Syntheses of Cyclotene and Its Related Compounds

Tonari, Kennosuke; Ichimoto, Itsuo; Ueda, Hiroo; Tatsumi, Chuji

doi:10.1271/nogeikagaku1924.44.46

Cited by 3 publications

(3 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…An interesting synthesis, also employing oxalate was published as a patent by Krimen and Norman (1958), and later modified by Tonari et al (1970) to give enhanced yields. The sequence is illustrated in Scheme V. Although the overall yield was originally quite modest (~15%), the synthesis employs inexpensive readily available chemicals and does not require alkylation with an alkyl halide.…”

Section: Synthetic Routesmentioning

confidence: 99%

See 1 more Smart Citation

Synthetic routes to 2-hydroxy-3-methylcyclopent-2-en-1-one and related cyclopentane-1,2-diones: a review

Strunz¹

1983

J. Agric. Food Chem.

View full text Add to dashboard Cite

Section: Synthetic Routesmentioning

confidence: 99%

“…It was conducted as far as 13 without isolation of intermediates. The modified experimental conditions developed by Tonari et al (1970) increased the overall yield to 44%.…”

Section: Synthetic Routesmentioning

confidence: 99%

Synthetic routes to 2-hydroxy-3-methylcyclopent-2-en-1-one and related cyclopentane-1,2-diones: a review

Strunz¹

1983

J. Agric. Food Chem.

View full text Add to dashboard Cite

“…hydroxy-2-cyclopentenone, 3) and 3,5-dimethyl-2-hydroxy- 2-cyclopentenone4'5) all having a sweet and caramel-like odor.…”

mentioning

confidence: 99%

Synthesis of 5-alkyl-5-methyl-2-hydroxy-2-cyclopentenones.

Naoshima

Makita

Kondo

et al. 1982

Agricultural and Biological Chemistry

View full text Add to dashboard Cite

Cyclotene (1) and its related compounds, enolizable alkyl cyclic 1,2-diketones, are important flavoring materials in roasted coffee. 1 } Specifically, considerable interest exists in the synthesis of cyclotene (1),2~4) 3-ethyl-2-hydroxy-2-cyclopentenone,3) and 3,5-dimethyl-2-hydroxy-2-cyclopentenone4'5) all having a sweet and caramel-like odor.In the preceding report, an attempt was made to synthesize 5,5-dialkyl-2-hydroxy-2-cyclopentenones using the alkylation of a cyclotene 1,3-dithiane derivative.6) We describe in this paper a successful method for synthesizing 5-alkyl-5-methyl-2-hydroxy-2-cyclopentenones and their flavor properties.Cyclotene monoketal derivative 2,7) easily prepared in three steps from 1, was alkylated with methyl iodide and sodium hydride in refluxing THFto give the methylated ketal 3a in a 68% yield. Whenthis methylation was carried out with the addition of 18-crown-6, an 80% yield of 3a could be obtained. Similarly, 2 was treated with ethyl iodide, «-propyl bromide and allyl bromide in the presence of 18-crown-6 to afford the corresponding alkylated ketals, 3b, 3c, and 3d, in a yield of 65%, 21% and 89%, respectively. Alkylated monoketal ketones, 3a -3d, were heated with 10% sulfuric acid to give the enolizable fivemembered ring 1,2-diketones, 4a-4d, in a yield of 55-80%..The 5,5-dimethyl diketone 4a had a burnt caramel-like odor, while the 5-ethyl-5-methyl and 5-«-propyl-5-methyl diketones, 4b and 4c, showed a weak caramel-like odor.The 5-allyl-5-methyl diketone 4d possessed a sweet odor with minty overtones. EXPERI MENTALAll melting points and boiling points were uncorrected. IR spectra were measured with a Hitachi 260-10 spectrometer. *H NMRspectra were obtained in CDC13solu-tions on a Hitachi R-24B spectrometer using Me4Sias an internal standard. 13C NMRspectra were taken in CDC13solutions. Mass spectra were determined on a JEOL JMS-D300 spectrometer under electron impact (El, 70 eV) and chemical ionization (CI, 200 eV, isobutane).Columnchromatographies were carried out with Merck 70-230 mesh silica gel.General procedure for alkylation. A solution of 2 (8.5 g, 0.05 mol) in dry THF (10ml) was added dropwise, under N2, to a mixed solution ofNaH (2.88g ofa 50% mineral oil dispersion, 0.06mol) and 18-crown-6 (1.32 g, 0.005 mol) in dry THF (20ml) with stirring at room temperature and stirring was continued for 1 hr. To the solution was added alkyl halide (0.06 mol) and the mixture was refluxed with stirring. The reaction mixture was cooled and worked up in the usual manner. The crude product thus obtained was purified by column chromatography with hexane-ether.

show abstract

Heterocycles structurally influenced by a side chain. X. Effect of temperature and side chain on the imine‐enamine tautomerism in the quinoxalinone and pyridopyrazinone systems

Seki

Iwanami

Kuwatani

et al. 1997

Journal of Heterocyclic Chem

View full text Add to dashboard Cite

3‐(1‐Benzoyl)ethyl‐1H‐pyrido[2,3‐b]pyrazin‐2‐one (7), 3‐(1‐ethoxycarbonyl)ethyl‐1H‐pyrido[2,3‐b]‐pyrazin‐2‐one (8), and 3‐(1‐benzoyl)ethyl‐1H‐quinoxalin‐2‐one (9) exist only in the imine form due to the steric effect of the methyl substituent. As regards the imine‐enamine tautomerism, 3‐(β‐carbonylmethylene) derivatives of 1,2‐dihydro‐4H‐pyrido[2,3‐b]pyrazin‐3‐one such as 12 and 15–18 gradually change from the enamine form to the imine form with elevated temperatures; however, 3‐(carbonylmethylene) derivatives of 3,4‐dihydro‐1H‐pyrido[2,3‐b]pyrazin‐2‐one such as 10, 19 and 20 show little temperature effect. 2‐Phenacylidene‐1,2‐dihydro‐4H‐pyrido[3,4‐b]pyrazin‐3‐one (21) and 3‐phenacylidene‐3,4‐dihydro‐1H‐pyrido[3,4‐b]pyrazin‐2‐one (22), which exist in the enamine form, show no temperature effect.

show abstract

Syntheses of Cyclotene and Its Related Compounds

Cited by 3 publications

References 0 publications

Synthetic routes to 2-hydroxy-3-methylcyclopent-2-en-1-one and related cyclopentane-1,2-diones: a review

Synthetic routes to 2-hydroxy-3-methylcyclopent-2-en-1-one and related cyclopentane-1,2-diones: a review

Synthesis of 5-alkyl-5-methyl-2-hydroxy-2-cyclopentenones.

Heterocycles structurally influenced by a side chain. X. Effect of temperature and side chain on the imine‐enamine tautomerism in the quinoxalinone and pyridopyrazinone systems

Contact Info

Product

Resources

About