New Approach for the Synthesis of Isoxazoline-<i>N</i>-oxides

Kunetsky, Roman A.; Dilman, Alexander D.; Ioffe, Sema L.; Стручкова, Марина И.; Strelenko, Yury A.; Tartakovsky, Vladimir A.

doi:10.1021/ol0360602

Cited by 48 publications

(19 citation statements)

References 24 publications

(12 reference statements)

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“…Recently, Ioffe and co-workers [18] described interesting strategy for the preparation of five-membered, internal nitronic esters which is based on the elimination of the trimethylsilyl bromide (2) from 2-(trimethylsilyloxy)-3-bromo-3-methyl-isoxazolidine systems (1a-d).…”

Section: Introductionmentioning

confidence: 99%

Unexpected molecular mechanism of trimethylsilyl bromide elimination from 2-(trimethylsilyloxy)-3-bromo-3-methyl-isoxazolidines

Kącka‐Zych

Jasiński

2019

Theor Chem Acc

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The molecular mechanism of elimination of the trimethylsilyl bromide (2) from 2-(trimethylsilyloxy)-3-bromo-3-methylisoxazolidines (1a-d) has been analyzed within the molecular electron density theory using density functional theory calculations at the M06-2X(PCM)/6-31+G(d) computational level. These elimination reactions take place via a two-step mechanism involving an intermediate. Bonding evolution theory analysis allows to set apart seven phases along the reaction path. Elimination of trimethylsilyl bromide starts with rupture of the C1-Br2 bond of 2-(trimethylsilyloxy)-3-bromo-3-methyl-isoxazolidine (1a). Thereafter, we observed the formation of the N5-C1 double bond and the last step of this elimination is associated with formation of a new Br2-Si3 bond and breaking of the Si3-O4 bond.

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Section: Introductionmentioning

confidence: 99%

Unexpected molecular mechanism of trimethylsilyl bromide elimination from 2-(trimethylsilyloxy)-3-bromo-3-methyl-isoxazolidines

Kącka‐Zych

Jasiński

2019

Theor Chem Acc

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“…The structure assignment for nitronates 22a , 22b rests on a combination of typical spectral data. Thus, compounds 22a , 22b each have a strong IR absorption at 1652 cm −1 assigned as the nitronate C,N double bond stretching frequency based on published values for related five‐member cyclic nitronates . Additional IR bands characteristic of a nitro compound are present for compounds 22a , 22b .…”

Section: Resultsmentioning

confidence: 93%

“…In particular, the observed 13 C NMR chemical shifts for CH signals attributed to C‐5 (δ 100.7 and δ 99.7, respectively) are consistent with structures 22a , 22b but are inconsistent with the isomeric structures 24a , 24b in which the CH signals would be attributed to C‐4. Chemical shift values for compounds 25 and 26a , 26b are illustrative (Scheme ). For 24a , 24b , the CH chemical shifts should be δ 77–85 by comparison to C‐4 signals of 26a , 26b .…”

Section: Resultsmentioning

confidence: 99%

A new method for functionalizing α,γ‐dinitro compounds at the β‐position: application to the cyclization of β‐alkoxy‐α,γ‐dinitro compounds

Wade

Castillo

Paparoidamis

2013

J of Physical Organic Chem

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Treatment of 2,4-dinitropentane with bromine and sodium methoxide in methanol, affords formation of an ether product, 2,4-dibromo-3-methoxy-2,4-dinitropentane, in 59% yield as a mixture of three diastereomers. This observation has led to a general synthesis of 3-alkoxy-2,4-dibromo-2,4-dinitropentanes, obtained in 75-86% yield from 2,4-dibromo-2,4dinitropentane as the preferred reactant. 4-Bromo-2,4-dinitro-2-pentene has been identified as an intermediate in these reactions. The nitroalkene has been isolated and undergoes conjugate addition with alkoxides to afford the same ether products after brominative work-up. The nitroalkene undergoes conjugate addition with sodium azide to give 3-azido-2,4-dibromo-2,4-dinitropentane in 38% yield as a mixture of two isomers in which the (R*,R*) isomer predominates. Sequential treatment of 2,4-dibromo-2,4-dinitropentane with sodium methoxide followed by sodium iodide and acetic acid gives 3-methoxy-2,4-dinitropentane in 63% yield, the overall product of simple methoxylation of 2,4-dinitropentane. However, attempted complete debromination of 2,4-dibromo-3-methoxy-2,4-dinitropentane with excess sodium iodide and acetic acid results only in monodebromination to give 2-bromo-3-methoxy-2,4-dinitropentane in 86% yield. Likewise, 2-bromo-3-ethoxy-2,4-dinitropentane is formed in 93% yield from the ethoxy analog. A mechanistic rationale is offered for condition-specific removal of the second Br atom in these reactions. Treatment of 3-methoxy-2,4-dinitropentane with potassium acetate/iodine in dimethyl sulfoxide affords formation of 4,5-dihydro-3,4-dimethyl-3-methoxy-4-nitroisoxazole 2-oxide in 30% yield as a single diastereomer. Conversion of 2-bromo-3methoxy-2,4-dinitropentane in 15% yield to 4,5-dihydro-3,4-dimethyl-3-methoxy-4-nitroisoxazole 2-oxide is also possible by using potassium acetate in dimethyl sulfoxide. The mechanistic pathways for formation of 4,5-dihydro-3,4-dimethyl-3methoxy-4-nitroisoxazole 2-oxide apparently involve unstable 3-methoxy-1,2-dimethyl-1,2-dinitrocyclopropane as the common intermediate. Similarly, 2-bromo-3-ethoxy-2,4-dinitropentane affords 4,5-dihydro-3-ethoxy-3,4-dimethyl-4nitroisoxazole 2-oxide in 13% yield. a 0.1 M NaOMe. b 0.1-0.24 M NaX. c 1.7 M NaOMe. d 0.8 M NaOCH 2 Ph. e 0.15 M NaN 3 and 0.03 M NaOEt β-ALKOXY-α,γ-DINITRO COMPOUNDS

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“…All inorganic reagents, nitroethane, and 1‐nitropropane were commercial‐grade and used as received. The initial cyclic nitronates 2a ,3h 2b ,3f 2c ,3f 2e ,3f 2f ,3g 2g ,3h 2h ,3g 2m ,11a 2n ,19 2o ,20 2p ,20 2ac ,3h and 2ac′ ,3h and bis(oxy)enamines 3a ,3h 3b ,11c 3c ,11a 3d ,3h 3e ,11b 3f ,3g 3g ,3h 3h ,3g 3n ,20 3u ,10b 3v ,10a 3z ,10c 3aa ,10a 3ab ,10a 3ac ,3h and 3ac′ 3h were synthesized according to known methods. Nitronates 2d , and 2j – l were prepared following the procedure used for the synthesis of 2d 3h with small modifications: for compounds 2d , 2j , and 2l , the reaction mixtures were kept at –30 °C for 20 h, for compound 2k , the reaction mixture was kept at –30 °C for 30 min.…”

Section: Methodsmentioning

confidence: 99%

A General Metal‐Assisted Synthesis of α‐Halo Oxime Ethers from Nitronates and Nitro Compounds

Sukhorukov

Kapatsyna

Yi³

et al. 2014

Eur J Org Chem

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An approach to the synthesis of α‐halo oxime ethers from readily accessible nitronates and nitro compounds via bis(oxy)enamines is reported. A key step of the strategy involves the unprecedented reaction of bis(oxy)enamines with a metal (Co, Zn, Mg, Mn) halide that acts as both a promoter and halide (Br, I, Cl) source. A variety of cyclic and acyclic ethers of α‐halo oximes, including previously unavailable trimethylsilyl ethers of α‐iodo oximes, have been synthesized in good‐to‐high yields.

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New Approach for the Synthesis of Isoxazoline-N-oxides

Abstract: A strategy for the synthesis of isoxazoline-N-oxides (cyclic five-membered nitronates) from primary nitro compounds and olefins is described. The key step of the process involves 1,3-dipolar cycloaddition of corresponding 1-bromosilyl nitronates with alkenes. [reaction: see text]

Cited by 48 publications

References 24 publications

Unexpected molecular mechanism of trimethylsilyl bromide elimination from 2-(trimethylsilyloxy)-3-bromo-3-methyl-isoxazolidines

Unexpected molecular mechanism of trimethylsilyl bromide elimination from 2-(trimethylsilyloxy)-3-bromo-3-methyl-isoxazolidines

A new method for functionalizing α,γ‐dinitro compounds at the β‐position: application to the cyclization of β‐alkoxy‐α,γ‐dinitro compounds

A General Metal‐Assisted Synthesis of α‐Halo Oxime Ethers from Nitronates and Nitro Compounds

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