- Oxyallyl Cation Capture via Electrophilic Deborylation of Organoboronates: Access to α, α′-Substituted Cyclic Ketones
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An umpolung strategy to synthesize α,α′-substituted cyclic ketones through the nucleophilic addition of organoboronates to α-hydroxyl silyl enol ethers is described. The reaction proceeds via the trapping of in situ generated oxyallyl cations via the electrophilic deborylation of C(sp2) and C(sp) borates. This efficient and straightforward method provides direct access to α-substituted silyl enol ethers in high yield with complete regioselectivity. Desilylation in a one-pot procedure provides the corresponding α,α′-disubstituted ketones with high diastereoselectivity.
- Nguyen, Truong N.,Setthakarn, Krit,May, Jeremy A.
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supporting information
p. 7837 - 7840
(2019/10/16)
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- Imidazole derivative used as antiviral agent and use thereof in preparation of medicament
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Disclosed are an antiviral compound and a use thereof in the preparation of a medicament for the treatment of virus infections. Specifically, the present invention relates an imidazole derivative for treating respiratory syncytial virus infection.
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- Heterogeneous platinum catalytic aerobic oxidation of cyclopentane-1,2- diols to cyclopentane-1,2-diones
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A method for the aerobic oxidation of cyclopentane-1,2-diols to the corresponding diketones over a commercial heterogeneous Pt/C catalyst is described. Unsubstituted and 3- or 4-substituted cyclopentane-1,2-diols are oxidized to 1,2-dicarbonyl compounds in good yields under the reported optimized reaction conditions (atmospheric air, 1 mol % of catalyst, 1 equiv of LiOH, aqueous solvents and 60 °C temperature). The method is applicable for producing cyclopentane-1,2-diketones in a scalable manner.
- Reile, Indrek,Kalle, Sigrid,Werner, Franz,J?rving, Ivar,Kudrjashova, Marina,Paju, Anne,Lopp, Margus
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p. 3608 - 3613
(2014/05/20)
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- Asymmetric synthesis of chiral 1,3-diaminopropanols: Bisoxazolidine- catalyzed C-C bond formation with α-keto amides
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Three high-yielding steps lead to the formation of chiral 1,3-diaminopropanols from aliphatic and aromatic α-keto amides. In this approach, a nitroaldol reaction, which is catalyzed by Cu(SO2CF 3)2 and the bisoxazolidine ligand L1, is followed by two mild reduction reactions (see scheme). Laborious protection and deprotection steps can be avoided by using this method.
- Xu, Hanhui,Wolf, Christian
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p. 12249 - 12252
(2012/02/01)
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- Thermal decomposition of ascorbic acid
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Thermal degradation of L-ascorbic acid at 300 °C in the absence of a solvent yielded mostly furan derivatives and α,β-unsaturated cyclic ketones with a five-membered ring. Some of the furan derivatives are the same as those obtained in the Maillard reaction, with the reductones undergoing retroaldol reaction, decarboxylation, oxidation, and hydrolysis. In propylene glycol, under milder conditions (180 °C), the carbonyl and dicarbonyl derivatives resulting from the decomposition react with the solvent and give cyclic acetals and ketals (1,3-dioxolanes). The products were identified by GC-MS using the SPECMA data bank.
- Vernin, Gaston,Chakib, Soundouss,Rogacheva, Sonia M.,Obretenov, Tzvetan D.,Parkanyi, Cyril
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- Novel Products in the Weiss Reaction of 1,2-Cyclopentanedione. Improved Preparation of Propellane-3,7-dione
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The reaction of 1,2-cyclopentanedione (1c,9) with the 3-oxoglutarate 4 in methanol/water in the presence of sodium bicarbonate followed by hydrolysis and decarboxylation of the product mixture affords the oxapropellane ester 11c in addition to the propellanedione 6c.The alkali enolates of 4 react with 9 in boiling methanol to yield the yellow, poorly soluble alkali dihydropentalenolates 12M and the propellane tetraester 5c, which on hydrolysis and decarboxylation yields 53percent of 6c.The dihydropentalenol 12H equilibrates with the tautomeric β-oxodiester 13, the proportion of which increases with solvent polarity.In methanol solutions, 12H and 13 add diastereoselctively forming the dicyclopenta-s-indacene tetraester syn-14, which is derived from a novel pentacyclic ring system.The configuration of syn-14 is determined by X-ray diffraction analysis.The mechanisms of formation are discussed for 11c, 12M, and syn-14. - Keywords: Dicyclopenta-2-indacene/ 2-Oxapropellane derivatives/ Pentalene derivatives/ Propellane-3,7-dione/ Weiss reaction
- Quast, Helmut,Roeschert, Horst,Peters, Eva-Maria,Peters, Karl,Schnering, Hans Georg von
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p. 523 - 532
(2007/10/02)
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- Anhydrous Iron(III) Chloride Dispersed on Silica Gel; III. A Convenient and Mild Reagent for Deacetalization in Dry Medium
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Acetals of various structures are conveniently cleaved under mild conditions by anhydrous iron(III) chloride dispersed on silica gel in the absence of any solvent.
- Fadel, Antoine,Yefsah, Ramdane,Salauen, Jacques
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- Tobacco smoke chemistry. 1. A chemical and mass spectrometric study of tobacco smoke alkyl 2-hydroxy-2-cyclopentenones.
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A series of alkyl 2-hydroxy-2-cyclopentenones, which comprise biologically and organoleptically active compounds, have been synthesized and subjected to high resolution mass spectrometric studies to clarify structurally significant fragmentation pathways. On the basis of these results, 26 alkyl 2-hydroxy-2-cyclopentenones were identified in the weakly acidic fraction of smoke condensate from American blend type cigarettes, eighteen of which had not been detected in tobacco smoke previously. The utility for identification purposes of the corresponding quinoxaline derivatives, obtained through condensation with o-phenylenediamine, is discussed.
- Arnarp,Enzell,Petersson,Pettersson
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p. 839 - 854
(2007/10/02)
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