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Abstract
The synthesis and mesomorphic properties of new liquid-crystalline 3,5-disubstituted isoxazolines are presented and discussed. These isoxazoline derivatives have been synthesised by reacting oximes with the appropriate 4-substituted styrene dipolarophiles in the presence of N-chlorosuccinimide and pyridine. The isoxazolines 3a–d and 7a–g prepared by this methodology are used as scaffolds for further molecular derivation through a molecular elongation strategy. The selected scaffolds 3a–b and 7f–g were transformed into liquid crystals (LCs) by the addition of an arylacetylene group at the C3 or C5 carbon atoms on the isoxazoline ring by a Sonogashira reaction. The relevant LC compounds 14a–c, 15, 16, 17 and 18a–c were synthesised in fair to good yields. The final compounds display both nematic and smectic A liquid-crystalline phases.
Acknowledgements
The authors acknowledge Ministério da Ciência e Tecnologia (MCT)/Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) Universal no. 471194/2008-5, MCT/CNPq no. 555785/2006-8, PROCAD-2007-CAPES and INCT-CMN for financial support and Prof. Renato Catalunã for ESI-MS facilities and referees for valuable suggestions and additions to this work. B.C.A. and A.S. are undergraduate students and thank PIBIC-UFRGS for their fellowship.