Carbon‐13 NMR of quinone methides

Benson, Mabry; Jurd, L.

doi:10.1002/mrc.1270220206

Cited by 7 publications

(3 citation statements)

References 17 publications

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“…3H NMR (CDCI3) 6 1.72 (m, 4 H, 2 x CH2), 2.60 (m, 4 H, 2 x benzyl CH2), 5.15 (s, 2H, 2 x OH), 6.55 (s, 2H, 2 x ArH); UV (CH3CN) 210, 226, 288 nm; GC-MS, El m/z 164 (75) (M). 4-Cinnamylcatechol (3) was synthesized by condensing catechol with cinnamic alcohol as described previously (10). *H NMR (CDC13) d 3.44 (d, J = 6 Hz, 2H, CH2), 6.38 (m, 1H, vinyl CH), 6.77 (m, 1H, vinyl CH), 7.2-7.4 (m, 8H, ArH); UV (CH3OH) 206, 252, 284 nm; GC-MS, El m/z 226 (100) (M).…”

Section: Methodsmentioning

confidence: 99%

The Influence of the p-Alkyl Substituent on the Isomerization of o-Quinones to p-Quinone Methides: Potential Bioactivation Mechanism for Catechols

Iverson¹,

Hu²,

Vukomanovic³

et al. 1995

Chem. Res. Toxicol.

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Previously, we have shown that an additional bioactivation pathway for the hepatocarcinogen safrole (1-allyl-3,4-(methylenedioxy)benzene) exists which may contribute to its toxic effects: initial O-dealkylation of the methylenedioxy ring, forming the catechol, hydroxychavicol (HC, 1-allyl-3,4-dihydroxybenzene), 2-electron oxidation to the o-quinone (4-allyl-3,5-cyclohexadien-1,2-dione), and isomerization, forming the more electrophilic p-quinone methide (2-hydroxy-4-allylidene-2,5-cyclohexadien-1-one) [Bolton, J. L., Acay, N. M., & Vukomanovic, V. (1994) Chem. Res. Toxicol. 7, 443-450]. In the present investigation, we explored the effects of changing pi-conjugation at the 4-position on both the rate of isomerization of the initially formed o-quinones to the QMs and the reactivity of the quinoids formed from 4-propylcatechol (1), 2,3-dihydroxy-5,6,7,8-tetrahydronaphthalene (2), and 4-cinnamylcatechol (3). We selectively oxidized the catechols to the corresponding o-quinones or p-quinone methides and trapped these reactive electrophiles with glutathione (GSH). The GSH adducts were fully characterized by UV, NMR, and mass spectrometry. Microsomal incubations with the parent catechols in the presence of glutathione produced only o-quinone glutathione conjugates. However, if the trapping agent (GSH) was added after an initial incubation time, both o-quinone and p-quinone methide GSH conjugates were observed. The results indicate that extended pi-conjugation at the para position enhances the rate of isomerization of the o-quinone to the quinone methide. Thus the half-life of the o-quinones decreased in the following order: the o-quinone of 1 > 2 > HC > 3.(ABSTRACT TRUNCATED AT 250 WORDS)

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Section: Methodsmentioning

confidence: 99%

The Influence of the p-Alkyl Substituent on the Isomerization of o-Quinones to p-Quinone Methides: Potential Bioactivation Mechanism for Catechols

Iverson¹,

Hu²,

Vukomanovic³

et al. 1995

Chem. Res. Toxicol.

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“…For a comparison, the C═O chemical shift of o-quinone methides is~186 ppm. [17] Considering that the chemical shift of ohydroxyacetophenone is 204.5 ppm, [18] whereas that of o-hydroxythioacetophenone is 235 ppm, [6] an estimate of the C═S chemical shift of the B form of 221 ppm can be made. The observed value of~166 ppm suggests that the A form dominates.…”

Section: Discussionmentioning

confidence: 99%

“…The C‐1 (C═S) chemical shift is unusually low (~166 ppm). For a comparison, the C═O chemical shift of o‐quinone methides is ~186 ppm . Considering that the chemical shift of o ‐hydroxyacetophenone is 204.5 ppm, whereas that of o ‐hydroxythioacetophenone is 235 ppm, an estimate of the C═S chemical shift of the B form of 221 ppm can be made.…”

Section: Discussionmentioning

confidence: 99%

NMR, MP2, and DFT study of thiophenoxyketenimines (o‐thio‐Schiff bases): Determination of the preferred form

Saeed

Elias

Kamounah

et al. 2017

Magnetic Reson in Chemistry

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Five new thiophenoxyketinimines have been synthesized. H and C NMR spectra as well as deuterium isotope effects on C chemical shifts are determined, and spectra are assigned. DFT and MP2 calculations of both structures, chemical shifts, and isotope effects on chemical shifts are done. The combined analysis reveals that the compounds are primarily on a zwitterionic form with an NH and a S group and with a little of the neutral form mixed in. Very strong intramolecular hydrogen bonding is found and very high NH chemical shifts are observed. The theoretical calculations show that calculations at the MP2 level are best to obtain correct "C═S" chemical shifts.

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Epoxidation von 2‐Methyl‐3‐phenylbenzofuranen mit Dimethyldioxiran: eine neuartige reversible Valenzisomerisierung zwischen Benzofuranepoxiden und Chinonmethiden, deren Umlagerungen, Methanolyse und Cycloadditionschemie

et al. 1993

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Carbon‐13 NMR of quinone methides

Cited by 7 publications

References 17 publications

The Influence of the p-Alkyl Substituent on the Isomerization of o-Quinones to p-Quinone Methides: Potential Bioactivation Mechanism for Catechols

The Influence of the p-Alkyl Substituent on the Isomerization of o-Quinones to p-Quinone Methides: Potential Bioactivation Mechanism for Catechols

NMR, MP2, and DFT study of thiophenoxyketenimines (o‐thio‐Schiff bases): Determination of the preferred form

Epoxidation von 2‐Methyl‐3‐phenylbenzofuranen mit Dimethyldioxiran: eine neuartige reversible Valenzisomerisierung zwischen Benzofuranepoxiden und Chinonmethiden, deren Umlagerungen, Methanolyse und Cycloadditionschemie

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