Carbon-13 n.m.r. Spectroscopy of pyrazole and some substituted pyrazoles

Rees, R. G.; Green, M. J.

doi:10.1039/j2968000387a

Cited by 11 publications

(5 citation statements)

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“…In any case, the result is in accord with previous results, being positive on N-3, negative on C-4, and positive on C-5.24 In parts per million relative to tetramethylsilane (TMS). 6 Parenthetical values are for CH2C12 as solvent. " In parts per million relative to tetramethylsilane (TMS).6 The assignments of the ortho and meta carbons are not certain and may be reversed.…”

Section: Resultsmentioning

confidence: 99%

Carbon-13 magnetic resonance studies of azoles. Tautomerism, shift reagent effects, and solvent effects

Elguero¹,

Marzin²,

Roberts³

1974

J. Org. Chem.

206

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The effects of substitution, lanthanide-shift reagents, solvent changes, and tautomerism were investigated on the 13C chemical shifts of pyrrole, pyrazole, imidazole, s-and u-triazole, and tetrazole. It was concluded that 1SC chemical shifts are of limited value to ascertain the positions of tautomeric equilibrium for rapidly interconverting azole tautomers.Several molecules in the five-membered N-heterocycle series have been investigated by means of their 13C nuclear magnetic resonance, but not in a systematic way: pyrrole as a neat liquid3 or in acetone;4 pyrazole in water,5 in acetone,4•6 and some of its N-substituted derivatives as neat liquids;6'7 imidazole in water,5•8 acetone,4 and ethanol;9 1,2,3-triazole in acetone;4 1,2,4-triazole in acetone4 or in dimethyl sulfoxide;10 and tetrazole in dimethyl sulfoxide.4 However, in none of these researches have the 13C nmr data been used to study tautomerism. Although a great deal of work has been done on the annular tautomerism of such azoles11 by various methods, often no definite conclusions can be reached. We will give attention here to the usefulness of 13C spectroscopy in the determination of tautomeric equilibrium constants compared with 1H or 14N spectroscopy.

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Section: Resultsmentioning

confidence: 99%

Carbon-13 magnetic resonance studies of azoles. Tautomerism, shift reagent effects, and solvent effects

Elguero¹,

Marzin²,

Roberts³

1974

J. Org. Chem.

206

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“…Proton nlnr alkyl shifts have proved useful for compounds [9][10][11][12] we have now found that the distinguishing between N-alkyl isomers in the correlation previously noted (1) is reversed due azole series due to increased shielding of the to the anisotropic effects of the 5-hydrazono alkyl group in the structural units (1) substituent a t the 1-N-alkyl site. As far as we are However, these trends may break down when substituents containing special anisotropic effects are present.…”

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confidence: 80%

Comparison of ¹³C and ¹H N-alkyl shifts of isomeric alkyl tetrazoles: some ambident benzylations

Butler¹,

McEvoy²,

Scott³

et al. 1977

Can. J. Chem.

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“…The residue was dissolved in 5 ml of 7.5% EtOAc in CHCI3 and passed through the SEP-PAK cartridge (13). The SEP-PAK was rinsed with another 8 ml of the same solvent.…”

Section: Methodsmentioning

confidence: 99%

Complex Acetylenes from the Roots ofFerula communis

Teresa

Villaseco²,

Hernández³

et al. 1986

Planta Med

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The benzene extract from the roots of FERULA COMMUNIS afforded the coumarin ferulenol ( 1) and the structurally related acetylenes named ferulinolone [3-(1,2-dihydrofalcarinolonyl)-ferulenol] ( 4) and decarboxyferulinolone [2-nor-3-(1,2-dihydrofal-carinolonyl-ferulenol] ( 7). The structures of these substances were deduced from their spectral data and those of their derivatives, mainly from the (1)H- and (13)C-NMR 1D and 2D spectra (one bond and long-range correlations). Methoxylatifolone ( 10) was also isolated from this extract.

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Carbon-13 n.m.r. Spectroscopy of pyrazole and some substituted pyrazoles

Abstract: The use of carbon-13 n.m.r. spectroscopy in pyrazole chemistry is demonstrated, and the results are shown to be in agreement with previously known physicochemical data,

Cited by 11 publications

References 0 publications

Carbon-13 magnetic resonance studies of azoles. Tautomerism, shift reagent effects, and solvent effects

Carbon-13 magnetic resonance studies of azoles. Tautomerism, shift reagent effects, and solvent effects

Comparison of ¹³C and ¹H N-alkyl shifts of isomeric alkyl tetrazoles: some ambident benzylations

Complex Acetylenes from the Roots ofFerula communis

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Carbon-13 n.m.r. Spectroscopy of pyrazole and some substituted pyrazoles

Abstract: The use of carbon-13 n.m.r. spectroscopy in pyrazole chemistry is demonstrated, and the results are shown to be in agreement with previously known physicochemical data,

Cited by 11 publications

References 0 publications

Carbon-13 magnetic resonance studies of azoles. Tautomerism, shift reagent effects, and solvent effects

Carbon-13 magnetic resonance studies of azoles. Tautomerism, shift reagent effects, and solvent effects

Comparison of 13C and 1H N-alkyl shifts of isomeric alkyl tetrazoles: some ambident benzylations

Complex Acetylenes from the Roots ofFerula communis

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Comparison of ¹³C and ¹H N-alkyl shifts of isomeric alkyl tetrazoles: some ambident benzylations