The use of isoxazoline and isoxazole scaffolding in the design of novel thiourea and amide liquid-crystalline compounds

Itamar L Gonçalves; Rafaela R da Rosa; Vera L Eifler-Lima; Aloir A Merlo

doi:10.3762/bjoc.16.20

The use of isoxazoline and isoxazole scaffolding in the design of novel thiourea and amide liquid-crystalline compounds

Beilstein J Org Chem. 2020 Feb 6:16:175-184. doi: 10.3762/bjoc.16.20. eCollection 2020.

Authors

Itamar L Gonçalves¹, Rafaela R da Rosa², Vera L Eifler-Lima¹, Aloir A Merlo³

Affiliations

¹ Laboratório de Síntese Orgânica Medicinal/LaSOM, Faculdade de Farmácia, Universidade Federal do Rio Grande do Sul, Avenida Ipiranga, Porto Alegre/RS, Brazil.
² CENIMAT/i3N, Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, 2829-516 Caparica, Portugal.
³ Institute of Chemistry, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.

Abstract

A series of novel thiourea and amide liquid crystals containing 5-membered isoxazoline and isoxazole rings were synthetized and the liquid crystal properties studied. Thioureas were obtained using a condensation reaction of benzoyl chlorides, arylamines and ammonium thiocyanate. The amides, on the other hand, were the byproduct of a quantitative reaction which used potassium cyanate as the starting material. Thiourea and amide derivatives were predominantly SmA mesophase inductors. A nematic mesophase was observed only for thioureas and amides containing an isoxazole ring. Additionaly, the liquid crystal behavior was also dependent on the relative position of nitrogen and oxygen atoms on the 5-membered heterocycle.

Keywords: amides; isoxazole; isoxazoline; liquid crystal; thiourea.

Grants and funding

The authors wish to thank the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001 for the fellowships and Conselho Nacional de Pesquisa Científica (CNPq, edital Universal) for the financial support grant n. 403075 2016-5.