Green chemistry approach to the synthesis of liquid crystalline materials

Abstract

This article presents a simple, rapid, economic and environmentally acceptable microwave promoted “green chemistry” approach to the synthesis of some conventional and non-conventional liquid crystalline materials. Alkylation of 4'-hydroxy-4-biphenylcarbonitrile with various alkyl halides under microwave irradiation furnished alkoxycynobiphenyl-based calamitic liquid crystals in very high yield within one minute. Similarly, terminally-functionalized alkoxycyanobiphenyls and alkoxycyanobiphenyl dimers can also be prepared. Microwave irradiation of hexaalkoxytriphenylene in the presence of ionic liquids gives monohydroxy-pentaalkoxytriphenylene in about 30% yield. Novel imidazolium-based ionic liquid crystalline dimers can be easily prepared via quaternization reaction using microwaves. Classical reaction conditions failed to produce these dimers.