Condition‐Based Selective Synthesis of 3,4,5‐Trisubstituted Isoxazoline N<i>‐</i>oxides, 4,5‐Dihydroisoxazoles and Isoxazoles

Chen, Xinfei; Peng, Yanqing; Yu, Weiwei; Zhang, Xiao; Shao, Xusheng; Xu, Xiaoyong; Li, Zhong

doi:10.1002/slct.201800839

Cited by 2 publications

(3 citation statements)

References 55 publications

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“…There have been several studies of the formation of isoxazoline N -oxides from α-nitro-α,β-unsaturated esters with C–H acids such as secondary nitroalkane [ 15 ], (ethoxycarbonylmethyl)dimethylsulfonium salt [ 16 ], (ethoxycarbonylmethyl)ammonium salt [ 17 ], (ethoxycarbonylmethyl)pyridinium salt [ 18 ], α-halomalonate [ 19 ], and α-iodo aldehyde [ 20 ]. β,β-Dimethoxynitroethene is also usable as a nucleophile in this protocol [ 21 ]. Among these, only two methods employ a nitro group as a leaving group [ 15 , 21 ].…”

Section: Resultsmentioning

confidence: 99%

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Comparison of Substituting Ability of Nitronate versus Enolate for Direct Substitution of a Nitro Group

2020

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α-Nitrocinnamate underwent the conjugate addition of an active methylene compound such as nitroacetate, 1,3-dicarbonyl compound, or α-nitroketone, and the following ring closure afforded functionalized heterocyclic frameworks. The reaction of cinnamate with nitroacetate occurs via nucleophilic substitution of a nitro group by the O-attack of the nitronate, which results in isoxazoline N-oxide. This protocol was applicable to 1,3-dicarbonyl compounds to afford dihydrofuran derivatives, including those derived from direct substitution of a nitro group caused by O-attack of enolate. It was found the reactivity was lowered by an electron-withdrawing group on the carbonyl moiety. When α-nitroketone was employed as a substrate, three kinds of products were possibly formed; of these, only isoxazoline N-oxide was identified. This result indicates that the substituting ability of nitronate is higher than that of enolate for the direct SN2 substitution of a nitro group.

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Section: Resultsmentioning

confidence: 99%

“…β,β-Dimethoxynitroethene is also usable as a nucleophile in this protocol [ 21 ]. Among these, only two methods employ a nitro group as a leaving group [ 15 , 21 ]. In these reactions, the nucleophilicity of the nitronate ion is relatively high.…”

Section: Resultsmentioning

confidence: 99%

Comparison of Substituting Ability of Nitronate versus Enolate for Direct Substitution of a Nitro Group

2020

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“…However, no general strategy can be used to afford the functionalized nitro precursors. Thus, intermolecular connection synthesis strategies have been developed, and there are two main types: (1) formal [3 + 2] cascade approaches and (2) formal [4 + 1] annulation approaches . In addition, it is reported that β-hydroxy ketoximes can be candidates to generate isoxazoline N -oxides, which undergo an intramolecular N–O coupling process by some additive oxidants .…”

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Synthesis of 4-Oxoisoxazoline N-Oxides via Pd-Catalyzed Cyclization of Propargylic Alcohols with tert-Butyl Nitrite

et al. 2019

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A cyclization of propargylic alcohols with tertbutyl nitrite at room temperature in air was achieved using Pd(OAc) 2 as catalyst. The first reported 4-oxoisoxazoline Noxides could be directly accessed from a range of multisubstituted propargylic alcohols in moderate to excellent yields under mild conditions. Density functional theory calculations indicated that the reaction proceeds through a palladiumcatalyzed NO 2 addition that efficiently generates a ketoxime radical, which eventually produces 4-oxoisoxazoline N-oxide.N itrogenous organic molecules play a crucial role in enriching the carbon-based natural world and are prevalent in compounds investigated in the pharmaceutical industry, 1 the agriculture industry, 2 organic synthesis, 3 and biological research. 4 Moreover, aza-heterocyclic compounds, a class of representative nitrogenous compounds, have drawn extensive attention for their potential biological and pharmaceutical activities. 5 In particular, isoxazoline N-oxides exhibit unique reactivity for the particular structure in this family and are well-known to be versatile building blocks in chemical synthesis. 6 There are several methods for synthesizing isoxazoline Noxides on the basis of relevant literature. In general, isoxazoline N-oxides can be prepared from functionalized aliphatic nitro compounds via intramolecular O-alkylation. 7 However, no general strategy can be used to afford the functionalized nitro precursors. Thus, intermolecular connection synthesis strategies have been developed, and there are two main types: (1) formal [3 + 2] cascade approaches 8 and (2) formal [4 + 1] annulation approaches. 9 In addition, it is reported that βhydroxy ketoximes can be candidates to generate isoxazoline N-oxides, which undergo an intramolecular N−O coupling process by some additive oxidants. 10 In this regard, although

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Condition‐Based Selective Synthesis of 3,4,5‐Trisubstituted Isoxazoline N‐oxides, 4,5‐Dihydroisoxazoles and Isoxazoles

Cited by 2 publications

References 55 publications

Comparison of Substituting Ability of Nitronate versus Enolate for Direct Substitution of a Nitro Group

Comparison of Substituting Ability of Nitronate versus Enolate for Direct Substitution of a Nitro Group

Synthesis of 4-Oxoisoxazoline N-Oxides via Pd-Catalyzed Cyclization of Propargylic Alcohols with tert-Butyl Nitrite

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