3-Arylisoxazolyl-5-carboxylic acid and 5-(Hydroxymethyl)-3-aryl-2-isoxazoline as molecular platforms for liquid-crystalline materials

the synthesis of the molecular platform for liquid-crystalline materials based on 3-arylisoxazolyl-5-carboxylic acid (1) and 5-(hydroxymethyl)-3-aryl-2-isoxazoline (2) is described. the key intermediates 1 and 2 are obtained by [3+2] 1,3-dipolar cycloaddition reaction between an arylnitrile oxide and an acrylic acid and allylic alcohol as the dipolarophile. the liquid crystals (lc) compounds are synthesized through a "molecular elongation strategy" from the initial isoxazolinic core by connecting the arylacetylene moiety obtained from the sonogashira reaction. under these conditions, the series of liquid crystals 5a-c, 6, 7a-g and 8a-d have been successfully synthesized in fair to good yields. the final compounds display nematic and smectic liquid-crystalline properties. the structural properties of the series of the liquid crystals has been studied using dft methods at level b3lyp/6-31g(d,p). the equilibrium geometries in the gas phase are presented and analyzed.