- Poly substituted 5-functionalized 2-pyrone derivatives: Facile synthesis via tandem nucleophilic addition/lactonization reaction of 1,2-allenyl esters
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Polysubstituted 5-functionalized 2-pyrone derivatives were synthesized via the K2CO3-catalyzed reaction of 1,2-allenyl esters and α-substituted ketones with electron-withdrawing groups through a tandem nucleophilic addition/lactonization process. Georg Thieme Verlag Stuttgart.
- Huang, Xian,Shen, Ruwei
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Read Online
- Catalytic asymmetric tamura cycloadditions
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In the presence of a novel, tert-butyl-substituted squaramide-based catalyst, enolizable anhydrides react with alkylidene oxindoles to generate spirooxindole products of significant synthetic interest with excellent enantio- and diastereocontrol. The methodology is of wide scope and encompasses both homophthalic and glutaconic anhydride derivatives, which lead to structurally diverse products. Glutaconic acid-derived anhydrides undergo a clean post-cyclization decarboxylation process which is not a feature of reactions involving homophthalic acid-derived anhydrides. The unusual influence of reaction temperature on diastereocontrol has been probed, with reactions occurring at 30 °C and -30 °C delivering products epimeric at one stereocenter only, in near optical purity. Squared away: The first strategy for bringing about enantioselective Tamura reactions is reported. In the presence of a squaramide-based catalyst, enolizable anhydrides react with alkylidene oxindoles to generate spirooxindole products with excellent enantio- and diastereocontrol. The methodology is of wide scope and leads to structurally diverse products.
- Manoni, Francesco,Connon, Stephen J.
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supporting information
p. 2628 - 2632
(2014/03/21)
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- Synthesis of some C2-symmetric bidentate ligands and their complexes derived from Feist's acid
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Various new C2-symmetric bidentate ligands, bearing phosphorus, nitrogen, and sulfur, were obtained in an efficient manner, starting from (±)-trans-3-methylidenecyclopropane-1,2-dicarboxylic acid (Feist's acid; (±)-trans-3). The structures of the new bidentate ligands, di(tert-butyl) (±)-[(trans-3-methylidenecyclopropane-1,2-diyl)dimethanediyl] biscarbamate ((±)-9), (±)-(trans-3-methyldienecyclopropane-1,2- diyl)dimethanaminium dichloride ((±)-10), (±)-S,S′-[(trans- 3-methylidenecyclopropane-1,2-diyl)dimethanediyl] diethanethioate ((±)-11), and (±)-[(trans-3-methylidenecyclopropane-1,2-diyl) dimethanediyl]bis(diphenylphosphane) ((±)-12), were fully characterized by standard spectroscopic techniques. These new classes of C2- symmetric bidentate ligands have the potential to be used in asymmetric catalysis. Copyright
- Al-Majid, Abdullah M. A.,Al-Othman, Zeid A.,Islam, Mohammad Shahidul
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experimental part
p. 268 - 277
(2012/04/10)
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- MECANISMO DE LA REACCION DE COMPUESTOS 1,3-DICARBONILICOS CON ANHIDRIDO TRIFLICO. CICLACION ANOMALA DEL ESTER ACETILACETICO A 3-ETOXICARBONIL-2,6-DIMETIL-4-PIRONA.
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The reaction of ethyl acetoacetate (1) with triflic anhydride (Tf2O) in excess, in the presence of nitriles (3) affords 3-ethoxycarbonyl-2,6-dimethyl-4-pyrone (10), instead of 5-ethoxycarbonyl-4,6-dimethyl-2-pyrone (5), which is the usual product formed in the cyclization of 1 catalyzed by protic or Lewis acids.Palabras clave: 2-pirona, 4-pirona, anhidrido triflico, ester acetylacetico.
- Martinez, A. Garcia,Fernandez, A. Herrera,Vilchez, D. Molero,Ubeda, A Herrera,Hanack, M.,Subramian, L. R.
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p. 121 - 123
(2007/10/02)
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- Extractives from New Zealand Honeys. 5. Aliphatic Dicarboxylic Acids in New Zealand Rewarewa (Knightea excelsa) Honey
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Thirty-two aliphatic dicarboxylic acids were identified as methyl esters in the methylated diethyl ether extracts of four unifloral grade New Zealand rewarewa (Knightea excelsa) honeys using combined gas chromatography-mass spectrometry (GC-MS). 2-Methoxybutanedioic acid (O-methylmalic acid) and 4-hydroxy-3-methyl-trans-2-pentenedioic acid are proposed as floral marker substances for New Zealand rewarewa honey.The total level of aliphatic dicarboxylic acids identified in the rewarewa honey samples ranged from 64 to 111 mg/kg, with an average level of 88 mg/kg.Keywords: Rewarewa (Knightea excelsa) honey; aliphatic dicarboxylic acids; 2-methoxybutanedioic acid; 4-hydroxy-3-methyl-trans-2-pentenedioic acid
- Wilkins, Alistair L.,Lu, Yinrong,Tan, Seng-To
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p. 3021 - 3025
(2007/10/03)
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- An improved synthesis of a mixture of diethyl (Z)- and (E)-3-methylglutaconates from ethyl acetoacetate
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A simple, efficient two-step synthesis of a mixture of diethyl (Z)- and (E)-3-methylglutaconates from isodehydroacetic acid in 83% yield is described. On the basis of this synthesis an improved procedure for the preparation of a mixture of (Z)- and (E)-3-methylglutaconic acids from ethyl acetoacetate in 44% overall yield was elaborated.
- Kuchkova,Morari,Vlad
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p. 1221 - 1222
(2007/10/02)
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- A Stereospecific Synthesis of (+/-)-Abscisic Acid
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A convenient separation of (E)- and (Z)-3-methylpent-2-enedioic acids was devised, and it was shown that with acetyl chloride or thionyl chloride the (Z)-acid yields the cyclic anhydride while the (E)-acid forms 6-chloro-4-methylpyran-2-one.The chloropyranone by conventional chemistry gave 4-methyl-6-(2'-oxopropyl)pyran-2-one which condensed with 4-methylpent-3-en-2-one in the presence of pyrrolidine, yielding 4-methyl-6-(2',6',6'-trimethyl-4'-oxocyclohex-2'-enyl)pyran-2-one.Oxidation with selenium dioxide or t-butyl chromate then gave 6-(1'-hydroxy-2',6',6'-trimethyl-4'-oxocyclohex-2'-enyl)-4-methylpyran-2-one, which on reduction by lithium aluminium hydride and reoxidation afforded (+/-)-abscisic acid stereospecifically.
- Cornforth, John,Hawes, John E.,Mallaby, Richard
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p. 179 - 185
(2007/10/02)
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- Facile synthesis of anhydromevalonolactone from ethyl acetoacetate
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Ethyl acetoacetate was transformed to 3-methylglutaconic anhydride, which upon LAH reduction and Jones oxidation afforded anhydromevalonolactone.
- Nangia,Rao,Prasuna
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p. 593 - 602
(2007/10/02)
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- A NEW PYRONE STRATEGY FOR THE SYNTHESIS OF 3-ACYLTETRAMIC ACIDS
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The potential of pyrones as precursors to 3-acyltetramic acids has been demonstrated by the conversion of 5-ethoxycarbonyl-4-methoxy-6-methyl-2-pyrone into a 3-acetyltetramic acid.
- Jones, Raymond C.F.,Patience, Jacqueline M.
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p. 3217 - 3218
(2007/10/02)
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- Reaction of Ethyl Acetoacetate with p-Toluenesulfonic Acid: Formation of Ethyl Isodehydroacetate and/or Ethyl p-Toluenesolfonate
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Treatment of ethyl acetoacetate with anhydrous p-toluenesulfonic acid at room temperature led to ethyl isodehydroacetate (1) in high yield by acid-catalysed condensation.On the other hand, in refluxing toluene, the unexpected ethyl ester of p-toluenesulfonic acid (2) was formed in moderate yield.This constitutes a new direct esterification of arenesulfonic acids. Keywords---ethyl acetoacetate; p-toluenesulfonic acid; ethyl isodehydroacetate; ethyl p-toluenesulfonate; condensation; direct esterification
- Nitta, Yoshihiro,Arakawa, Yasushi
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p. 1385 - 1388
(2007/10/02)
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