- Organocatalyzed asymmetric synthesis of morphans
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A general effective organocatalyzed synthesis of enantioenriched morphans with up to 92% ee was developed. The morphan scaffold was constructed in a one-pot tandem asymmetric organocatalyzed Michael addition followed by a domino Robinson annulation/aza-Michael intramolecular reaction sequence from easily available starting materials.
- Bradshaw, Ben,Parra, Claudio,Bonjoch, Josep
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supporting information
p. 2458 - 2461
(2013/06/27)
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- A stereoselective and practical synthesis of (E)-α,β-unsaturated ketones from aldehydes
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α,β-Unsaturated ketones can be prepared by reaction of differently substituted β-keto acids and aldehydes. The reaction is carried out under organocatalysis (β-alanine, 0.5 equiv.) and generates the enones with high E selectivity (>95%). This version of the Verley-Doebner modification of the Knoevenagel reaction is a practical alternative to the classic Horner-Wadsworth-Emmons (HWE) reaction without the formation of high molecular weight byproducts. The process makes use of simple reagents and can be applied to large-scale synthesis under conditions compatible with atom-economy principles. Differently substituted aliphatic, aromatic, or heteroaromatic α,β-unsaturated ketones can be prepared. An example of a hydroformylation/Verley-Doebner Knoevenagel telescoped process is also described. The conditions used in the Knoevenagel reaction to prepare conjugated esters under amino acid organocatalysis can be applied also for the synthesis of α,β unsaturatedketones. β-Keto acids are prepared byhydrogenolysis of the corresponding benzyl ester and react easily with aldehydes to give the α,β-unsaturated ketones without formation of high molecular weight byproducts. Copyright
- Balducci, Evita,Attolino, Emanuele,Taddei, Maurizio
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experimental part
p. 311 - 318
(2011/02/28)
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- FLUORESCENT LANTHANIDE COMPLEX
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A luminescent lanthanide complex using a photo induced electron transfer as the luminescence controlling principle is presented. The complex comprises a substituted 2-quinolinol containing a sensor group and a complex group and lanthanide ion (Ln3+). This complex is allowed to be co-present in a liquid phase with a material to be measured, and the luminescence of said complex is measured.
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Page/Page column 8
(2008/06/13)
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- Small molecule inhibitors of bacterial quorum sensing and biofilm formation
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Bacteria monitor their local population densities using small molecules (or autoinducers) in a process known as quorum sensing. Here, we report a new and efficient synthetic route to naturally occurring bacterial autoinducers [N-acyl L-homoserine lactones (AHLs)] that is readily amenable to the synthesis of analogues. This route has been applied in the first synthesis of a library of non-native AHLs. Evaluation of these compounds in bacterial reporter gene and biofilm assays has revealed a potent set of quorum sensing antagonists. These ligands will serve as valuable new tools to explore the role of quorum sensing in bacterial pathogenesis. Copyright
- Geske, Grant D.,Wezeman, Rachel J.,Siegel, Adam P.,Blackwell, Helen E.
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p. 12762 - 12763
(2007/10/03)
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- The reaction of β-ketoacids with allylboronates
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Allylboronates react with β-ketoacids to yield tertiary homoallylic β-hydroxycarboxylic acids. The reaction presumably proceeds via a bicyclic transition state. The β-carboxylic substituent enhances the rate of the reaction.
- Kabalka,Yang,Wang
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p. 511 - 517
(2007/10/03)
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- Electrocarboxylation de composes carbonyles aliphatiques, aromatiques et vinyliques: interet de l'utilisation d'une anode consommable en magnesium
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In the presence of carbon dioxide in DMF, the electroreduction of carbonyl compounds or α,β-ketoalkenes at high concentration yields respectively α-hydroxyacids and β-ketoacids.The use of a sacrificial magnesium anode allows constant current electrolyses in a diaphragmless cell.
- Mcharek, Slah,Heintz, Monique,Troupel, Michel,Perichon, Jacques
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- Knoevenagel Reactions with β-Oxo Acids. Regiospecific Enol Equivalents for Syntheses of α,β-Unsaturated Ketones and of Some β-Ketols
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3-Oxobutanoic acid reacts with aliphatic aldehydes in the presence of pyridine to give α,β-unsaturated methyl ketones in good yields.Analogous results were obtained with a series of other β-oxo acids.Synthesis of (E)-7-methyloct-4-en-3-one, a major constituent of the marine sponge Plakortis zygompha, has been carried out using this methodology.Aromatic aldehydes are generally less reactive under these conditions but give β-ketols when the phenyl ring bears an electron-withdrawing substituent.Some observations on the mechanism of the reaction between 3-oxobutanoic acid and benzaldehyde are presented.
- Grayson, David H.,Tuite, Mathew R. J.
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p. 2137 - 2142
(2007/10/02)
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- An Improved Synthesis of 1,4-Benzo- and 1,4-Naphthoquinones Bearing Active Substituents
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The synthesis of 1,4-benzoquinones and 1,4-naphthoquinones 3a-j carrying substituents such as methoxyl, allyl or oxiranyl was substantially improved.The 1-methoxy-4-methoxymethyloxy 2a-d, g-k or 1,4-bis(methoxymethyloxy) derivatives 2e-f were used, as a substrates instead of 1,4-dimethoxy derivatives 1a-j hitherto used and they were oxidized with silver(II) dipicolinate.Among numerous examples, the synthesis of a new analog of ubiquinone 3d with the oxiranyl substituent, being a new bioactivated alkylating agent, is reported.
- Syper, Ludwik,Kloc, Krystian,Mlochowski, Jacek
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p. 808 - 822
(2007/10/02)
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