ChemInform Abstract: Regio‐ and Faceselective Formation of 1:1 and 2:1 Adducts by 1,3‐Dipolar Cycloaddition of Benzonitrile Oxide to 2‐Alkoxy‐5,6‐dihydro‐2H‐pyrans.

Blake, Alexander J.; Dawson, I. M. P.; Forsyth, A. C.; Johnson, Trevor; Paton, R. M.; Rennie, R. A. C.; Taylor, P.

doi:10.1002/chin.198911074

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“…The structural characterisation of the new liquid crystalline cycloadducts 7a-d was made by means of combustion analysis, proton ( 1 H), carbon ( 13 C) NMR spectroscopic techniques (H -H Correlation Spectroscopy H,H-COSY, Heteronuclear Multiple Quantum Correlation HMQC and Heteronuclear Multiple Bond correlation HMBC), EI-MS and highresolution mass spectrometry (HRMS) (ESI) [15,20,23,[40][41][42][43].…”

Section: Theoretical Calculationsmentioning

confidence: 99%

The 2:1 cycloadducts from [3 + 2] 1,3-dipolar cycloaddition of nitrile oxide and vinylacetic acid. Synthesis and liquid crystal behaviour

et al. 2012

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2012The 2:1 cycloadducts from [3+2] 1,3-dipolar cycloaddition of nitrile oxide and vinylacetic acid. Synthesis and liquid crystal behaviour LIQUID CRYSTALS, ABINGDON, v. 39, n. 2,pp. 175-184, FEB, 2012 http://www.producao.usp.br/handle/BDPI/42740 This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden.The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. Four liquid crystals (LC) 3,7a-bis(4-alkyloxyphenyl)-7,7a-dihydro-6H-isoxazolo[2,3-d][1,2,4]oxadiazol-6-yl)acetic acid (7a-d) were synthesised and the mesomorphic behaviour reported. The LCs were characterised as 2:1 bisadducts, which were obtained from a double [3 + 2] 1,3-dipolar cycloaddition. In the first step, the cycloaddition of 4-alkyloxyphenylnitrile oxide (4a-d) and vinylacetic acid (5) gave the initial unobserved 1:1 cycloadducts 2-[3-(4-alkyloxyphenyl)-4,5-dihydroisoxazol-5-yl]acetic acid (6a-d). In the second step, the addition of a second equivalent of 4 to 6 yielded the 2:1 bisadducts 7a-d without any traces of 6. All compounds 7a-d were unstable during the transition from the mesophase to the isotropic state upon first heating as evidenced by the large peaks in the differential scanning calorimetry traces. Due to the chemical instability of the compounds upon heating, the transition temperature related to the smectic C to smectic A transitions was acquired by means of an image processing method. X-Ray diffraction experiments were also used to analyse the liquid-crystalline phases. A theoretical calculation was performed using density functional theory (DFT) methods at the PBE1PBE/6-311+G(2d,p) level (with solvent effect) in order to get information about the energetic profile of the 2:1 cycloaddition. DFT studies revealed that the cycloaddition process is controlled by the HOMO (dipolarophile) -LUMO (1,3-dipole) , and that the double [3 + 2] 1,3-dipolar cycloaddition reaction is quite possible.

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Section: Theoretical Calculationsmentioning

confidence: 99%

The 2:1 cycloadducts from [3 + 2] 1,3-dipolar cycloaddition of nitrile oxide and vinylacetic acid. Synthesis and liquid crystal behaviour

et al. 2012

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ChemInform Abstract: Regio‐ and Faceselective Formation of 1:1 and 2:1 Adducts by 1,3‐Dipolar Cycloaddition of Benzonitrile Oxide to 2‐Alkoxy‐5,6‐dihydro‐2H‐pyrans.

Abstract: Reaction of deficient benzonitrile oxide (II) (obtained in situ by dehydrochlorination of benzohydroximoyl chloride) with (I) (models for 2,3‐unsaturated sugars) leads to monoadducts (III), (IV), (Va), and by‐products (VI) and (VII).

Cited by 1 publication

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The 2:1 cycloadducts from [3 + 2] 1,3-dipolar cycloaddition of nitrile oxide and vinylacetic acid. Synthesis and liquid crystal behaviour

The 2:1 cycloadducts from [3 + 2] 1,3-dipolar cycloaddition of nitrile oxide and vinylacetic acid. Synthesis and liquid crystal behaviour

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