- Sc(OTf)3-catalyzed [3 + 2]-cycloaddition of nitrones with ynones
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An efficient approach to access functionalized (2,3-dihydroisoxazol-4-yl) ketones has been developed by reacting nitrones 4 with ynones 7 or terminal ynones 10 in a one-pot fashion. The reaction went through a formal Sc(OTf)3-catalyzed [3 + 2]-cycloaddition process to generate a number of functionalized (2,3-dihydroisoxazol-4-yl) ketones 11aa-11aw, 11ba-11la and 12aa-12ae in moderate to good yields. This journal is
- He, Chun-Ting,Han, Xiao-Li,Zhang, Yan-Xue,Du, Zhen-Ting,Si, Chang-Mei,Wei, Bang-Guo
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p. 457 - 466
(2021/01/29)
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- α,β-Unsaturated Amides as Dipolarophiles: Catalytic Asymmetric exo-Selective 1,3-Dipolar Cycloaddition with Nitrones
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1,3-Dipolar cycloaddition is a commonly exploited method to access 5-membered chemical entities with a variety of peripheral functionalities and their stereochemical arrangements. Nitrones are isolable 1,3-dipoles that exhibit sufficient reactivity toward electron-deficient olefins in the presence of Lewis acids to deliver highly substituted isoxazolidines. Herein we document that α,β-unsaturated amides, generally regarded as barely reactive in a 1,3-dipolar reaction manifold, were effectively activated using the designed 7-azaindoline auxiliary in an In(OTf)3/bishydroxamic acid catalytic system. The broad substrate scope and clean removal of the 7-azaindoline auxiliary from the product highlight the synthetic utility of the present catalysis.
- Zhang, Ming,Kumagai, Naoya,Shibasaki, Masakatsu
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supporting information
p. 12450 - 12455
(2017/09/18)
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- Dual Role of Pyrrolidine and Cooperative Pyrrolidine/Pyrrolidinium Effect in Nitrone Formation
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The formation of nitrones by direct condensation between equimolecular amounts of N-substituted hydroxylamine hydrochlorides and aromatic or aliphatic aldehydes is efficiently promoted by pyrrolidine in a matter of minutes under very mild conditions in almost quantitative yields after a simple filtration through a short pad of silica gel. According to theoretical, spectroscopic, and experimental studies, this success is due to the ability of pyrrolidine to liberate the hydrochloride of the hydroxylamine and catalyze the reaction via iminium activation ion. Moreover, a cooperative pyrrolidine/pyrrolidinium chloride effect facilitates several steps of the catalytic cycle through proton transfer without hampering the nucleophilicity of the hydroxylamine by protonation.
- Morales, Sara,Guijarro, Fernando G.,Alonso, Inés,García Ruano, José Luis,Cid, M. Belén
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- Modified N,O-nucleosides: Design, synthesis, and anti-tumour activity
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A preliminary library of modified N,O-nucleosides was prepared and tested on a selected number of human cancer lines that include SKOV3, SW480, and K562. Thymine, N-benzyl substituents, and aromatic rings contribute to an increase of the biological activity, up to 10-25μM, that appeared also reliant on the calculated lipophilicity of the nucleosides, expressed as cLogP, where P represents the partition coefficient of a solute between n-octanol and water. CSIRO 2014.
- Maiuolo, Loredana,Bortolini, Olga,De Nino, Antonio,Russo, Beatrice,Gavioli, Riccardo,Sforza, Fabio
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p. 670 - 674
(2014/05/06)
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- A magnetoclick imidazolidinone nanocatalyst for asymmetric 1,3-dipolar cycloadditions
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A 1,3-dipolar azide-alkyne cycloaddition has been used to prepare a magnetic nanoparticle immobilized MacMillan catalyst that catalyzes the enantioselective 1,3-dipolar cycloaddition between nitrones and α,β-unsaturated aldehydes. The catalyst can be recovered and recycled for five consecutive runs without any significant loss in yields and diastereo- and enantioselectivities of the isoxazolidines. Copyright
- Pagoti, Sreenivasarao,Dutta, Debasish,Dash, Jyotirmayee
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p. 3532 - 3538
(2014/01/06)
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- Enantioselective nitrone cycloadditions of α,β-unsaturated 2-acyl imidazoles catalyzed by bis(oxazolinyl)pyridine-cerium(IV) triflate complexes
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Enantioselective nitrone cycloadditions with β-substituted α,β-unsaturated 2-acyl imidazoles catalyzed by bis(oxazolinyl) pyridine-cerium(IV) triflate complexes 1 have been reported. The isoxazolidine products were efficiently transformed into densely functionalized β′-hydroxy-β-amino acid derivatives.
- Evans, David A.,Song, Hyun-Ji,Fandrick, Keith R.
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p. 3351 - 3354
(2007/10/03)
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- Asymmetric 1,3-dipolar cycloaddition reaction of nitrones and acrolein with a bis-titanium catalyst as chiral Lewis acid
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A μ-oxo-type chiral bis-Ti(IV) oxide (S,S)-1 can be successfully utilized in the asymmetric 1,3-dipolar cycloaddition reactions between various nitrones 2 and acrolein to give the corresponding isoxazolidines with high to excellent enantioselectivities. F
- Kano, Taichi,Hashimoto, Takuya,Maruoka, Keiji
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p. 11926 - 11927
(2007/10/03)
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