylphosphine oxide (TPPO) and base-free in situ formation of Wittig ylides, is reported. Starting from TPPO, the initial step of the phosphoryl P=O bond activation proceeds through alkylation with RX (R=Me, Et; X=OSO2CF3 (OTf)), affording the corresponding [Ph3POR]+X− salts which undergo efficient electroreduction to TPP in the presence of a substoichiometric amount of the Sc(OTf)3 Lewis acid on a Ag-electrode. Subsequent alkylation of TPP affords Ph3PR+ which enables a facile and efficient electrochemical in situ formation of the corresponding Wittig ylide under base-free condition and their direct use for the olefination of various carbonyl compounds. The mechanism and, in particular, the intriguing role of Sc3+ as mediator in the TPPO electroreduction been uncovered by density functional theory calculations. 相似文献
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《中国化学》2018,36(8):723-730
Phosphine‐relayed olefination and aza‐Wittig reactions of readily available aldehydes with 2,2,2‐trifluorodiazoethane (CF3CHN2) have been realized. This protocol enables the facile construction of a series of trifluoromethylated alkenes and hydrazones in good to high yield under mild conditions. 相似文献
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Spino C 《Chemical communications (Cambridge, England)》2011,47(17):4872-4883
Two chiral auxiliaries and the role they play in the preparation of chiral carbonyl compounds and heterocyclic compounds are presented. Key reactions include S(N)2' displacements, Mitsunobu with hydrazoic acid, and 3,3-sigmatropic rearrangements. One of the auxiliaries serves many functions and is removed either by oxidative cleavage or RCM reaction. 相似文献
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A. V. Kuchin S. A. Markova E. V. Gorobets G. A. Tolstikov 《Russian Chemical Bulletin》1990,39(5):1034-1037
A new method of cis-olefination, based on the reaction of aldehydes with geminal alumolithium reagents, is proposed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1151–1154, May, 1990. 相似文献
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E. A. Pakhnutova L. N. Mishenina L. A. Selyunina T. V. Belyaninova Yu. G. Slizhov 《Russian Journal of Applied Chemistry》2018,91(6):899-907
Sol-gel technique was used to develop a method for synthesis of hydrated tricalcium aluminate Ca3[Al(OH)6]2 and surface-layered gas-chromatographic sorbents on its basis. The materials obtained were examined by X-ray diffraction analysis, scanning electron microscopy, X-ray fluorescence microanalysis, adsorption porosimetry, and gas chromatography. It was found that cubic Ca3[Al(OH)6]2 is the main phase in the surface layer of the sorption materials. The Hammett indicator method was used to examine the acid-base properties and the variation of the content of active centers between sorbents obtained in different ways. The chromatographic retention parameters were determined for test compounds, and the polarity and selectivity of the sorbents under study was evaluated. It was shown that Chromaton N-AW modified with hydrated calcium aluminate can be used, with addition of SE-30 stationary liquid phase, to separate complex mixtures of organic compounds. 相似文献
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The Julia-Kocienski olefination provides a versatile platform for the synthesis of fluorovinyl compounds. This review describes our efforts as well as those of others in the synthesis of various fluorinated aryl and heteroaryl sulfones and their utility as olefination reagents for the modular assembly of fluoroalkenes. Where data is available, the influence of the fluorine atom on the reactivity of the olefination reagents and the stereochemical outcome of the olefination are described. 相似文献
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Samir Manna Swagata Paul Wang-Yeuk Kong Debasis Aich Rupam Sahoo Prof. Dean J. Tantillo Prof. Santanu Panda 《Angewandte Chemie (International ed. in English)》2023,62(38):e202309136
Stereoselective Zweifel olefination using boronate complexes carrying two different reactive π-systems was achieved to synthesize vinyl heteroarenes and conjugated 1,3-dienes in good yield and up to 100 % stereoselectivity, which remains unexplored until now. Most importantly, we report the unprecedented formation of E vs. Z-vinyl heteroarenes for different heteroarenes under identical conditions. Density functional theory (DFT) investigations unveil the mechanistic dichotomy between olefin and heteroarene activation followed by 1,2-migration, leading to E or Z-vinyl heteroarenes respectively. We also report a previously unknown reversal of stereoselectivity by using 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as an electrophile. The Zweifel olefination using a boronate complex that carries two different olefins was previously unexplored due to significant challenges associated with the site-selective activation of olefins. We have solved this problem and reported the site-selective activation of olefins for the stereoselective synthesis of 1,3-dienes. 相似文献
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New conditions have been developed for the olefination of diazo compounds catalysed by methyl trioxorhenium. The new system is suitable for unreactive diazo compounds and its utility is demonstrated by the olefination of 3-diazopiperidin-2-one with a range of aromatic, heterocyclic and alkylaldehydes. 相似文献
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A simple, E-stereoselective route for the synthesis of the biologically active compounds trans-pterostilbene and tetramethoxy stilbene from the readily available starting materials 3,5-dimethoxy benzyl alcohol and 4-hydroxy benzaldehyde was developed using Julia olefination as a key reaction. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resources: Full experimental and spectral details.] 相似文献
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Yasuo Nagaoka Hideki Inoue Kiyoshi Tomioka 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6-7):1843-1846
Mono- and di-substituted allenes 5 were synthesized by successive Horner-Wadsworth-Emmons olefination starting from methylene-bisphosphonate 1 and two carbonyl compounds. The key to success is KH or KH-18-crown-6 as a base for the second HWE olefination of hydroxyalkenylphosphonates 4 . 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(3):804-808
A stereodivergent coupling reaction between vinyl halides and boronic esters is described. This coupling process proceeds without a transition‐metal catalyst, instead proceeding by electrophilic selenation or iodination of a vinyl boronate complex followed by stereospecific syn or anti elimination. Chiral, nonracemic boronic esters could be coupled with complete enantiospecificity. The process enables the highly stereoselective synthesis of either the E or Z alkene from a single isomer of a vinyl coupling partner. 相似文献
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Dr. Vikas Tyagi Prof. Dr. Rudi Fasan 《Angewandte Chemie (International ed. in English)》2016,55(7):2512-2516
The olefination of aldehydes constitutes a most valuable and widely adopted strategy for constructing carbon–carbon double bonds in organic chemistry. While various synthetic methods have been made available for this purpose, no biocatalysts are known to mediate this transformation. Reported herein is that engineered myoglobin variants can catalyze the olefination of aldehydes in the presence of α‐diazoesters with high catalytic efficiency (up to 4,900 turnovers) and excellent E diastereoselectivity (92–99.9 % de). This transformation could be applied to the olefination of a variety of substituted benzaldehydes and heteroaromatic aldehydes, also in combination with different alkyl α‐diazoacetate reagents. This work provides a first example of biocatalytic aldehyde olefination and extends the spectrum of synthetically valuable chemical transformations accessible using metalloprotein‐based catalysts. 相似文献
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[formula: see text] The Wittig rearrangements of alpha-alkoxysilanes, promoted by the action of methyllithium were studied. Depending on both the substrate and reaction conditions employed, [2,3]-, [1,2]-, or [1,4]-Wittig rearrangements can be realized. These rearrangements were shown to be initiated by either Si/Li exchange or deprotonation alpha to the silane. Furthermore the sigmatropic shifts can often be followed by other synthetically useful in situ chemical events. 相似文献