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

作者：Fritsch Luma; Merlo Aloir A^*

来源：ChemistrySelect, 2016, 1(1): 23-30.

DOI：10.1002/slct.201500044

• Liquid Crystal
• Schiff Base
• Isoxazoline
• Isoxazole
• [3+2] 1,3-dipolar Cycloaddition

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 9a-f and isoxazoles 10a-f, are described. 9a-f were synthesized by a [3+2] cycloaddition 1,3-dipolar of arylnitrile oxide from p-nitrobenzaldehyde (1) and alkenes. And, subsequently oxidized to 10a-f by MnO2. The isoxazolines and isoxazoles thus obtained were reduced to aniline derivatives and condensed with appropriated arylaldehydes. The SBs series isoxazolines 9a-f presented a narrow mesophase range, while SBs series isoxazoles 10a-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 10a-f with high clearing temperature, decomposition induced by heat was observed during the first cycle of heating and in solutions of CDCl3. Series 9a-f was more resistant to the thermal decomposition.

• 出版日期2016-1