Identification des configurations relatives d'alcools secondaires α-cyclopropylidéniques et α-vinylcyclopropaniques. Attribution de structure aux éthyl-6 diméthyl-2,4 oxa-3 bicyclo [3.1.01,5]hexanes

1979 ◽  
Vol 57 (17) ◽  
pp. 2314-2320 ◽  
Author(s):  
Maurice Vincens ◽  
Claude Dumont ◽  
Michel Vidal
Keyword(s):  
Basic Medium ◽  
Secondary Alcohols ◽  
Nmr Studies ◽  
Derivatives Of ◽  
C Nmr

During a stereochemical study of α-cyclic secondary alcohols, the relative configurations of the E, R*, and S* isomers of 1-(2-ethyl-3-ethylidene(1R*,2R*)cyclopropyl)ethanol was determined. Treatment in a basic medium of these secondary diastereomeric alcohols leads to the R* and S* isomers of 1-(2-ethyl-3-vinyl(1R*,2S*,3S*)cyclopropyl)ethanol. Cyclic oxymercuration of these cyclopropanoic derivatives yields the di-endo, di-exo, and exo–endo derivatives of 6-ethyl-2,4-dimethyl-3-oxabicyclo[3.1.0.1,5]hexane. The determination of the structure as bicyclic ethers, based on ir and 1H and 13C nmr studies, permits the assignment of the relative configurations of the vinylcyclopropanoic and cyclopropylidene alcohols. [Journal translation]

scholarly journals The First Liquid-Chromatographic Separation of the (R)- and (S)-Enantiomers of a Chiral Silanol, Silane and Germane

1995 ◽  
Vol 50 (4) ◽  
pp. 568-572 ◽  
Author(s):  
Reinhold Tacke ◽  
Dirk Reichel ◽  
Kurt Günther ◽  
Stefan Merget
Keyword(s):  
Chiral Stationary Phase ◽  
Enantiomeric Purity ◽  
Nmr Studies ◽  
Enantiomerically Pure ◽  
Chemically Modified ◽  
Liquid Chromatographic Separation ◽  
Racemic Mixtures ◽  
Liquid Chromatographic ◽  
C Nmr

The racemic mixtures of the muscarinic antagonists cyclohexyl(phenyl)(2-pyrrolidinoethyl)silanol (sila-procyclidine, rac-1), cyclohexyl(hydroxymethyl)phenyl(2-piperidinoethyl)-silane (rac-2) and cyclohexyl(hydroxymethyl)phenyl(2-piperidinoethyl)germane (rac-3) were resolved by analytical liquid chromatography (HPLC) using chemically modified cellulose (1) or amylose (2, 3) as the chiral stationary phase. This chromatographic method was used for the quantitative determination of enantiomeric purity of the (R)- and (S)-enantiomers of 1 - 3 , which were obtained by preparative resolution with chiral auxiliary agents. Furthermore, the enantiomeric purity of these samples was established by 13C NMR studies using chiral shift reagents. According to these studies, the resolved antipodes of 1 - 3 (obtained by preparative resolution) were almost enantiomerically pure [HPLC: ≥ 98.2% ee ((R )-3) to 99.4% ee ((R)-1, (S)-1); NMR: ≥ 97% ee].

Tricarbonylferrole iron tricarbonyl derivatives: formation from thiophenes and iron atoms in a CO atmosphere and fluxional behaviour

1977 ◽  
Vol 55 (20) ◽  
pp. 3509-3514 ◽  
Author(s):  
Tristram Chivers ◽  
Peter L. Timms
Keyword(s):  
Nmr Studies ◽  
Warm Up ◽  
Metal Atoms ◽  
Iron Tricarbonyl ◽  
Derivatives Of ◽  
C Nmr

Co-condensation of metal atoms (Cr, Fe) with thiophenes [Formula: see text] (R = R′ = H, Me; R = H, R' = Me) at −196 °C leads to desulphurization of the thiophene. Warm-up of the iron–thiophene co-condensate in a CO atmosphere produces derivatives of tricarbonylferrole iron tricarbonyl, C4H2RR′Fe2(CO)6. 13C nmr studies of these complexes show that the tricarbonyl ferrole unit is static from −95 °C to +60 °C, while the π-Fe(CO)3 group exhibits fluxional behaviour. Addition of dienes or Me3P in hexane to the iron–thiophene co-condensate at −196 °C yields thermally unstable red solutions on melting.

Seven-coordinate metal carbonyl derivatives of cis-(CH3)2AsC(CF3)=C(CF3)As(CH3)2

1976 ◽  
Vol 54 (16) ◽  
pp. 2548-2556 ◽  
Author(s):  
William R. Cullen ◽  
Lynn M. Mihichuk
Keyword(s):  
Metal Carbonyl ◽  
Activation Parameters ◽  
Nmr Studies ◽  
H Nmr ◽  
Carbonyl Derivatives ◽  
Derivatives Of ◽  
C Nmr

The seven-coordinate complexes (L—L)M(CO)3X2 (M = Mo, W; X = Br, I; (L—L) = cis-(CH3)2AsC(CF3)=C(CF3)As(CH3)2) were prepared and characterized. 1H and 13C nmr studies at 25 and −70 °C suggest that the complexes are nonrigid. Similarly 1H nmr studies indicate the seven-coordinate (L—L)LMo(CO)2Br2 complexes are also nonrigid. The (L—L)L2Mo(CO)Br2 complexes (L is a monodentate phosphite or phosphine) are rigid at 25 °C and nonrigid at higher temperatures. Activation parameters are calculated for the motion of two of the complexes and possible mechanisms are discussed.

Modes of Xanthine Complexation to Dirhodium Tetrakis[(R)-α-methoxy-α- (trifluoromethyl)-phenylacetate] in Solution and in the Solid State

2001 ◽  
Vol 56 (3) ◽  
pp. 319-324 ◽  
Author(s):  
Sven Rockitt ◽  
Rudolf Wartchow ◽  
Helmut Duddeck ◽  
Anna Drabczynska ◽  
Katarzyna Kiec-Kononowicz
Keyword(s):  
Solid State ◽  
Diffraction Analysis ◽  
Carbonyl Group ◽  
Enantiomeric Excess ◽  
Carbonyl Groups ◽  
X Ray Diffraction ◽  
Nmr Studies ◽  
X Ray ◽  
C Nmr

Abstract It is show n by IR and NMR studies that the xanthines 1-5 prefer a side-on com plexation to the chiral dirhodium tetrakis[(R)-α-methoxy-α-(trifluoromethyl)phenylacetatel (Rh*) in solution whereas carbonyl groups are involved in the solid state. For 6, at least the carbonyl group C-6 contributes to complexation in solution as well. A lternating strands of 6 and Rh* exist in the solid state as revealed by X-ray diffraction analysis described in detail. The determination of enantiomeric excess of the chiral xanthine 6 can easily be accomplished by the “dirhodium method ” (1H and 13C NMR in the presence of Rh*).

In Search of New Approaches to Asymmetric Conjugate Addition: Screening Studies on the Use of [Zn(bpy*)X(R)] Reagents and α,β-Unsaturated Amide Michael Acceptors

2007 ◽  
Vol 72 (8) ◽  
pp. 1107-1121 ◽  
Author(s):  
Alexander J. Blake ◽  
Daniela Giunta ◽  
Jonathan Shannon ◽  
Maurizio Solinas ◽  
Francesca Walzer ◽  
...  
Keyword(s):  
Ligand Exchange ◽  
Conjugate Addition ◽  
Nmr Studies ◽  
Conjugate Additions ◽  
New Approaches ◽  
Michael Acceptors ◽  
Derivatives Of ◽  
Moderate Yield ◽  
C Nmr

Conjugate additions of [Zn(bpy*)Cl(Et)] (bpy* = 4,4'-di-tert-butyl-2,2'-bipyridine) to cyclohex-2-en-1-one are promoted by ZnMe2 in 88% ee but in moderate yield under CuI phosphoramidite catalysis. In the absence of ZnMe2 the [Zn(bpy*)Cl(Et)] is inactive indicating a Schlenk-type equilibrium. Other derivatives of [Zn(bpy*)Cl(R)] (R = Bu, 4-methylbenzyl), prepared in situ from [ZnCl(R)] and the bipyridine give low yields due to competing chloride abstraction. 13C NMR studies indicate facile organo-ligand exchange between [Zn(bpy*)(Et)2] and [Zn(bpy*)Cl2] complexes. In the presence of the bipyridine, [ZnBr(allyl)] disproportionates into [Zn(bpy*)Br2] and [Zn(bpy*)(allyl)2] species. In separate studies, simple (E)-MeCH=CHCONMeR (R = Me, OMe) α,β-unsaturated amides undergo asymmetric 1,4-addition of EtMgBr in 75-99% yield and 48-79% ee in the presence of the diphosphines JosiPhos or MeDuPhos and copper(I) sources.

Structural determination of the polysaccharide antigens of Neisseria meningitidis serogroups Y, W-135, and BO

1976 ◽  
Vol 54 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Apurba K. Bhattacharjee ◽  
Harold J. Jennings ◽  
C. Paul Kenny ◽  
Adèle Martin ◽  
Ian C. P. Smith
Keyword(s):  
Sialic Acid ◽  
Acetyl Derivative ◽  
Major Product ◽  
Hydroxyl Group ◽  
Nmr Studies ◽  
Acetylneuraminic Acid ◽  
Nmr Data ◽  
Polysaccharide Antigens ◽  
C Nmr

The purified high molecular weight serogoup Y meningococcal polysaccharide contains equimolar proportions of D-glucose and N-acetylneuraminic acid and is partially O-acetylated. Carbon-13 nuclear magnetic resonance (NMR) studies, together with other chemical data, have indicated that the polysaccharide is linked only at C-6 of the D-glucose and C-4 of the sialic acid residues, all the linkages being in the α-configuration. The 13C NMR data also indicated that the Y polysaccharide is composed of an alternating sequence of these two different residues, and this was confirmed by its autohydrolysis where the major product was 4-O-α-D-glucopyranosyl-β-D-N-acetylneuraminic acid. The W-135 polysaccharide differs from that of Y only in the absence of O-acetylation and in the configuration of one hydroxyl group of the disaccharide repeating unit. In this case autohydrolysis yielded 4-O-α-D-galactopyranosyl-β-D-N-acetylneuraminic acid as the major product. Structural evidence indicates that the BO and Y polysaccharides are identical.Methanolysis of the Y polysaccharide yielded in addition to the methyl glycosides of glucose and sialic acid, a 9-O-acetyl derivative of the latter. This derivative was formed during the re-N-acetylation process and its formation was mainly due to the presence of sodium ions in the original polysaccharide.

scholarly journals Synthesis, Characterisation and Hydrolytic Reactions of the First Pentaisopropoxostannate Derivatives of Magnesium, Zinc and Cadmium

2007 ◽  
Vol 2007 (8) ◽  
pp. 458-460
Author(s):  
Jayshree Shahanl ◽  
Anirudh Singh
Keyword(s):  
Molecular Weight ◽  
Nmr Studies ◽  
Molar Ratios ◽  
Derivatives Of ◽  
C Nmr

Pentaisopropoxostannate derivatives of the types [{M[Sn(OPri)5](μ–Cl)}2] and [M{Sn(OPri)5}2] have been prepared by the reactions of MCl2 (M = Mg, Zn, and Cd) with NaSn(OPri)5 in 1:1 and 1:2 molar ratios, respectively, in benzene. All these derivatives have been characterised by elemental and isopropoxo group analyses, spectroscopic (IR, 1H and 13C NMR) studies, and molecular weight determinations. Two typical hydrolytic reactions of [Zn{Sn(OPri)5}2] have also been investigated.

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