Synthetic pathway for a new series of liquid crystal 2,6-disubstituted imidazo[2,1-b][1,3,4]thiadiazole

Abstract

Herein, the synthesis of a novel series of liquid crystals 2,6-disubstituted imidazo[2,1-b]-1,3,4-thiadiazoles derivate is reported. These fused heterocyclic compounds were prepared through the cyclodehydration between 5-substituted-1,3,4-thiadiazole-2-amino derivatives and α-bromo aryl ketones. The derivates of 2-amino-thiadiazole were obtained from the condensation reaction between thiosemicarbazide and aryl/alkyl nitriles with good yields (60–83%). The α-bromination of aryl ketones was carried out using NBS as the source of electrophilic bromine, also with good yields (52–85%). For the final compounds, the liquid crystal behaviour was shown to be dependent on the number of chains. Mesomorphism was not observed for compounds without aliphatic chains, with more than two aliphatic chains or when the aliphatic chains are methoxy groups.

Keywords:

• synthesis
• X-ray diffraction
• α-bromo arylketones
• imidazo[2,1-b]-1,3,4-thiadiazole
• 2-amino-1,3,4-thiadiazole

Acknowledgements

The authors are grateful to the following institutions for financial support: CNPq, CAPES/PNPD, INCT-cat, PRONEX/FAPESC and INCT/INEO. The X-ray diffraction experiments were performed at the Laboratório de Difração de Raios-X (LDRX-DF/UFSC).