Features of the (2+3)-cycloaddition of trifluoroacetonitrile oxide

Truskanova, T. D.; Vasil'ev, N. V.; Gontar, A. F.; Kolomiets, A. F.; Sokol'skii, G. A.

doi:10.1007/bf00472756

Cited by 5 publications

(4 citation statements)

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“…Trifluoroacetonitrile N-oxide, CF 3 CNO (1), is often used in [2 + 3] cycloaddition reactions where five-membered heterocycles, for example, oxazoles, oxazolines, isoxazoles, and isoxazolines, including Diels-Alder adducts, can be prepared. [6][7][8][9][10][11][12] Recently, 1 has proven to be of interest in medical applications, acting as a reagent for preparing tachykinin receptor antagonists 13 as well as in the production of herbicides, pesticides, and insecticides. 14 In most cases, 1 is generated as a reactive dipolarophile in solution from Br-or Cl-oximes, specifically trifluoroacetohydroximoyl bromide and chloride, respectively, since it has been stated 6 to be unstable in solution "even at a temperature below -20°".…”

Section: Introductionmentioning

confidence: 99%

“…Nonetheless, they are widely used in organic chemistry for the syntheses of heterocycles and natural products, − mainly by in situ preparation and subsequent 1,3-dipolar reaction with various substrates. Trifluoroacetonitrile N -oxide, CF 3 CNO ( 1 ), is often used in [2 + 3] cycloaddition reactions where five-membered heterocycles, for example, oxazoles, oxazolines, isoxazoles, and isoxazolines, including Diels−Alder adducts, can be prepared. − Recently, 1 has proven to be of interest in medical applications, acting as a reagent for preparing tachykinin receptor antagonists as well as in the production of herbicides, pesticides, and insecticides…”

Section: Introductionmentioning

confidence: 99%

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Gas-Phase Infrared and ab Initio Study of the Unstable CF₃CNO Molecule and Its Stable Furoxan Ring Dimer

2005

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The unstable trifluoroacetonitrile N-oxide molecule, CF3CNO, has been generated in high yield in the gas phase from CF3BrC=NOH and studied for the first time by gas-phase mid-infrared spectroscopy. Cold trapping of this molecule followed by slow warming forms the stable ring dimer, bis(trifluoromethyl)furoxan, also investigated by gas-phase infrared spectroscopy. The spectroscopy provides an investigation into the vibrational character of the two molecules, the assignments supported by calculations of the harmonic vibrational frequencies using in the case of CF3CNO both ab initio (CCSD(T)) and density functional theory (B3LYP) and B3LYP for the ring dimer. The ground-state structures of both molecules were investigated at the B3LYP level of theory, with CF3CNO further investigated using coupled-cluster. The CCSD(T) method suggests a slightly bent (C(s)) structure for CF3CNO, while the B3LYP method (with basis sets ranging from 6-311G(d) to cc-pVTZ) suggests a close-to-linear or linear CCNO chain. The CCN bending potential in CF3CNO was explored at the CCSD(T)(fc)/cc-pVTZ level, with the results suggesting that CF3CNO exhibits strong quasi-symmetric top behavior with a barrier to linearity of 174 cm(-1). Since both isomerization and dimerization are feasible loss processes for this unstable molecule, the relative stability of CF3CNO with respect to the known cyanate (CF3OCN), isocyanate (CF3NCO), and fulminate (CF3ONC) isomers and the mechanism of the dimerization process to the ring furoxan and other isomers were studied with density functional theory.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Gas-Phase Infrared and ab Initio Study of the Unstable CF₃CNO Molecule and Its Stable Furoxan Ring Dimer

2005

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“…The compound was purified by distillation in vacuo : 9.09 g (75%); colorless liquid; bp 42–45 °C/11 mbar; spectral and physical data were analogous to that reported …”

Section: Methodsmentioning

confidence: 61%

“…The compound was purified by distillation in vacuo: 9.09 g (75%); colorless liquid; bp 42−45 °C/11 mbar; spectral and physical data were analogous to that reported. 50 Ethyl 3-(Difluoromethyl)-4,5-dihydroisoxazole-5-carboxylate (2i). The compound was purified by distillation in vacuo: 7.20 g (65%), colorless liquid; bp 67−70 °C/15 mbar; 1 H NMR (400 MHz, CDCl 3 ) δ 6.48 (t, J = 53.7 Hz, 1H), 5.31−4.96 (m, 1H), 4.25 (q, J = 7.1 Hz, 2H), 3.46−3.34 (m, 2H), 1.30 (t, J = 7.1 Hz, 3H); 13 C{ 1 H} NMR (101 MHz, CDCl 3 ) δ 168.9, 152.5 (t, J = 31.6 Hz), 109.3 (t, J = 235 Hz), 78.9, 62.4, 34.9, 14.1; 19 Representative Procedure for the Hydrogenation of Isoxazolines 2.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Reductive Recyclization of sp³-Enriched Functionalized Isoxazolines into α-Hydroxy Lactams

et al. 2021

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An efficient synthesis (up to a 200 g scale) of 3hydroxypyrrolidin-2-ones bearing alkyl substituents or functional groups at the C-5 position is described. The reaction sequence started from 1,3-dipolar cycloaddition of in situ generated nitrile oxides with (meth-)acrylates into 3-substituted isoxazoline-5carboxylates. The catalytic hydrogenolysis of the isoxazoline N−O bond was optimal upon using H 2 (1 atm) at rt, with the following order of the catalyst activity: Pd−C > Pd(OH) 2 −C > Pt−C. The reactions with Pt−C were more selective for the synthesis of pyrrolidones, while Pd−C provided the fastest conversion rates. The stirring efficiency had a positive impact on conversion rather than elevated temperatures (up to 40 °C) or pressure (up to 50 atm). The diastereoselectivity was governed mainly by steric factors, with a dr of 1:1 to 3:1 (cis-and trans-isomers could be separated). Higher homologues (isoxazolinylacetates and -propanoates) were suitable for the synthesis of 6-or 7-substituted 4-hydroxypiperidones and 5-hydroxyazepanones, respectively. The proposed methods are tolerant to functional groups, including CF 3 (but not CHF 2 or CH 2 Cl), ester, and most N-Boc-protected amines. The utility of hydroxyl groups in lactams was shown by functional group transformations. Hydrogenolysis of C(5)-functionalized isoxazolines, bearing trimethylsilyl, phosphonate, or sulfone groups, was also studied to demonstrate limitations.

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Difluoromethyl Nitrile Oxide (CF₂HCNO): A Neglected Chemical Reagent

et al. 2017

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A novel chemical reagent – difluoromethyl nitrile oxide, CF2HCNO – was generated in situ for the first time. The synthesis commenced with ethyl difluoroacetate and included only two chemical steps. The difluoromethyl nitrile oxide smoothly participated in [3+2]‐cycloaddition reactions with alkynes and enamines to give CF2H‐isoxazoles; these products are promising cores for agrochemistry. A representative CHF2‐isoxazole was incorporated into the known fungicide Fluxapyroxad (BASF), and the synthesized analogue showed higher antifungal activity than the parent fungicide.

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Features of the (2+3)-cycloaddition of trifluoroacetonitrile oxide

Cited by 5 publications

References 3 publications

Gas-Phase Infrared and ab Initio Study of the Unstable CF₃CNO Molecule and Its Stable Furoxan Ring Dimer

Gas-Phase Infrared and ab Initio Study of the Unstable CF₃CNO Molecule and Its Stable Furoxan Ring Dimer

Reductive Recyclization of sp³-Enriched Functionalized Isoxazolines into α-Hydroxy Lactams

Difluoromethyl Nitrile Oxide (CF₂HCNO): A Neglected Chemical Reagent

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Features of the (2+3)-cycloaddition of trifluoroacetonitrile oxide

Cited by 5 publications

References 3 publications

Gas-Phase Infrared and ab Initio Study of the Unstable CF3CNO Molecule and Its Stable Furoxan Ring Dimer

Gas-Phase Infrared and ab Initio Study of the Unstable CF3CNO Molecule and Its Stable Furoxan Ring Dimer

Reductive Recyclization of sp3-Enriched Functionalized Isoxazolines into α-Hydroxy Lactams

Difluoromethyl Nitrile Oxide (CF2HCNO): A Neglected Chemical Reagent

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Gas-Phase Infrared and ab Initio Study of the Unstable CF₃CNO Molecule and Its Stable Furoxan Ring Dimer

Gas-Phase Infrared and ab Initio Study of the Unstable CF₃CNO Molecule and Its Stable Furoxan Ring Dimer

Reductive Recyclization of sp³-Enriched Functionalized Isoxazolines into α-Hydroxy Lactams

Difluoromethyl Nitrile Oxide (CF₂HCNO): A Neglected Chemical Reagent