145616-48-4Relevant academic research and scientific papers
Synthesis of 3,6-Dihydro-2 H-1,2-oxazines via Dimethylsulfoxonium Methylide Addition to α,β-Unsaturated Nitrones
Hasegawa, Megumi,Suga, Takuya,Soeta, Takahiro,Ukaji, Yutaka
, p. 11258 - 11264 (2020/10/12)
A unique and efficient formation of 3,6-dihydro-2H-1,2-oxazines starting from α,β-unsaturated nitrones has been achieved. The nucleophilic addition of dimethylsulfoxonium methylide to the C-N bond of an α,β-unsaturated nitrone to form an aziridine N-oxide followed by the Meisenheimer rearrangement affords 3,6-dihydro-2H-1,2-oxazine in up to 70% yield. Methylene was confirmed to be incorporated at the C3 position of the ring. A wide range of β-aryl-substituted α,β-unsaturated nitrones were applicable to this reaction.
Boronic acid catalysis for mild and selective [3+2] dipolar cycloadditions to unsaturated carboxylic acids
Zheng, Hongchao,McDonald, Robert,Hall, Dennis G.
supporting information; experimental part, p. 5454 - 5460 (2010/09/15)
Herein, the concept of boronic acid catalysis (BAC) for the activation of unsaturated carboxylic acids is applied in several classic dipolar [3 + 2] cycloadditions involving azides, nitrile oxides, and nitrones as partners. These cycloadditions can be used to produce pharmaceutically interesting, small heterocyclic products, such as triazoles, isoxazoles, and isoxazolidines. These cycloadducts are formed directly and include a free carboxylic acid functionality that can be employed for fur-ther transformations, thereby avoiding prior masking or functionalization. In all cases, BAC provides faster reactions, under milder conditions, with much improved product yields and regioselectivities. In some instances, such as triazole formation from the reaction of azides with 2-alkynoic acids, catalysis with ort/io- nitrophenylboronic acid circumvents the undesirable product decarboxylation observed when using thermal activation. By using NMR spectroscopic studies, the boronic acid catalyst was shown to provide activation by a LUMO-lowering effect in the unsaturated carboxylic acid, likely via a monoacylated hemiboronic ester intermediate.
A torquoselective extrusion of isoxazoline N-oxides. Application to the synthesis of aryl vinyl and divinyl ketones for Nazarov cyclization
Canterbury, Daniel P.,Herrick, Ildiko R.,Um, Joann,Houk,Frontier, Alison J.
experimental part, p. 3165 - 3179 (2009/09/05)
A mild, convenient reaction sequence for the synthesis of Nazarov cyclization substrates is described. The [3+2] dipolar cycloaddition of a nitrone and an electron-deficient alkyne gives an isolable isoxazoline intermediate, which upon oxidation undergoes stereoselective extrusion of nitrosomethane to give aryl vinyl or divinyl ketones.
Sequential 1,3-dipolar cycloaddition of nitrones to β-(2-aminophenyl) α,β-ynones and cyclocondensation: A new entry to the isoxazolino[4,5-c]quinoline ring
Abbiati, Giorgio,Arcadi, Antonio,Marinelli, Fabio,Rossi, Elisabetta,Verdecchia, Mirella
experimental part, p. 1027 - 1031 (2009/07/17)
The reaction of β-(2-aminophenyl) α,β-ynones with N-methyl nitrones provides a simple and efficient entry to the isoxazol-Germany, 2009) ino[4,5-c]quinoline ring system through a sequential 1,3-dipolar cycloaddition/annulation process.
Ring-opening of isoxazolidine system: Homologation of 3-aryl into 3-styryl nitrones via intermediate 5-hydroxy-isoxazolidines
Chiacchio, Ugo,Liguori, Angelo,Romeo, Giovanni,Sindona, Giovanni,Uccella, Nicola
, p. 9473 - 9482 (2007/10/02)
High yield conversion of 3-aryl-5-ethoxy-isoxazolidines into 3-styryl nitrones has been achieved by 1,5 h refluxing in aq. H2SO4 or catalytic p-toluensulfonic acid/ethanol media. The rearrangement pathway is interpretable on the basis of the ring-opening process of intermediate 5-hydroxy-isoxazolidines. Formation of a masked 5-OH function has been also developed by basic or acid treatment of 5-acetoxy-isoxazolidines.
