Unusual transformations of 2-isoxazolines

Королева, Е. В.; Lakhvich, F. A.

doi:10.1070/rc1997v066n01abeh000234

Cited by 13 publications

(6 citation statements)

References 56 publications

(69 reference statements)

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“…from the corresponding 3,6-disubstituted cyclohex-2-enones (I.5) and 2,5-disubstituted cyclohexanones (II.2) in the aromatisation of cyclohexenone or modifications of cyclohexanone fragments (Scheme 10) [37]. Investigations of the electro-optic and dynamic parameters of LC mixtures containing compounds (37)(38)(39)(40)(41)(42)(43)(44), presented in Table 5, have shown that they are really promising components of the materials for VA displays.…”

Section: Synthesis Of Liquid-crystalline and Anisotropic Compoundsmentioning

confidence: 98%

“…These compounds (37)(38)(39)(40)(41)(42)(43)(44) and polyfluoroderivatives similar to them are characterised a high value of negative dielectric anisotropy (-Δϵ) and allow the threshold voltage of the liquid-crystalline mixtures to decrease. Using the polyfluoroderivatives, we have developed the LC compositions with low the threshold voltage, fast switch-on and switch-off times and a wide temperature range of the nematic phase (from -30°C to +105°C) for VA displays [9,13,14].…”

Section: F CLmentioning

confidence: 99%

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Polyfunctional intermediates for the preparation of liquid-crystalline and anisotropic materials

et al. 2015

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This paper describes the polyfunctional intermediates for the preparation of various anisotropic and liquidcrystalline compounds with different combinations of cyclic, bridge, terminal fragments and lateral substituents. Both chiral and nonchiral nematic, smectic mesomorphic and anisotropic compounds can be prepared by the transformations of the corresponding 3,6-disubstituted cyclohex-2-enones, trans-2,5-disubstituted cyclohexanones, 3,5-disubstitiuted 2-isoxazolines, substituted cyclohex-2-enonyl 2-isoxazolines, 1,2-disubstitiuted cyclopropanols and substituted unsaturated epoxyketones.

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Section: Synthesis Of Liquid-crystalline and Anisotropic Compoundsmentioning

confidence: 98%

Section: F CLmentioning

confidence: 99%

Polyfunctional intermediates for the preparation of liquid-crystalline and anisotropic materials

et al. 2015

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“…Bond lengths ( A) Cl(1)eC (11) 1.7777 (18) O(2)eC(10) 1.451(2) Cl(2)eC (11) 1.7862(18) C(8)eC (9) 1.503(2) N(1)eC (8) 1.280(2) C(9)eC(10) 1.524(3) N(1)eO (2) 1.431(2) C(10)eC(11) 1.523 (3) Bond angles ( ) C(8)eN(1)eO (2) 108.86(15) O(2)eC(10)eC (11) 107.28(15) N(1)eO(2)eC (10) 108.87(13) O(2)eC(10)eC (9) 104.74(14) N(1)eC(8)eC (4) 121.86(17) C(11)eC(10)eC (9) 111.55(15) N(1)eC(8)eC (9)) 114.12(16) C(10)eC(11)eCl(1) 110.55(13) C(4)eC(8)eC (9) 124.00(16) C(10)eC(11)eCl (2) 108.90(13) C(8)eC(9)eC (10) 100.71 (15) Cl (1) …”

Section: Preparation Of 22-dichlorovinylacetophenone Oximesmentioning

confidence: 98%

A new and efficient approach to isoxazolines. First synthesis of 3-aryl-5-dichloromethyl-2-isoxazolines

Guirado¹,

Martiz²,

Andreu³

et al. 2011

Tetrahedron

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a b s t r a c tAn efficient synthetic method for 3-aryl-5-dichloromethyl-2-isoxazolines has been established. Reactions between anhydrous chloral and acetophenones in hot acetic acid lead to 1-aryl-4,4,4-trichloro-3-hydroxybutan-1-ones (chloralacetophenones), which provided 1-aryl-4,4-dichlorobut-3-en-1-ones (2,2-dichlorovinylacetophenones) by dehydration and subsequent electrochemical reduction. These b,g-unsaturated enones reacted with hydroxylamine yielding oxime intermediates whose treatment with aqueous sodium hydroxide gave novel 3-aryl-5-dichloromethyl-2-isoxazolines in fair to high yields. The molecular structure of a member of this family of compounds, 5-dichoromethy1-3-(4-methoxyphenyl)-2-isoxazoline, was determined by X-ray crystallography.

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“…It is generally considered that 1,3-cyclodecomposition under the influence of bases goes via the generation of an anion at the C (5) atom of the ring [6,7,10]. However, the most acidic hydrogens are at C (3) in 3-substituted 2-isoxazolines and at C (4) in 3-unsubstituted isoxazolines [11,12].…”

mentioning

confidence: 99%

“…The cryptobasic reducing agent K-selectride has a nucleophilic character. Molybdenum hexacarbonyl reacts with 2-isoxazolines with the intermediate formation of a vinyl-nitrene complex with delocalization of the π-d electrons from the metal into the C=N-O π-orbital of the heterocycle, which makes easy rupture of the N-O bond possible [10,13]. …”

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confidence: 99%

2-Isoxazolines with an electron-acceptor substituent at C(5) in reactions with nucleophilic reagents

Королева

Bondar

Katok

et al. 2007

Chem Heterocycl Compd

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Depending on the substituent at position 5 of the heterocycle, reaction of 2-isoxazolines with K-selectride, molybdenum hexacarbonyl, dimsyl sodium, and butyl lithium gave 1,3-cyclodecomposition, aromatization of the isoxazoline ring, or reduction of the functional groups in the substituted isoxazolines.We described previously the reaction of 3-R-5-(4-pyridyl)-2-isoxazols with K-selectride (KBH(s-Bu) 3 ) and other organometallic reagents (butyl lithium, dimsyl sodium, and molybdenum hexacarbonyl) which occurred by decomposition of the isoxazoline ring at the N-O and C (3) -C (4) bonds to give nitriles and 4-vinylpyridine [1-4]. However, 2-isoxazolines with phenyl, 2-pyridyl, or 2-oxo-1-pyrrolidyl substituents at C (5) did not give products of cyclodecomposition in such reactions [2, 5]. Similar 1,3-cyclodecomposition under the influence of bases was known for a series of 5-acylisoxazolines and 5-nitroisoxazolines [6, 7]. Only products of 1,4-cyclodecomposition were isolated from reactions of 2-isoxazolines with metal polycarbonyls [8,9].The decomposition of the heterocycle of 2-isoxazolines at two bonds is formally the reverse of the synthesis of the heterocycle and not infrequently complicates the typical decomposition of the ring of 2-isoxazolines, which normally occurs at one of the bonds of the N-O-C unit. It is generally considered that 1,3-cyclodecomposition under the influence of bases goes via the generation of an anion at the C (5) atom of the ring [6,7,10]. However, the most acidic hydrogens are at C (3) in 3-substituted 2-isoxazolines and at C (4) in 3-unsubstituted isoxazolines [11,12]. 5-endo-Deprotonation is generally uncharacteristic but may occur when there are an electron-acceptor substituents at C (5) , capable of creating a considerable increase in the acidity of the H-5 proton and facilitating the stabilization of the anion formed.To determine the limit of the applicability of the 1,3-cyclodecomposition reaction it was expedient to compare the reactions of 2-isoxazolines, having electron-acceptor substituents at C (5) , with typical bases, on the one hand, and with nucleophilic organometallic reagents, on the other hand. The cryptobasic reducing agent K-selectride has a nucleophilic character. Molybdenum hexacarbonyl reacts with 2-isoxazolines with the intermediate formation of a vinyl-nitrene complex with delocalization of the π-d electrons from the metal into the C=N-O π-orbital of the heterocycle, which makes easy rupture of the N-O bond possible [10,13].

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Unusual transformations of 2-isoxazolines

Cited by 13 publications

References 56 publications

Polyfunctional intermediates for the preparation of liquid-crystalline and anisotropic materials

Polyfunctional intermediates for the preparation of liquid-crystalline and anisotropic materials

A new and efficient approach to isoxazolines. First synthesis of 3-aryl-5-dichloromethyl-2-isoxazolines

2-Isoxazolines with an electron-acceptor substituent at C(5) in reactions with nucleophilic reagents

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