Base-induced rearrangements of .alpha.-epoxy ketones

Treves, Gino R.; Stange, Hugo; Olofson, R. A.

doi:10.1021/ja01000a047

Cited by 9 publications

(6 citation statements)

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“…Hence, more carboxylic acids must be generated by transformation of other functional groups during the reduction process in order to account for all of the CO 2 generated. Route 2 shows a possible epoxide–carbonyl to carboxylic acid transformation; this is also known as α-epoxy ketone rearrangement that occurs in benzylic acids . The ring opening of epoxides is acid or base catalyzed and is favored in hydrothermal conditions due to the increased self-ionization of water at elevated temperatures .…”

Section: Discussionmentioning

confidence: 99%

“…Route 2 shows a possible epoxide−carbonyl to carboxylic acid transformation; this is also known as α-epoxy ketone rearrangement that occurs in benzylic acids. 48 The ring opening of epoxides is acid or base catalyzed and is favored in hydrothermal conditions due to the increased self-ionization of water at elevated temperatures. 49 As a result, diols are formed; these can rearrange along with a closeby ketone present on an α-carbon, forming a carboxylic acid that can then decompose to give CO 2 .…”

Section: ■ Discussionmentioning

confidence: 99%

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Understanding Hydrothermally Reduced Graphene Oxide Hydrogels: From Reaction Products to Hydrogel Properties

et al. 2016

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We studied the chemical processes that take place during hydrothermal gelation of graphene oxide (GO), quantifying the reaction products generated during hydrothermal reduction. The gelation proceeds with disproportionation of GO yielding a large amount of CO2 (about a quarter of the original mass of GO), organic acidic fragments, and CO. The CO2 that is formed is trapped in the hydrogel creating macroscopic voids which can lead to cracking of the hydrogel during compression. We were able to quantify the amount of CO2 produced in situ by adding ammonia during the synthesis, and converting CO2 into ionic carbonate species that we could easily quantify by titration. We used titration to evaluate the formation of organic acidic fragments too and evaluated the amount of H2O and CO produced by thermogravimetric analysis and mass balance. The conversion of CO2 into ionic species allowed us to produce void-free hydrogels which remain structurally stable after extensive compression. However, such hydrogels on average showed lower mechanical strength and electrical conductivity than the hydrogels with voids. This is a result of the difference in chemistry and morphology between hydrogels reduced under acidic pH and basic pH. Our work provides for the first time a clear quantitative estimate of CO2 evolution and organic fragment formation during hydrothermal reduction of GO, an overall picture of the reaction products, and a deepened understanding of the conditions that can be used to prepare stronger and more conductive graphene hydrogels and aerogels.

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Section: Discussionmentioning

confidence: 99%

Section: ■ Discussionmentioning

confidence: 99%

Understanding Hydrothermally Reduced Graphene Oxide Hydrogels: From Reaction Products to Hydrogel Properties

et al. 2016

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“…Procedure B: 678 mg, 97% yield; colorless oil; 1 H NMR (400 MHz, CDCl 3 ) δ 8.01 (d, J = 7.5 Hz, 2H), 7.62 (t, J = 7.3 Hz, 1H), 7.50 (t, J = 7.5 Hz, 2H), 4.04 (s, 1H), 3.08 (d, J = 6.4 Hz, 1H), 2.10–2.00 (m, 1H), 1.91–1.82 (m, 2H), 1.69–1.45 (d, 6H); 13 C NMR (151 MHz, CDCl 3 ) δ 194.7, 135.6, 133.8, 128.8, 128.2, 63.2, 57.0, 41.4, 29.1, 28.8, 25.4. Product 3p is a known compound …”

Section: Methodsmentioning

confidence: 99%

Darzens Reaction Rate Enhancement Using Aqueous Media Leading to a High Level of Kinetically Controlled Diastereoselective Synthesis of Steroidal Epoxyketones

2014

J. Org. Chem.

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Darzens reactions between halocarbonyls and aldehydes have been carried out in water in the presence of a Li(+)-containing base, a phase-transfer catalyst, and granular polytetrafluoroethylene under mechanical stirring. Reactions using both aromatic and aliphatic aldehydes produced epoxides stereoselectively in good to excellent yields. This is the first time that aliphatic aldehydes with α-H have been used in aqueous Darzens reactions. The Darzens reactions were much faster in water than in organic solvents. This aqueous rate enhancement occurred for Darzens reactions between enantiopure steroidal haloketones and aldehydes, yielding enantiopure spiroepoxides with a high level of kinetically controlled diastereoselectivity. Chromatography was avoided in the purifications of the steroidal spiroepoxides. This is an example of preparing enantiopure epoxyketones via aqueous Darzens reaction using chiral α-haloketone substrates.

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“…Magnesium homo-enolates were also prepared by this approach. Thus, the reaction of the β-iodoester 8a with i Pr 2 Mg·LiCl ( 3 ) at −10 °C led to the corresponding magnesium homo-enolate, which reacted with benzaldehyde leading after lactonization to the spirolactone 10a in 68% yield (entry 1, Table ) . Its reaction with allyl bromide provided the corresponding allylated product 10b in 78% yield (entry 2) …”

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confidence: 99%

“…Thus, the reaction of the β-iodoester 8a with iPr 2 -Mg‚LiCl (3) at -10 °C led to the corresponding magnesium homo-enolate, which reacted with benzaldehyde leading after lactonization to the spirolactone 10a in 68% yield (entry 1, Table 2). 13 Its reaction with allyl bromide provided the corresponding allylated product 10b in 78% yield (entry 2). 14 The same conditions gave, with carboxylic ester 8b, the allylated product 10c in 68% yield (entry 3).…”

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confidence: 99%