A General Synthesis of 2-Methoxy-2-Cyclohexenones

Wenkert, Ernest; Golob, Norman F.; Sathe, S. S.; Smith, R. A. J.

doi:10.1080/00397917308062037

Cited by 19 publications

(7 citation statements)

References 5 publications

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“…It was interesting to note that they isolated only the racemic epoxylactone 10 in 80% yield, but as a single diastereomer. Wipf and coworkers 379 also examined additional substrates, including ve-and six-membered diosphenol ethers (11 380,381 and 13 382 ), and the highly functionalized hydroxy enol ether 15. An epoxide (as found in 9) was clearly not necessary since enone 11 underwent an oxidative rearrangement to afford lactone 12 in 75% yield (Scheme 33).…”

Section: Oxidative Rearrangement Of Cyclic Enol Ethers To Aalkoxyestersmentioning

confidence: 99%

meta-Chloroperbenzoic acid (mCPBA): a versatile reagent in organic synthesis

et al. 2014

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Section: Oxidative Rearrangement Of Cyclic Enol Ethers To Aalkoxyestersmentioning

confidence: 99%

meta-Chloroperbenzoic acid (mCPBA): a versatile reagent in organic synthesis

et al. 2014

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“…Enones 9a/c were prepared by literature methods . Because of their largely routine nature, experimental details for the preparation of 6 , 7a/b , and 8a/b are included in the Supporting Information.…”

Section: Experimental Sectionmentioning

confidence: 99%

Studies on the Synthesis of Acanthodoral and Nanaimoal: Evaluation of Cationic Cyclization Routes

1996

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Intramolecular Lewis acid-promoted reactions of α,β-unsaturated ketone 6 and aldehydes 7 and 8 were examined as potential routes to acanthodoral (1), a structurally interesting natural product. Ketone 6 afforded ene product 22 exclusively, and both 7 and 8 gave mixtures of bicyclic aldehydes 3 and 26 and tricyclic aldehyde 25. The latter most likely results from 7 by intramolecular cyclization of the alkene onto the Lewis acid-activated carbonyl moiety affording carbocation 31 followed by a 1,2-hydride shift and ring closure. Starting from 8, tricyclic aldehyde 25 apparently forms by cyclization to cation 35 and ring closure to cyclobutane 36, followed by ring opening to 31, the same cation as formed in reactions of 7. Nanaimoal (3) results from loss of H+ from 31, and bicyclic aldehyde 26 may be formed in a similar manner or by a concerted ene reaction. The configuration of 25 establishes that the stereochemistry of the initial cyclization to 31 precludes the possible use of this strategy for the synthesis of acanthodoral. However, acid-promoted cyclization of allylic alcohol 23 efficiently gives diene 29 which undergoes selective hydroboration/oxidation to afford nanaimoal.

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“…In the first synthesis, we prepared 4-isopropyl-2-methoxy-2-cyclohexen-1-one (3) by the annelation method of Wenkert [2], and found the yields were poor, in accord with other workers [3]. We used the morpholine enamine 4 in place of the more expensive pyrrolidine enamine.…”

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confidence: 84%

Homologues of p‐Menthane Derivatives in Roman Camomile

Thomas

Schouwey

Egger

1981

Helvetica Chimica Acta

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Summary 5-Isopropyl-2-propyl-2-cyclohexen-l-one (1) and 5-isopropyl-2-(2-methylpropyl)-2-cyclohexen-1-one (2), homologues of the p-methene ketone carvotanacetone, have been identified in the oil of Anthemis nobilis. Their synthesis involved allylation of a cyclohexane-1,3-dione, and the acid-catalyzed cyclization to dihydrofurans of the 2-allylcyclohexane-l,3-diones is described. The stereochemistry of metal hydride reduction of 3-ethoxy-5-isopropyl-2-propyl-2-cyclohexen-1 -one (18) is mentioned in the course of the synthesis of the natural products. Some biogenetic considerations are discussed.In the course of an analysis of the oil of Roman camomile (Anthemis nobilis), the two ketones, 1 and 2, were isolated'). Because very small amounts were available from natural sources, we carried out syntheses of the racemates.In the first synthesis, we prepared 4-isopropyl-2-methoxy-2-cyclohexen-1-one (3) by the annelation method of Wenkert [2], and found the yields were poor, in accord with other workers [3]. We used the morpholine enamine 4 in place of the more expensive pyrrolidine enamine. The major difficulty of the route was in scale-up; while the removal of methanol from 1,4-dimethoxy-2-butanone (5) with p-toluenesulfonic acid runs well on the small scale described [2] [3], larger amounts tend to polymerize during the preparation. More rapid distillation results in lower yields, but the resulting mixture of 5 with the vinyl ketone 6 can be used as such in the cyclization to 3.Reaction of propylmagnesium bromide in ether on 3 yielded the corresponding tertiary alcohol 7, mostly in a single configuration which, we feel, must be the isomer having both alkyl substituents on the same side of the ring, based on the 'axial-attack' model for Grignard additions [4]. Treatment of the crude mixture of these alcohols with p-toluenesulfonic acid in refluxing toluene led to a 7: 1 -

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A General Synthesis of 2-Methoxy-2-Cyclohexenones

Cited by 19 publications

References 5 publications

meta-Chloroperbenzoic acid (mCPBA): a versatile reagent in organic synthesis

meta-Chloroperbenzoic acid (mCPBA): a versatile reagent in organic synthesis

Studies on the Synthesis of Acanthodoral and Nanaimoal: Evaluation of Cationic Cyclization Routes

Homologues of p‐Menthane Derivatives in Roman Camomile

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