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Emmons Reaction (Emmon + reaction)
Selected AbstractsUnexpected Epimerization at C2 in the Horner,Wadsworth,Emmons Reaction of Chiral 2-Substituted-4-oxopiperidines (II).CHEMINFORM, Issue 51 2006Pablo Etayo Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] (E)-Selective Horner,Wadsworth,Emmons Reaction of Aryl Alkyl Ketones with Bis(2,2,2-trifluoroethyl)phosphonacetic Acid.CHEMINFORM, Issue 10 2004Shigeki Sano Abstract For Abstract see ChemInform Abstract in Full Text. [source] Solid-Phase Reactive Chromatography (SPRC): A New Methodology for Wittig and Horner,Emmons Reactions on a Column under Microwave IrradiationEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 2 2010Saada C. Dakdouki Abstract A new methodology named solid-phase reactive chromatography (SPRC), which combines reaction, separation, and purification into a single unit for the preparation of small samples, is described. This method was illustrated in the synthesis of some natural bioactive compounds, namely, methoxylated analogues of resveratrol, alkylresorcinols, and 5-aryl-2,4-pentadienoates, over a column of alumina-KF under microwave irradiation by using the Wittig and Horner,Emmons reactions. This approach permitted the preparation of the target olefins with high purity and good to excellent yields in short reaction times. [source] ChemInform Abstract: Strong Bicyclic Guanidine Base-Promoted Wittig and Horner,Wadsworth,Emmons Reactions.CHEMINFORM, Issue 15 2001Daniele Simoni Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Sequential Double Olefination of 2-(Arylmethylidene)-2-phosphonoacetonitrile with Dimsyl Lithium and Aldehydes: A Domino Route to Densely Substituted 1,3-ButadienesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 22 2008Raghunath Chowdhury Abstract An efficient and highly stereoselective synthesis of densely substituted 1,3-dienes has been achieved which entails a sequential double olefination of 2-(arylmethylidene)-2-phosphonoacetonitriles by a one-pot domino process involving Michael addition of dimsyllithium to 2-(arylmethylidene)-2-phosphonoacetonitrile, Horner,Wadsworth,Emmons reaction of the resulting phosphonate ylide with the added aldehyde followed by base induced methylsulfenoxy elimination. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Asymmetric Synthesis of a Novel Conformationally Constrained D -Lysine Analogue with a Piperidine SkeletonEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2008Pablo Etayo Abstract A practical asymmetric synthesis of enantiomerically pure(2R,4R)-1-(tert -butoxycarbonyl)-4-[2-(methoxycarbonylamino)ethyl]pipecolic acid starting from easily accessible (R)-2-[(S)-1,2-bis(benzyloxy)ethyl]-1-[(S)-1-phenylethyl]-4-piperidone in around 33,% overall yield has been performed. The efficiency of the synthetic strategy developed for the synthesis of this novel conformationally constrained D -lysine analogue relies on the high-yielding Wadsworth,Emmons reaction of a 2-substituted 4-piperidone and the diastereoselective reduction of the exocyclic C=C double bond at the 4-position of the piperidine ring.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Synthesis of Monocyclic and Bicyclic Imino SugarsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2003Markus Kummeter Abstract A diastereoselective aldol reaction between the chelated alanine ester enolate 5 and the protected threose derivative 6, followed by cyclization under Mitsunobu conditions, gave the pipecolinic acid derivative 9. This compound could easily be converted into the versatile protected derivative 11, which could be transformed in excellent yields either into the corresponding piperidine imino sugar 14 or into the unnatural amino acid 17. The imino alcohol 13, an intermediate in the synthesis of imino sugar 14, was also used in a straightforward approach to indolizidinone 19, involving an intramolecular Horner,Emmons reaction for ring-closure. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] First Total Synthesis of Mappain with a Prenylated and Geranylated StilbeneHELVETICA CHIMICA ACTA, Issue 5 2010Lakkoju Chakrapani Abstract The first total synthesis of naturally occurring mappain has been achieved by a convergent sequence. The key strategy involved in the synthesis of mappain was a (E)-stilbene formation by Horner,Wadsworth,Emmons reaction of the corresponding prenylated benzaldehyde with a geranylated benzyl phosphonate. [source] Silver-Catalyzed Aldehyde Olefination Using SiloxyalkynesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2010Jianwei Sun Abstract We describe the development of a silver-catalyzed carbonyl olefination employing electron-rich siloxyalkynes. This process constitutes an efficient synthesis of trisubstituted unsaturated esters, and represents an alternative to the widely utilized Horner,Wadsworth,Emmons reaction. Excellent diastereoselectivities are observed for a range of aldehydes using either 1-siloxy-1-propyne or 1-siloxy-1-hexyne. This mild catalytic process also enables chemoselective olefination of aldehydes in the presence of either ester or ketone functionality. Furthermore, since no by-products are generated, this catalytic process is perfectly suited for development of sequential reactions that can be carried out in a single flask. [source] Synthesis of 18F-labelled stilbenes from 4-[18F]fluorobenz-aldehyde using the Horner,Wadsworth,Emmons reactionJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 2 2007Sven Gester Abstract The first application of the Horner,Wadsworth,Emmons reaction in 18F-chemistry is described. This carbonyl-olefination reaction was performed via a ,multi-step/one-pot' reaction by the coupling of benzylic phosphonic acid esters (3,5-bis-methoxymethoxybenzyl)-phosphonic acid diethyl ester 2e, (4-methoxy-methoxybenzyl)-phosphonic acid diethyl ester 3e and (4-dimethyl-aminobenzyl)phosphonic acid diethyl ester 4d) with 4-[18F]fluorobenzaldehyde to give the corresponding 18F-labelled stilbenes [18F]2g, [18F]3g and [18F]4e exclusively as the expected E -isomers. The radiochemical yields ranged from 9% to 22% (based upon [18F]fluoride, including HPLC purification). The specific activity reached up to 90 GBq/µmol. Copyright © 2007 John Wiley & Sons, Ltd. [source] Enantioselective Synthesis and Cytotoxic Evaluation of 4,5-Dihydro-5-[aryl(hydroxy)methyl]-3-methylidenefuran-2(3H)-onesCHEMISTRY & BIODIVERSITY, Issue 9 2005Tomasz Janecki A series of enantiomerically enriched 4,5-dihydro-5-[aryl(hydroxy)methyl]-3-methylidenefuran-2(3H)-ones (8) were synthesized by means of asymmetric Sharpless dihydroxylation of the 2-phosphorylated 5-aryl-pent-4-enoic acids 13, followed by Horner,Wadsworth,Emmons reaction of the resulting furanones 15 (Scheme,2). An enantiomeric excess (ee) of 20,95% was achieved for compounds 8, and their absolute configurations were determined by the Mosher ester method. Cytotoxic evaluation against L-1210 and HL-60 leukemia cell lines revealed that the target compounds 8 are active in the micromolar concentration range (Table,2). Thereby, significant differences in activity between the corresponding enantiomers were observed for the HL-60 cell line. [source] Solid-Phase Reactive Chromatography (SPRC): A New Methodology for Wittig and Horner,Emmons Reactions on a Column under Microwave IrradiationEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 2 2010Saada C. Dakdouki Abstract A new methodology named solid-phase reactive chromatography (SPRC), which combines reaction, separation, and purification into a single unit for the preparation of small samples, is described. This method was illustrated in the synthesis of some natural bioactive compounds, namely, methoxylated analogues of resveratrol, alkylresorcinols, and 5-aryl-2,4-pentadienoates, over a column of alumina-KF under microwave irradiation by using the Wittig and Horner,Emmons reactions. This approach permitted the preparation of the target olefins with high purity and good to excellent yields in short reaction times. [source] The Interplay of Inverted Redox Potentials and Aromaticity in the Oxidized States of New ,-Electron Donors: 9-(1,3-Dithiol-2-ylidene)fluorene and 9-(1,3-Dithiol-2-ylidene)thioxanthene DerivativesCHEMISTRY - A EUROPEAN JOURNAL, Issue 12 2006Samia Amriou Dr. Abstract Derivatives of 9-(1,3-dithiol-2-ylidene)fluorene (9) and 9-(1,3-dithiol-2-ylidene)thioxanthene (10) have been synthesised using Horner,Wadsworth,Emmons reactions of (1,3-dithiol-2-yl)phosphonate reagents with fluorenone and thioxanthen-9-one. X-ray crystallography, solution electrochemistry, optical spectroscopy, spectroelectrochemistry and simultaneous electrochemistry and electron paramagnetic resonance (SEEPR), combined with theoretical calculations performed at the B3P86/6-31G** level, elucidate the interplay of the electronic and structural properties in these molecules. These compounds are strong two-electron donors, and the oxidation potentials depend on the electronic structure of the oxidised state. Two, single-electron oxidations (<) were observed for 9-(1,3-dithiol-2-ylidene)fluorene systems (9). In contrast, derivatives of 9-(1,3-dithiol-2-ylidene)thioxanthene (10) display the unusual phenomenon of inverted potentials (>) resulting in a single, two-electron oxidation process. The latter is due to the aromatic structure of the thioxanthenium cation (formed on the loss of a second electron), which stabilises the dication state (102+) compared with the radical cation. This contrasts with the nonaromatic structure of the fluorenium cation of system 9. The two-electron oxidation wave in the thioxanthene derivatives is split into two separate one-electron waves in the corresponding sulfoxide and sulfone derivatives 27,29 owing to destabilisation of the dication state. [source] | ||||||||||||||||||||||