The conformational preference of methoxyl and acetoxyl groups in 3-oxycyclohexenes, 2-oxymethylenecyclohexanes, and 1-oxytetralins and the generalized anomeric effect

1987 ◽  
Vol 65 (8) ◽  
pp. 1761-1768 ◽  
Author(s):  
Adama Ouédraogo ◽  
Minh Tan Phan Viet ◽  
John K. Saunders ◽  
Jean Lessard
Keyword(s):  
Methoxyl Group ◽  
Equatorial Orientation ◽  
Anomeric Effect ◽  
Conformational Preference ◽  
Magnetic Resonance Data ◽  
Conformational Effect ◽  
Axial Conformer ◽  
Resonance Data ◽  
Cis And Trans ◽  
Derivatives Of

The 13C and 1H nuclear magnetic resonance data of 3-oxycyclohexenes, 2-oxymethylenecyclohexanes, and 1-oxytetralins show (i) that the pseudoaxial preference is larger for the acetoxyl group than for the methoxyl group in 3-oxycyclohexenes, (ii) that the methoxyl and the acetoxyl groups have the same pseudoaxial preference in 1-oxytetralins, and (iii) that in 2-oxymethylenecyclohexanes, the acetoxyl group prefers the equatorial orientation whereas the methoxyl group prefers to be axial. These results are interpreted in terms of the orbital picture (π–σ* stabilization of the axial conformer) of the generalized anomeric effect to which is opposed a conformational effect termed the "unsaturation effect" in 2-acetoxymethylenecyclo-hexane and probably also, but to a much smaller extent, in 1-acetoxytetralin. The results also show that cis and transtert-butyl analogues of 3-oxycyclohexenes do not represent the true limit conformers whereas cis and trans 4-tert-butyl derivatives of 2-oxymethylenecyclohexanes do not differ drastically from the limit conformers.

Conformational analysis of 2-substituted methylenecyclohexanes and 3-substituted cyclohexenes and the anomeric effect

1977 ◽  
Vol 55 (6) ◽  
pp. 1015-1023 ◽  
Author(s):  
Jean Lessard ◽  
Phan Viet Minh Tan ◽  
Robert Martino ◽  
John K. Saunders
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Double Bond ◽  
Magnetic Resonance ◽  
Conformational Analysis ◽  
Methoxy Group ◽  
Anomeric Effect ◽  
Magnetic Resonance Data ◽  
Electronegative Substituent ◽  
Axial Conformer ◽  
Resonance Data

The analysis of the 13C and 1H nuclear magnetic resonance data of 2-substituted methylenecyclohexanes and 3-substituted cyclohexenes demonstrates that a double bond stabilizes the axial conformer for an electronegative substituent. Introduction of a methoxy group on the double bond further increases the relative stability of the axial conformer. These results are interpreted in terms of the 'double bond – no bond' resonance.

Cycloaddition d'ylures d'azométhine dérivés de la 3,4-dihydro-6,7-diméthoxy-3-méthoxycarbonyl-isoquinoléine

1991 ◽  
Vol 69 (7) ◽  
pp. 1156-1160 ◽  
Author(s):  
Tahar Lakhlifi ◽  
Ahmed Sedqui ◽  
Bernard Laude ◽  
Nguyen Dinh An ◽  
Joël Vebrel
Keyword(s):  
Magnetic Resonance ◽  
Key Words ◽  
Proton Magnetic Resonance ◽  
Azomethine Ylide ◽  
Magnetic Resonance Data ◽  
Resonance Data ◽  
Azabicyclic Compounds ◽  
Derivatives Of ◽  
Proton Magnetic Resonance Data

Three azomethine ylide precursors including the methyl 3,4-dihydro-6,7-dimethoxyisoquinoline-3carboxylate moiety were synthesized. The 1,3-dipolar species formed from these products react with activated dipolarophilic olefines leading diastereospecifically to derivatives of 4′,5′-dimethoxy-1,2-benzo-4,7-imino-4-methoxycarbonyl-1-cycloheptene. Proton magnetic resonance data allowed the determination of the stereochemistry of the cycloadducts. Key words: cyclic azomethine ylide, azabicyclic compounds, stereochemistry.

Photo-additions of aromatic hydrocarbons—indene and naphthalene with acrylonitrile

1969 ◽  
Vol 47 (5) ◽  
pp. 757-766 ◽  
Author(s):  
John J. McCullough ◽  
C. W. Huang
Keyword(s):  
Butyl Alcohol ◽  
Major Product ◽  
Minor Amount ◽  
Strong Base ◽  
Magnetic Resonance Data ◽  
Cis And Trans Isomers ◽  
Resonance Data ◽  
Ethanol Yields ◽  
A Minor ◽  
Cis And Trans

The photolyses of indene and naphthalene with acrylonitrile have been studied, and the products characterized. Indene reacts with acrylonitrile when the hydrocarbon absorbs light, or when a triplet sensitizer (acetophenone) is absorbing. Photolysis under the former conditions in ethanol yields 2-(1-indenylpropionitrile) (70%), 2-(3-indenylpropionitrile) (10%), and 6-cyano-2,3-benzobicyclo[3,2,0]hept-2-ene (20%). Base-catalyzed isomerizations of the substituted indenes are reported. On sensitization, cis- and trans-isomers of 7-cyano-2,3-benzobicyclo[3,2,0]hept-2-ene are formed, with a minor amount of indene dimer. The former isomers can be equilibrated with strong base. Adducts of 1,1-dimethyl- and 1,1-diphenylindene with acrylonitrile are also described, and nuclear magnetic resonance data reported. Naphthalene adds acrylonitrile on photolysis in t-butyl alcohol (pyrex filter) to afford trans-8-cyano-2,3-benzobicyclo-[4,2,0]-octa-2,4-diene (90%) and 1- and 2-naphthyl-2-propionitrile (10%). Sensitization with acetophenone gave no detectable products. Irradiation of the major product at 253.7 mμ through Vycor gave naphthalene. The preparative value of these reactions is considered and possible mechanisms are proposed.

Orientation of the methoxyl group in cis- and trans-2-methoxy-4-methyl-1,3-dioxanes and related compounds as inferred by 1H and 13C nmr spectroscopy. The significance of the "exo-anomeric" effect

1982 ◽  
Vol 60 (9) ◽  
pp. 1067-1072 ◽  
Author(s):  
Vanga S. Rao
Keyword(s):  
Dynamic Equilibrium ◽  
Chemical Shifts ◽  
13C Nmr Spectroscopy ◽  
Methoxyl Group ◽  
Anomeric Effect ◽  
1H And 13C Nmr ◽  
Nuclear Overhauser ◽  
Cis And Trans ◽  
In Cis ◽  
Related Compounds

Carbon-13 chemical shifts and 13C—1H couplings are reported for some substituted 2-methoxy-1,3-dioxanes and related tetrahydropyran derivatives. These data, together with nuclear Overhauser enhancement experiments, provided evidence for a favored orientation of the methoxyl group. From an analysis of the 13C chemical shifts and the magnitude of vicinal 13C—1H coupling between —OCH3 and H-2, a possible dynamic-equilibrium orientation for the methoxyl group is proposed, and an evaluation of the significance of a "generalized exo-anomeric effect" is presented.

Fluorinated carbohydrates. Part V. Nuclear magnetic resonance data on pyranose and furanose derivatives of 3-deoxy-3-fluoro-D-glucose

1970 ◽  
Vol 48 (24) ◽  
pp. 3937-3945 ◽  
Author(s):  
A. B. Foster ◽  
R. Hems ◽  
L. D. Hall
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nuclear Magnetic Resonance Data ◽  
Spectral Parameters ◽  
Magnetic Resonance Data ◽  
Resonance Data ◽  
Derivatives Of ◽  
Glucose Derivatives ◽  
Nuclear Magnetic

The n.m.r. spectra of a series of 3-fluorinated glucose derivatives have been measured; spectral assignments were confirmed by 1H–{19F} heteronuclear decoupling experiments. The 19F spectral parameters illustrate a variety of stereospecific dependencies, the most noteworthy being that of 4JF,H couplings, for which 4Je,e = ca. + 4.0 Hz while 4Je,a = ca. − 1.5 Hz.

Carbon-13 nuclear magnetic resonance study of phenyl derivatives of B, Si, Sn, P, and Te fluorides

1993 ◽  
Vol 71 (4) ◽  
pp. 526-528 ◽  
Author(s):  
Chengrui Wang ◽  
Yuxiang Mo ◽  
Meehae Jang ◽  
Alexander F. Janzen
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Central Element ◽  
Nuclear Magnetic Resonance Study ◽  
Magnetic Resonance Data ◽  
Resonance Data ◽  
Experimental Values ◽  
Derivatives Of ◽  
Nuclear Magnetic

13C nuclear magnetic resonance data for a variety of phenyl derivatives of boron, silicon, tin, phosphorus, and tellurium fluorides are presented. Neutral, anionic, and cationic complexes are included and the coordination number of the central element varies from 3 to 6. Empirical equations of the 13C chemical shifts of the benzene ring have been deduced by taking into consideration the charge density, dipole moment, and binding energy, and the 13C chemical shifts calculated from these equations deviate from the experimental values by up to 1.4 ppm, but mostly less than 0.7 ppm.

Solution structures of dimeric methylpyrazolyl and indazolyl dimethyl-derivatives of boron, gallium, and indium from 1H nuclear magnetic resonance data

1979 ◽  
Vol 57 (18) ◽  
pp. 2520-2522 ◽  
Author(s):  
Louis K. Peterson ◽  
Kwat I. Thé
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Single Species ◽  
Structural Isomer ◽  
Solution Structures ◽  
H Nmr ◽  
Magnetic Resonance Data ◽  
Nmr Data ◽  
1H Nuclear Magnetic Resonance ◽  
Resonance Data ◽  
Derivatives Of

Trimethylboron and trimethylgallium react with 3-methylpyrazole to yield isomer pairs of dimeric products [Me2E(Mepz)]2 (E = B, Ga; Mepz = 3-methylpyrazolyl), in the approximate ratios 4:3 (E = B) and 9:1 (E = Ga), while trimethylindium gives a single species. Reactions of indazole with trimethylgallium and trimethylindium also yield a single structural isomer of the dimer [Me2Eind]2 (E = Ga, In; ind = indazolyl). Solution structures were interpreted on the basis of 1H nmr data.

NEW REARRANGEMENTS OF THE CARYOPHYLLENE SKELETON: THE DINITROPHENYLHYDRAZONES FROM CARYOPHYLLENE OXIDE

1964 ◽  
Vol 42 (7) ◽  
pp. 1664-1675 ◽  
Author(s):  
E. W. Warnhoff
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nuclear Magnetic Resonance Data ◽  
Chemical Data ◽  
Caryophyllene Oxide ◽  
Magnetic Resonance Data ◽  
Resonance Data ◽  
Derivatives Of ◽  
Nuclear Magnetic

Caryophyllene oxide (I) and dihydrocaryophyllene oxide (II) have been found to give 2,4-dinitrophenylhydrazones. Structures IV, V, and VII are assigned to three of these compounds on the basis of nuclear magnetic resonance data, other spectral and chemical data, and mechanistic considerations. Structure VII is the product of a new cyclization–rearrangement of the caryophyllene system. The dinitrophenylhydrazone previously obtained from isocaryophyllene oxide-a (III) is probably identical with VII. Three other new derivatives of caryophyllene are described, one of which (VI) is an intermediate in the conversion of I to VII.

The conformational behaviour of 2-aryloxytetrahydropyrans and 2-acetoxytetrahydropyran, and barrier to ring inversion

1991 ◽  
Vol 69 (3) ◽  
pp. 474-480 ◽  
Author(s):  
Adama Ouedraogo ◽  
Jean Lessard
Keyword(s):  
Electrostatic Interactions ◽  
Conformational Equilibrium ◽  
Anomeric Effect ◽  
Inversion Barrier ◽  
Ring Inversion ◽  
Key Words 2 ◽  
Magnetic Resonance Data ◽  
Resonance Data ◽  
Electron Withdrawal ◽  
Effect Ring

The 13C nuclear magnetic resonance data of a series of 2-(4-substituted-phenoxy)tetrahydropyrans at 156 K and in CF2Br2 and CHFCl2 solvents show that the axial preference increases with electron withdrawal in the aryloxy group: from 79% (ΔG°E→A = −0.4 kcal mol−1) (4-OCH3) to 90% (ΔG°E→A = −0.7 kcal mol−1) (4-NO2) in CF2Br2. The axial preference (anomeric effect) is smaller in the more polar CHFCl2 solvent, as expected, and the substituent effect is smaller also: change in ΔG°E→A from −0.3 (4-OCH3) to −0.5 (4-NO2) kcal mol−1. However, the axial preference of 2-acetoxytetrahydropyran is shown to be smaller than that of 2-phenoxytetrahydropyran in CF2Br2 solvent although the acetoxy group is expected to be more electronegative than the phenoxy group. Furthermore, the polarity of the solvent has no effect on the conformational equilibrium of 2-acetoxytetrahydropyran. The results are interpreted in terms of both orbital and electrostatic interactions. The ring-inversion barrier of 2-alkoxy and 2-aryloxytetrahydropyrans, determined by the temperature-coalescence method, is lower than that of tetrahydropyran by about 1.5 kcal mol−1. Key words: 2-substituted tetrahydropyrans, conformational analysis, anomeric effect, ring inversion.

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