Synthesis of liquid-crystalline 3,5-diarylisoxazolines

Tavares, Aline; Ritter, Olga Maria Schimidt; Vasconcelos, Ursula Bohlke; Arruda, Bárbara Campiol; Schrader, Abel; Schneider, Paulo H.; Merlo, Aloir A.

doi:10.1080/02678290903432098

Cited by 23 publications

(11 citation statements)

References 41 publications

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“…No espectro de RMN 13 C da isoxazolina 5b foram observados os sinais referentes ao anel isoxazolínico 3,5-substituído em 39,0 ppm relativo ao C 4 do anel, 77,7 ppm relativo ao C 5 e em 155,5 ppm relativo ao C 3 . 18 Análises dos espectros de RMN 1 H, 13 C e IV confirmaram a inserção do grupo polimerizável acrilato na estrutura final. Na Figura 2 Para efeito comparativo foram preparados os homopolímeros poliacrilato 12, contendo o grupo terminal nitrila, e poliacrilato de mentila 13, a partir da reação de polimerização radicalar dos respectivos monômeros 7a e 9.…”

Section: Resultsunclassified

Síntese e caracterização de copolímeros de cadeia lateral derivados de acrilatos de 4,5-di-hidroisoxazol e do (-)-mentol

Passo¹,

Merlo²,

Eccher³

et al. 2012

Quím. Nova

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Recebido em 28/10/11; aceito em 30/3/12; publicado na web em 10/7/12 SYNTHESIS AND CHARACTERIZATION OF COPOLYMERS 4,5-DIHYDROISOXAZOLE AND (-)-MENTHYL ACRYLATES. Five monomers 5-[4-(5-cyano-4,5-dihydroisoxazol-3-yl)phenoxy]undecyl acrylate (7a); n-alkyl 3-{4- [5-(acryloyloxyundecyl) oxyphenyl]}-4,5-dihydroisoxazole-5-carboxylate (7b,c for n-butyl and n-hexyl, respectively); 3-{4- [5-(acryloyloxyundecyl) oxyphenyl]}-4,5-dihydroisoxazole-5-carboxylic acid (7d) and (1R,2S,5R)-2-isopropyl-5-methylcyclohexyl acrylate (9) and the corresponding copolymers 10a-d, 11 and homopolymers 12 from 7a and 13 from 9 were designed and synthesized. Except for acrylate 9 which is derived from (-)-menthol, all of the monomers belong to the series containing the isoxazoline ring linked to the acrylate unit by a flexible spacer chain of eleven methylene units. They presented low glass temperature and despite birefringence behavior, these copolymers showed no mesomorphic properties.Keywords: 3,5-disubstituted isoxazolines; copolymers; menthyl acrylate. INTRODUÇÃOCopolímeros são macromoléculas compostas por duas ou mais unidades estruturais diferentes, que podem se distribuir estatisticamente entre si ou de forma a gerar segmentos ou blocos. 1 Podem ser classificados quanto à forma, tendo como base a organização das unidades ao longo da cadeia polimérica, em alternados, periódicos, estatísticos, aleatórios ou em blocos. Também são classificados em lineares ou ramificados, dependendo do arranjo da cadeia polimérica. 2 A reação de copolimerização é uma técnica importante que possibilita modular o polímero, através de modificações sistemá-ticas, agregando propriedades específicas, tornando-o comercial e tecnologicamente mais interessante e vantajoso. 3 Como exemplo, pode-se citar a quitina 4 e seu derivado, a quitosana. Esses são poliaminossacarídeos que têm uma vasta aplicação no campo biomédico. No entanto, esses polímeros naturais mostram algumas desvantagens no uso comercial, por serem insolúveis nos principais solventes utilizados cotidianamente. A fim de superar esse problema pode-se copolimerizar o poliaminossacarídeo com monômeros vinílicos produzindo copolímeros multifuncionais, alterando desta forma as propriedades físico-químicas do polímero natural. Os copolímeros são utilizados de forma bastante diversificada em pervaporação organofílica, 5 formulações para recuperação de óleos terciários, projetos hidráulicos, 6 microgéis inteligentes com aplicação em diversas áreas, tais como transportadores de medicamentos, sensores, separadores químicos e imobilizadores de enzimas. 7 Na área de cristais líquidos, a copolimerização é uma ferramenta importante para preparação de novos materiais que apresentam as propriedades mesogênicas combinadas com as dos materiais poliméricos relacionadas com elasticidade, processabilidade, formação de filmes, confinamento, entre outras. 8 Neste contexto, estamos interessados na síntese e caracterização de novos materiais líquido-cristalinos contendo anéis heterocíclicos, em particular, os anéis "pri...

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Section: Resultsunclassified

Síntese e caracterização de copolímeros de cadeia lateral derivados de acrilatos de 4,5-di-hidroisoxazol e do (-)-mentol

Passo¹,

Merlo²,

Eccher³

et al. 2012

Quím. Nova

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“…and oxime (1 equiv. ) in the presence of NCS in 67% of yield following the experimental procedure according to [23] (Scheme 1c). No mesophase was observed for this isoxazoline (mp.…”

Section: Synthesismentioning

confidence: 99%

“…The initial step was the alkylation reaction of benzaldehyde 1 with a variety of 1-bromoalkanes giving the alkylated products 2 in 90-95% yield [21,23].…”

Section: Synthesismentioning

confidence: 99%

“…The synthesis of the 4-alkyloxybenzaldehydes (2a-d) and the benzaldehyde oximes 3a-d were prepared according to the procedure describe in [23][24][25][26].…”

Section: Synthesis and Characterisationmentioning

confidence: 99%

“…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%

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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

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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An old dog with new tricks: Schiff bases for liquid crystals materials based on isoxazolines and isoxazoles.

Fritsch

Merlo

2016

ChemistrySelect

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Schiff bases are in action again showing an exuberant mesophase range despite their chemical and thermal weakness. Two series of Schiff bases (SB), based on isoxazolines 9 a–f and isoxazoles 10 a–f, are described. 9 a–f were synthesized by a [3+2] cycloaddition 1,3‐dipolar of arylnitrile oxide from p‐nitrobenzaldehyde (1) and alkenes. And, subsequently oxidized to 10 a–f by MnO2. The isoxazolines and isoxazoles thus obtained were reduced to aniline derivatives and condensed with appropriated arylaldehydes. The SBs series isoxazolines 9 a–f presented a narrow mesophase range, while SBs series isoxazoles 10 a–f showed a large mesophase range. Nematic mesophase was observed for SBs with short and non‐polar groups, while SmA and SmC mesophase for SBs with long and more polar terminal groups. The stability of the SBs is also dependent on the clearing temperature. For 10 a–f with high clearing temperature, decomposition induced by heat was observed during the first cycle of heating and in solutions of CDCl3. Series 9 a–f was more resistant to the thermal decomposition.

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Synthesis of liquid-crystalline 3,5-diarylisoxazolines

Cited by 23 publications

References 41 publications

Síntese e caracterização de copolímeros de cadeia lateral derivados de acrilatos de 4,5-di-hidroisoxazol e do (-)-mentol

Síntese e caracterização de copolímeros de cadeia lateral derivados de acrilatos de 4,5-di-hidroisoxazol e do (-)-mentol

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

An old dog with new tricks: Schiff bases for liquid crystals materials based on isoxazolines and isoxazoles.

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