Synthesis and Liquid Crystal Properties of New Fluorinated Isoxazoles

New fluorinated LC 3,5-diarylisoxazolines and 3,5-diarylisoxazoles have been synthesized and their thermal properties reported. Isoxazolines were synthesized using [3+2] 1,3-dipolar cycloaddition from nitrile oxide and alkenes with subsequent MnO2-oxidation yielded the corresponding isoxazoles. The title compounds obtained were characterized by H-1 and C-13 NMR, differential scanning calorimetry (DSC), elemental analysis and polarized optical microscopy (POM). The final compounds are composed by terminal flexible hydrogenated alkyl chains or semiperfluoroalkyl chains. 3,5-diarylisoxazoline composed of alkyl chains is not LC, whereas when composed of one or two semiperfluoroalkyl chains it displays SmA mesophase. For 3,5-diarylisoxazoles a second mesophase SmC was also observed.