Phosphates d'énols-X. Détermination des isomères géométriques diversement substitués par résonance magnétique nucléaire

1973 ◽  
Vol 51 (20) ◽  
pp. 3412-3427 ◽  
Author(s):  
Emile M. Gaydou
Keyword(s):  
Double Bond ◽  
Coupling Constants ◽  
Factors Influencing ◽  
Shielding Constants ◽  
Résonance Magnétique

The E and Z configuration of enol phosphates substituted on the first carbon of the double bond are determined, in 27 cases, using [Formula: see text] coupling constants and the Tobey-Pascual substituent shielding constants method. The factors influencing [Formula: see text] and [Formula: see text] coupling constants are discussed.

Gradient-Enhanced Inverse-Detected NMR Techniquesfor Determination of 1H-15N Coupling Constants in 2,2-Dimethylpenta-3,4-dienal Derivatives

1997 ◽  
Vol 62 (11) ◽  
pp. 1747-1753 ◽  
Author(s):  
Radek Marek
Keyword(s):  
Double Bond ◽  
Chemical Shifts ◽  
Multiple Bond ◽  
Coupling Constants ◽  
Single Quantum ◽  
Nmr Techniques ◽  
Phase Sensitive ◽  
Heteronuclear Coupling

Determination of 15N chemical shifts and heteronuclear coupling constants of substituted 2,2-dimethylpenta-3,4-dienal hydrazones is presented. The chemical shifts were determined by gradient-enhanced inverse-detected NMR techniques and 1H-15N coupling constants were extracted from phase-sensitive gradient-enhanced single-quantum multiple bond correlation experiments. Stereospecific behaviour of the coupling constants 2J(1H,15N) and 1J(1H,13C) has been used to determine the configuration on a C=N double bond. The above-mentioned compounds exist predominantly as E isomers in deuteriochloroform.

15N, 13C, and 1H NMR Spectra of Azo and Hydrazo Compounds Derived from 1,3,3-Trimethyl-2-methylidene-2,3-dihydroindole (Fischer Base)

1998 ◽  
Vol 63 (7) ◽  
pp. 1012-1020 ◽  
Author(s):  
Antonín Lyčka ◽  
Josef Jirman ◽  
Alois Koloničný
Keyword(s):  
Double Bond ◽  
Hydrochloric Acid ◽  
Nmr Spectra ◽  
Coupling Constants ◽  
Azo Compounds ◽  
Passive Component ◽  
Geometric Isomers ◽  
H Nmr ◽  
Fischer Base ◽  
Hydrazone Form

The 15N, 13C, and 1H NMR spectra were measured for azo and hydrazo compounds derived from 1,3,3-trimethyl-2-methylidene-2,3-dihydroindole (Fischer base), which is a passive component with a terminal methylidene group. Products prepared by coupling in hydrochloric acid exist in the corresponding hydrazone form as the E-isomers. Neutralization gives a mixture of two isomeric azo compounds which differ in the arrangement at the C(2)=C(10) double bond. This mixture was alkylated with methyl iodide to obtain the =N-N(CH3)- hydrazone derivatives. The geometric isomers were resolved based on the NOESY approach and the stereospecific behaviour of the 2J(15N,13C) coupling constants was studied for the 15N-labelled compounds.

Structural trends of29Si-1H spin-spin coupling constants across double bond

2012 ◽  
Vol 50 (10) ◽  
pp. 665-671 ◽  
Author(s):  
Yury Yu. Rusakov ◽  
Leonid B. Krivdin ◽  
Valentina M. Nosova ◽  
Alexander V. Kisin ◽  
Valentin G. Lakhtin
Keyword(s):  
Double Bond ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

Etudes d'hétérocycles pentagonaux polyhétéroatomiques par résonance magnétique nucléaire du 13C. Thiazoles et thiazolo[2,3-e]tétrazoles

1978 ◽  
Vol 56 (1) ◽  
pp. 46-55 ◽  
Author(s):  
Robert Faure ◽  
Jean-Pierre Galy ◽  
Emile-Jean Vincent ◽  
José Elguero
Keyword(s):  
Electronic Structure ◽  
Comparative Study ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Coupling Constants ◽  
Thiazole Ring ◽  
Résonance Magnétique

Carbon-13 nmr spectra of 18 thiazoles with different substituents (R = CH3, C6H5, Cl, Br, NH2 et N3) have been recorded. The 13C chemical shifts and the nJ(C,H) coupling constants are discussed as a function of the nature of the substituent and the electronic structure of the thiazole ring. The 2-azido substituted thiazoles show azido-tetrazole isomerism, making possible a comparative study of substituent effects in thiazole and thiazolotetrazole rings. These studies have been extended to other heterocycles: benzothiazole, isothiazole, and isoxazole.

Hashish. 26. Factors influencing double-bond stability in cannabinoids

1981 ◽  
Vol 46 (5) ◽  
pp. 949-953 ◽  
Author(s):  
Haldean C. Dalzell ◽  
David B. Uliss ◽  
G. Richard Handrick ◽  
Raj K. Razdan
Keyword(s):  
Double Bond ◽  
Bond Stability ◽  
Factors Influencing

Hétérobicycles oxygénés. Synthèse d'alkyl-3,6,8-trioxabicyclo[3.2.1]octanes et d'alkyl-3,7,9 et -4,7,9-trioxabicyclo[4.2.1]nonanes

1978 ◽  
Vol 56 (17) ◽  
pp. 2292-2300 ◽  
Author(s):  
Pierre Calinaud ◽  
Jacques Gelas
Keyword(s):  
Double Bond ◽  
Carbon Atom ◽  
Nmr Spectra ◽  
Membered Ring ◽  
Coupling Constants ◽  
Basic Medium ◽  
Main Interest ◽  
Proton Coupling ◽  
Geminal Proton

The cyclization in a basic medium of 2 (or 4)-chloroalkyl-4 (or 2) -hydroxyalkyl-1,3-dioxolanes leads to bicyclic acetals, the 3,6,8-trioxabicyclo[3.2.1]octanes, which are useful intermediates for synthesis, yielding notably functionalized 1,4-dioxanes. The nmr spectra of these heterobicyclics were studied. The geminal proton coupling constants permit oneto distinguish between five- and six-membered rings and the determination of couplings over several bonds (4J and 5J) yields information concerning the conformation of the model bicyclics.Two isomeric series of alkylated bicyclic acetals (3,7,9- and 4,7,9-trioxabicyclo[4.2.1]nonanes) are accessible by the following routes: (a) the intramolecular addition of a 4-hydroxy-alkyl group to the ethylenic double bond on the carbon atom a to C-2 in the 1,3-dioxolanes; (b) the dechlorohydration of 2-chloromethyl-4-hydroxyalkyl-1,3-dioxolanes; (c) the dehydration of dioxolane-diols. The main interest in these heterobicyclics is to prepare a seven-membered ring and to be able to prepare functionalized 1,4-dioxepanes. [Journal translation]

The Reaction of 5-Substituted-2-Norbornenes with Phenylselenyl Chloride

2008 ◽  
Vol 61 (4) ◽  
pp. 283 ◽  
Author(s):  
D. Alan R. Happer ◽  
Thomas Francis ◽  
Jonathan M. White
Keyword(s):  
Double Bond ◽  
Product Distribution ◽  
Major Product ◽  
Factors Influencing

In dichloromethane, 5-substituted-2-norbornenes add phenylselenyl chloride across the double bond to give adducts in which the phenylselanyl substituent is exo and the chloro endo. The relative yields of the two regioisomeric adducts are reported for several of these. For most, the formation of the 2-chloro-3-phenyselanyl adduct is favoured. The main exceptions are when the 5-substituent is exo and a good resonance donor, where the 3-chloro-2-phenylselanyl adduct is the major product. Possible factors influencing the product distribution are discussed.

Reactions of stabilized phosphoranes with enol lactones

1977 ◽  
Vol 30 (7) ◽  
pp. 1629 ◽  
Author(s):  
PJ Babidge ◽  
RA Massy-Westropp
Keyword(s):  
Double Bond ◽  
Carbonyl Group ◽  
Ester Group ◽  
Carbonyl Groups ◽  
Ketone Group ◽  
Mild Conditions ◽  
Lactone Carbonyl ◽  
Factors Influencing ◽  
Group Reaction

Enol lactones in which the double bond is conjugated with an ester group react with ethoxycarbonyl-methylenetriphenylphosphoraneunder mild conditions to yield the normal Wittig product, derivedfrom the lactone carbonyl group. When the double bond is conjugated with a ketone group reaction occurs at both carbonyl groups. Factors influencing reactivity are discussed.

Preparation and Conformational Study of 19β,28-Epoxy-18α-olean-5-ene Derivatives

2006 ◽  
Vol 71 (3) ◽  
pp. 387-410 ◽  
Author(s):  
Martin Dračínský ◽  
Václav Richtr ◽  
Václav Křeček ◽  
Jan Sejbal ◽  
Jiří Klinot ◽  
...  
Keyword(s):  
Double Bond ◽  
Coupling Constants ◽  
Conformational Study ◽  
Hydrogen Atoms ◽  
Vicinal Coupling Constants ◽  
Starting Compound ◽  
New Type ◽  
Type 3

New oleanane type triterpenoids with the 5(6) double bond were prepared using partial demethylation on carbon C-4. The starting compound was 23-hydroxybetulin (1b) and the key reaction was the methylation of 19β,28-epoxy-24-nor-18α-olean-4-en-3-one (3b). The 5(6) double bond was used in preparation of new derivatives with an epoxy or oxo substituent in ring B. The conformation of ring A of new type 3-oxo oleanane derivatives with a double bond or a substituent on ring B was elucidated from vicinal coupling constants of hydrogen atoms in positions 1 and 2.

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