Conformational preferences about both exocyclic carbon–carbon bonds in some phenyl derivatives of ethane, propene, and 4-picoline

The 1H nmr spectra in solution of 1-R-(3,5-dibromophenyl) ethanes (R = CH3, C2H5, n-C3H7 to n-C6H13, OH, F, Br), of 1-amino-2-(3,5-dichlorophenyl) ethane, of 3,5-dichloroallylbenzene, and of 4-(3,5-dibromobenzyl) pyridine are analyzed at 305 K. For the ethane derivatives, the populations of anti and gauche conformers are derived from the vicinal proton–proton coupling constants. The conformation about the C1—Cα bond in both gauche and anti forms is discussed in terms of long-range couplings to the ring protons and some approximate barriers about this bond are suggested for both conformers. Greater rigidity exists in the gauche than in the anti conformations. In some cases the measurements are compared with extensive molecular orbital calculations, for example, for phenethylamine. The low-energy conformations and the barriers about the C1—Cα bond are deduced for the allyl and pyridyl compounds.

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Solution Conformation of Benzimidazole Nucleosides with the Aid of Model Analogues

Zeitschrift für Naturforschung C ◽

10.1515/znc-1981-1-223 ◽

1981 ◽

Vol 36 (1-2) ◽

pp. 126-134 ◽

Cited By ~ 5

Author(s):

Zygmunt Kazimierczuk ◽

Ryszard Stolarski ◽

Lech Dudycz ◽

David Shugar

Keyword(s):

Chemical Shifts ◽

Coupling Constants ◽

Glycosidic Bond ◽

Benzimidazole Ring ◽

Proton Proton ◽

H Nmr ◽

Proton Coupling ◽

Vicinal Proton ◽

Sugar Ring ◽

Derivatives Of

Abstract The 4,6-dibromo-and 5,7-dibromo-derivatives of 1-β-ᴅ-ribofuranosylbenzimidazole, and the 4,6-dibromo-derivative of 1-α-ᴅ-arabinofuranosylbenzimidazole, have been synthesized by condensation of the trimethylsilylated derivative of 4,6-dibromobenzimidazole with the appropriate protected sugar in the presence of SnCl4. Application of the fusion method led to the β-ribofuranoside of 2-methyl-5,6-dichlorobenzimidazole. Two additional analogues of the biologically active ribofuranoside of 5,6-dichlorobenzimidazole, viz. the 2′,3′-O-isopropylidene and the 5′-chloro-5′-deoxy derivatives have been synthesized. Analyses of the 1H NMR spectra of the foregoing, and of previously synthesized 5(6)-mono-halogeno and 5,6-dihalogeno derivatives, were employed to determine solution conformations of these nucleosides. Conformations of the sugar rings and exocyclic groups were evaluated from vicinal proton-proton coupling constants, as for purine nucleosides. The conformation of the benzimidazole ring about the glycosidic bond was determined from the chemical shifts of the sugar protons, principally H(2′), with the aid of model analogues in fixed syn and anti conformations; and, independently, from the chemical shifts of the benzimidazole ring protons, principally H(4) and H(7). The halogenated benzimidazole ribofuranosides exhibit conformations of the sugar ring similar to those for purine β-nucleosides, but differ from the latter in their preference for the conformation syn about the glycosidic bond.

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The synthesis and the nuclear magnetic resonance study of β-lactam derivatives of 1,5-benzothiazepines

Canadian Journal of Chemistry ◽

10.1139/v88-047 ◽

1988 ◽

Vol 66 (2) ◽

pp. 279-282 ◽

Cited By ~ 25

Author(s):

Aron Szöllösy ◽

George Kotovych ◽

Gábor Tóth ◽

Albert Lévai

Keyword(s):

Nuclear Overhauser Effect ◽

Nuclear Magnetic Resonance Study ◽

Coupling Constants ◽

Magnetic Resonance Study ◽

Proton Proton ◽

Proton Coupling ◽

Overhauser Effect ◽

Vicinal Proton ◽

Nuclear Overhauser ◽

Derivatives Of

The synthesis and stereochemistry of seven β-lactam derivatives of 1,5-benzothiazepines are presented. The configurational and conformational analysis is based on nuclear Overhauser effect experiments, together with analysis of the vicinal proton–proton coupling constants. In the preferred conformation, the seven-membered ring is in a half-chair. Only for one compound, 2-aza-4-bromo-4-methyl-5,7-diphenyl-8-thiatricyclo[7.4.0.02,5]trideca-Δ1,9,10,12-trien-3-one, were two diastereomers isolated (compounds 6a and 6b). Six of the compounds have the 4S*, 5R*, 7R* configuration while compound 6b has the 4R*, 5R*,7R* configuration.

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Long-range Proton–Proton Coupling Constants in the Vinylpyridines. Conformational Preferences of the Vinyl Group and Molecular Orbital Calculations

Canadian Journal of Chemistry ◽

10.1139/v74-021 ◽

1974 ◽

Vol 52 (1) ◽

pp. 136-142 ◽

Cited By ~ 11

Author(s):

J. Brian Rowbotham ◽

Ted Schaefer

Keyword(s):

Molecular Orbital ◽

Long Range ◽

Coupling Constants ◽

Graphical Form ◽

Molecular Orbital Calculations ◽

Proton Proton ◽

Meta Position ◽

Proton Coupling ◽

Conformational Preferences ◽

Vinyl Group

The p.m.r. spectra of 2-vinylpyridine, 2-methyl-5-vinylpyridine, and 4-vinylpyridine are examined for long-range coupling constants between the vinylic and ring protons. Those over six, seven, and eight bonds from the vinyl group to ring or methyl protons in the para position are dominated by a π electron mechanism. Those over five bonds between the α proton and a ring proton in the meta position indicate that the vinyl group prefers to lie cis to the nitrogen in 2-vinylpyridine but trans in the 5-vinylpyridine. INDO-MO-FPT calculations of coupling constants between vinyl protons and ring protons, carbon-13, and nitrogen-14 nuclei are presented in graphical form.

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ChemInform Abstract: LONG-RANGE PROTON-PROTON COUPLING CONSTANTS IN THE VINYLPYRIDINES, CONFORMATIONAL PREFERENCES OF THE VINYL GROUP AND MOLECULAR ORBITAL CALCULATIONS

Chemischer Informationsdienst ◽

10.1002/chin.197415067 ◽

1974 ◽

Vol 5 (15) ◽

Author(s):

J. BRIAN ROWBOTHAM ◽

TED SCHAEFER

Keyword(s):

Molecular Orbital ◽

Long Range ◽

Coupling Constants ◽

Molecular Orbital Calculations ◽

Proton Proton ◽

Proton Coupling ◽

Conformational Preferences ◽

Vinyl Group

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21,22-Disubstituted 18α,19βH-Ursane Derivatives with Oxabicyclooctane System in Ring E

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19930173 ◽

1993 ◽

Vol 58 (1) ◽

pp. 173-190 ◽

Cited By ~ 1

Author(s):

Eva Klinotová ◽

Jiří Klinot ◽

Václav Křeček ◽

Miloš Buděšínský ◽

Bohumil Máca

Keyword(s):

Spectral Data ◽

Spin Systems ◽

Coupling Constants ◽

Complete Analysis ◽

Nmr Spectrum ◽

Proton Proton ◽

H Nmr ◽

Proton Coupling ◽

C Nmr

Reaction of 3β-acetoxy-21,22-dioxo-18α,19βH-ursan-28,20β-olide (IIIa) and 20β,28-epoxy-21,22-dioxo-19α,19βH-ursan-3β-yl acetate (IIIb) with diazomethane afforded derivatives XII-XIV with spiroepoxide group in position 21 or 22, which were further converted into hydroxy derivatives XV and XVII. Ethylene ketals VIII-X were also prepared. In connection with the determination of position and configuration of the functional groups at C(21) and C(22), the 1H and 13C NMR spectral data of the prepared compounds are discussed. Complete analysis of two four-spin systems in the 1H NMR spectrum of bisethylenedioxy derivative Xb led to the proton-proton coupling constants from which the structure with two 1,4-dioxane rings condensed with ring E, and their conformation, was derived.

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Proton magnetic resonance study of the conformation of the pyrrolidine ring in some proline-thiohydantoins

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19882503 ◽

1988 ◽

Vol 53 (11) ◽

pp. 2503-2510 ◽

Cited By ~ 3

Author(s):

Jef J. M. Sleeckx ◽

Marc J. O. Anteunis ◽

Frans A. M. Borremans

Keyword(s):

Present Model ◽

Coupling Constants ◽

Proton Proton ◽

Proton Coupling ◽

Proton Magnetic Resonance Study ◽

Vicinal Proton ◽

Different Temperatures ◽

Experimental Justification ◽

State Assumption ◽

Methyl Phenyl

The conformational behaviour of a series of N-substituted thiohydantoins of proline was studied by proton NMR. The pseudorotational parameters of the proline moiety were calculated from the ten vicinal proton-proton coupling constants assuming a two state equilibrium (N ⇋ S). The effect of the different substituents (methyl, phenyl, para-nitrophenyl) at the thiohydantoin nitrogen on the conformation of the pyrrolidine rings is discussed. The spectra of proline-N-methylthiohydantoin were recorded at different temperatures in octadeuterotoluene solution. The conformational analysis of these spectra showed that the ratio of the populations of the N and S forms changes considerably with temperature, while the conformational identity of both the N and S forms remains strictly preserved. These facts provide an additional experimental justification of the two-state assumption, at least so for the present model compounds.

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