Sonogashira coupling applied in the synthesis of 1,2,4-oxadiazole-based nonsymmetrical liquid crystals

A series of highly pi-conjugated nonsymmetrical liquid crystals, based on the core 3,5-(disubstituted)-1,2,4-oxadiazole with a shape similar to a hockey stick, were successfully synthesized by convergent Sonogashira coupling reaction between the building blocks of aryl iodides and the corresponding terminal arylacetylenes, using 3-[4-(decyloxy)phenyl]-5-(haloaryl)-1,2,4-oxadiazoles or decyl 4-iodobenzoate (10) and terminal arylacetylenes. This versatile synthetic route yielded luminescent mesogens with smectic and nematic phases, typical of calamitic compounds.