Five membered ring formation of 2-hydroxyalkyl malonate and acetoacetate derivatives the problem of O-versus C-alkylation

Adams, Elisabeth; Hiegemann, Monika; Duddeck, H.; Welzel, Peter

doi:10.1016/s0040-4020(01)87922-9

Cited by 17 publications

(5 citation statements)

References 53 publications

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“…We first synthesized the phosphate trismalonate 8 involving three ethano spacers in a two‐step procedure (Scheme ), which is considerably more efficient than that of benzene‐based trismalonate tethers. Ethylene glycol was esterified with methyl malonyl chloride according to a literature procedure 9. The corresponding methyl malonyl alkanol 3 was then converted into trismalonate 8 .…”

Section: Methodsmentioning

confidence: 99%

Invertomers of Fullerenophosphates

et al. 2013

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Section: Methodsmentioning

confidence: 99%

Invertomers of Fullerenophosphates

et al. 2013

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“…Indeed, controlling the selectivity of C vs. O alkylation is a general problem in the reaction of electrophiles with enolates derived from 1,3-dicarbonyl compounds. 37 For intermolecular alkylation reactions, C -alkylation can often be favored by choosing an appropriate solvent, counterion, or leaving group. However, the corresponding intramolecular alkylation reactions are often controlled by stereoelectronic effects and strongly favor O -alkylation regardless of the reaction conditions.…”

Section: Resultsmentioning

confidence: 99%

“…Similarly, when the alkylation reaction was run in the presence of chelating Lewis acids, acylketene acetal 45 was still the only isolable product. Indeed, controlling the selectivity of C- versus O-alkylation is a general problem in the reaction of electrophiles with enolates derived from 1,3-dicarbonyl compounds . For inter molecular alkylation reactions, C-alkylation can often be favored by choosing an appropriate solvent, counterion, or leaving group.…”

Section: Resultsmentioning

confidence: 99%

“…After warming to room temperature, the organic layer was isolated, and the aqueous phase was extracted with one additional portion of CH 2 Cl 2 . The combined organics were dried over anhydrous Na 2 SO 4 before removal of the solvent under reduced pressure and purification of the residue by column chromatography ( (37). To a flask containing solid 10% palladium on carbon (150 mg, 0.14 mmol, 0.25 equiv) was added a solution of protected diol 36 (298 mg, 0.57 mmol, 1.00 equiv) in 10 mL of anhydrous methanol and 5 mL of EtOAc.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

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Toward a Synthesis of Hirsutellone B by the Concept of Double Cyclization

et al. 2013

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This account describes a strategy for directly forming three of the six rings found in the polyketide natural product hirsutellone B via a novel cyclization cascade. The key step in our approach comprises two transformations: a large-ring forming, nucleophilic capture of a transient acyl ketene and an intramolecular Diels–Alder reaction, both of which occur in tandem through thermolyses of appropriately functionalized, polyunsaturated dioxinones. These thermally induced “double cyclization” cascades generate three new bonds, four contiguous stereocenters, and a significant fraction of the polycyclic architecture of hirsutellone B. The advanced macrolactam and macrolactone intermediates that were synthesized by this process possess key features of the hirsutellone framework, including the stereochemically dense decahydrofluorene core and the strained para-cyclophane ring. However, attempts to complete the carbon skeleton of hirsutellone B via transannular carbon-carbon bond formation were undermined by competitive O-alkylation reactions. This account also documents how we adapted to this undesired outcome through an evaluation of several distinct strategies for synthesis, as well as our eventual achievement of a formal total synthesis of hirsutellone B.

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“…The reaction mixture was heated at reflux or at 60°C and monitored by GC-MS. When the starting material had disappeared ( [14] TBDPSO(CH 2 ) 5 OH, [15] BnO(CH 2 ) 5 OH, [16] TrO(CH 2 ) 5 OH, [17] and 2-PMBO-cyclohexanone [18] were identified by comparison with literature data.…”

Section: Resultsmentioning

confidence: 99%

Cerium(III) Triflate versus Cerium(III) Chloride: Anion Dependence of Lewis Acid Behavior in the Deprotection of PMB Ethers

Bartoli¹,

Dalpozzo²,

Nino³

et al. 2004

Eur J Org Chem

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Cerium(III) triflate deprotects p‐methoxybenzyl ethers of simple alcohols better than the cerium(III) chloride/sodium iodide system. It can be used in 1% M instead of equimolecular amounts, giving better yields. Aromatic alcohols rearrange, but the addition of a scavenger overcomes this drawback. Unfortunately, unsaturated alcohols are deprotected with decomposition, probably due to side electrophilic additions to double bonds. A comparison between the mechanisms of cerium triflate and cerium chloride is reported. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

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Five membered ring formation of 2-hydroxyalkyl malonate and acetoacetate derivatives the problem of O-versus C-alkylation

Cited by 17 publications

References 53 publications

Invertomers of Fullerenophosphates

Invertomers of Fullerenophosphates

Toward a Synthesis of Hirsutellone B by the Concept of Double Cyclization

Cerium(III) Triflate versus Cerium(III) Chloride: Anion Dependence of Lewis Acid Behavior in the Deprotection of PMB Ethers

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