- Amine-chelated aryllithium reagents - Structure and dynamics
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Multinuclear NMR studies of five-membered-ring amine chelated aryllithium reagents 2-lithio-N,N-dimethylbenzylamine (1), the diethylamine and diisopropylamino analogues (2, 3), and the o-methoxy analogue (4), isotopically enriched in 6Li and s
- Reich,Goldenberg,Gudmundsson,Sanders,Kulicke,Simon,Guzei
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- Total synthesis of 13C2,15N-imidacloprid with three stable isotopes in the pyridine ring
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Imidacloprid (IC) is an important crop-protecting insecticide worldwide and commonly used for seed treatment. However, only few data are available on human toxicity of IC. Having in view the metabolic studies at low doses in humans and residue analysis of
- Belov, Vladimir,K?fferlein, Heiko U.
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- Structures of silver nitrate complexes with quinolines according to NMR data
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Silver(I) nitrate complexes [AgNO3(L)2], where L is quinoline or 2-, 4-, and 8-methylquinoline, are synthesized and studied by the multinuclear NMR (1H, 13C, 15N) method in acetonitrile. The influence
- Sakharov,Kovalev,Gorbunova, Yu. E.,Tokmakov,Skabitskii,Kokunov, Yu. V.
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- Synthesis of 15N-labeled vicinal diamines through N-activated chiral aziridines: Tools for the NMR study of platinum-based anticancer compounds
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A new method for the synthesis of 15N-labeled chiral β-diamines from a common precursor, either optically pure amino acids or anti-β-amino alcohols, is reported. The two diastereomeric series of vicinal diamines are produced through the nucleophilic ring opening of activated chiral aziridines. 15N was introduced by means of [ 15N]-benzylamine, prepared from 15NH4Cl. The final compounds are highly valuable because [1H-15N] NMR is considered a powerful tool for studying the chemical properties of platinum-based complexes.
- Berger, Gilles,Gelbcke, Michel,Cau?t, Emilie,Luhmer, Michel,Nève, Jean,Dufrasne, Fran?ois
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supporting information
p. 545 - 548
(2013/02/23)
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- NMR studies on the structure of a lithium amide-chiral diether complex for an asymmetric reaction
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The combination of a chiral diether ligand and a lithium benzyl(trimethylsilyl)amide is a powerful lithium amide reagent for asymmetric conjugate amination of enoate in a toluene solvent. The structure of the chiral diether-lithium amide complex in soluti
- Yamamoto, Yasutomo,Nasu, Hiroyuki,Tomioka, Kiyoshi
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p. 3836 - 3840
(2013/07/05)
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- Enediolate-dilithium amide mixed aggregates in the enantioselective alkylation of arylacetic acids: Structural studies and a stereochemical model
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A combination of X-ray crystallography, 6Li, 15N, and 13C NMR spectroscopies, and density functional theory computations affords insight into the structures and reactivities of intervening aggregates underlying highly selective asymmetric alkylations of carboxylic acid dianions (enediolates) mediated by the dilithium salt of a C2-symmetric chiral tetraamine. Crystallography shows a trilithiated n-butyllithium-dilithiated amide that has dimerized to a hexalithiated form. Spectroscopic studies implicate the non-dimerized trilithiated mixed aggregate. Reaction of the dilithiated amide with the dilithium enediolate derived from phenylacetic acid affords a tetralithio aggregate comprised of the two dianions in solution and the dimerized octalithio form in the solid state. Computational studies shed light on the details of the solution structures and afford a highly predictive stereochemical model.
- Ma, Yun,Stivala, Craig E.,Wright, Ashley M.,Hayton, Trevor,Liang, Jun,Keresztes, Ivan,Lobkovsky, Emil,Collum, David B.,Zakarian, Armen
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p. 16853 - 16864
(2013/12/04)
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- Copper-catalyzed oxidative amidation of aldehydes with amine salts: Synthesis of primary, secondary, and tertiary amides
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A practical method for the amidation of aldehydes with economic ammonium chloride or amine hydrochloride salts has been developed for the synthesis of a wide variety of amides by using inexpensive copper sulfate or copper(I) oxide as a catalyst and aqueous tert-butyl hydroperoxide as an oxidant. This amidation reaction is operationally straightforward and provides primary, secondary, and tertiary amides in good to excellent yields for most cases utilizing inexpensive and readily available reagents under mild conditions. In situ formation of amine salts from free amines extends the substrate scope of the reaction. Chiral amides are also synthesized from their corresponding chiral amines without detectable racemization. The practicality of this amide formation reaction has been demonstrated in an efficient synthesis of the antiarrhythmic drug N-acetylprocainamide.
- Ghosh, Subhash Chandra,Ngiam, Joyce S. Y.,Seayad, Abdul M.,Tuan, Dang Thanh,Chai, Christina L. L.,Chen, Anqi
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p. 8007 - 8015,9
(2012/12/12)
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- Copper-catalyzed oxidative amidation of aldehydes with amine salts: Synthesis of primary, secondary, and tertiary amides
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A practical method for the amidation of aldehydes with economic ammonium chloride or amine hydrochloride salts has been developed for the synthesis of a wide variety of amides by using inexpensive copper sulfate or copper(I) oxide as a catalyst and aqueous tert-butyl hydroperoxide as an oxidant. This amidation reaction is operationally straightforward and provides primary, secondary, and tertiary amides in good to excellent yields for most cases utilizing inexpensive and readily available reagents under mild conditions. In situ formation of amine salts from free amines extends the substrate scope of the reaction. Chiral amides are also synthesized from their corresponding chiral amines without detectable racemization. The practicality of this amide formation reaction has been demonstrated in an efficient synthesis of the antiarrhythmic drug N-acetylprocainamide.
- Ghosh, Subhash Chandra,Ngiam, Joyce S.Y.,Seayad, Abdul M.,Tuan, Dang Thanh,Chai, Christina L.L.,Chen, Anqi
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p. 8007 - 8015
(2013/01/15)
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- 15N double-labeled guanosine from inosine through ring-opening-ring-closing and one-pot Pd-catalyzed C-O and C-N cross-coupling reactions
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(Figure Presented) [N,1-15N2]-Guanosine, or [1,NH2-15N2]-guanosine, and derivatives were prepared from tri-O-acetylinosine, via N-nitration and reaction with 15NH2OH, followed by conversion of the 15N-labeled 1-hydroxyinosine to the corresponding 2,6-dichloropurine riboside. The sequential one-pot C-O and C-N key couplings of this dichloro derivative with PhCH2OH and PhCO15NH2 or iPrCO15NH2 was achieved in good overall yields, with Pd(0)-Xantphos as the best choice of five different catalytic systems examined.
- Caner, Joaquim,Vilarrasa, Jaume
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body text
p. 4880 - 4883
(2010/10/19)
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- Reaction of Ketones with Lithium Hexamethyldisilazide: Competitive Enolizations and 1,2-Additions
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Reaction of 2-methylcyclohexanone with lithium hexamethyldisilazide (LiHMDS, TMS2NLi) displays highly solvent-dependent chemoselectivity. LiHMDS in THF/toluene effect enolization. Rate studies using in situ IR spectroscopy are consistent with a THF concentration-dependent monomer-based pathway. LiHMDS in pyrrolidine/toluene affords exclusively 1,2-addition of the pyrrolidine fragment to form an α-amino alkoxide-LiHMDS mixed dimer shown to be a pair of conformers by using 6Li, 15N, and 13C NMR spectroscopies. Rate studies are consistent with a monomer-based transition structure [(TMS2NLi) (ketone)-(pyrrolidine)3]. The partitioning between enolization and 1,2-addition is kinetically controlled.
- Zhao, Pinjing,Condo, Anthony,Keresztes, Ivan,Collum, David B.
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p. 3113 - 3118
(2007/10/03)
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- Synthesis of L-histidine specifically labelled with stable isotopes
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(2'-13C)-, (1'-15N)- and (3'-15N)-L-Histidine were prepared according to a synthetic scheme that allows the 13C or 15N labelling of all carbon and nitrogen positions or any combination of positions.A 1,5-disubstituted imidazole ring was constructed via condensation of tosylmethyl isocyanide with 3-phenylpropenal and subsequent cycloaddition of benzylamine.The imidazole intermediate was converted into 1-benzyl-5-(chloromethyl)-imidazolium chloride which was coupled to a glycine moiety via an enantioselective coupling with the bislactim ether of cyclo-D-valylglycine.Deprotection of the coupling product afforded L-histidine in high optical purity.Syntheses for the isotopically labelled synthons were developed starting from simple, comercially available, highly enriched compounds.The labelled L-histidines were characterized by mass spectrometry and 1H-, 13C- and 15N-NMR spectroscopy.
- Cappon, J. J.,Witters, K. D.,Baart, J.,Verdegem, P. J. E.,Hoek, A. C.,et al.
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p. 318 - 328
(2007/10/02)
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- Biosynthetic Studies on the Chitinase Inhibitor, Allosamidin. Origin of the Carbon and Nitrogen Atoms.
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Allosamidin 1 is a potent insect chitinase inhibitor produced by Streptomyces sp.The biosynthesis of compound 1 was studied by feeding experiments with labelled precursors.Incorporation experiments using - and D-glucose as well as doubly labelled D-glucosamine revealed that each skeleton of N-acetyl-D-allosamine and allosamizoline 2 was derived grom D-glucosamine.Further experiments with L-arginine and -methionine clarified the origin of the dimethylaminooxazoline moiety of compound 2.
- Zhou, Ze-Yang,Sakuda, Shohei,Yamada, Yasuhiro
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p. 1649 - 1652
(2007/10/02)
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- Effect of Molecular Motion and Solvent Interactions on Nitrogen-15 Relaxation in Anilines
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Dipolar relaxation of 15N in anilines and anilinium ions is influenced by overall motion of the molecule, by rotation about the aryl-nitrogen bond, by inversion of the aniline nitrogen and by interactions of the NH2 or NH3+ group with the solve
- Lambert, Joseph B.,Daniel Stec, III
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p. 301 - 307
(2007/10/02)
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