Combinatorial synthesis of isoxazole library and their liquid crystalline properties

Six types of isoxazoles including 60 molecules were synthesized using combinatorial synthesis on solid support in a parallel fashion. Highly regioselective 1,3-dipolar cycloaddition of the nitrile oxides to the triple bond of the solid-attached ethynylbenzamides gave isoxazoles on solid support in good yield. Thirty molecules of them exhibited mesomorphic properties. The combination of molecular mechanics calculations and X-ray diffraction experiments of 2g and 3g revealed that the smectic phase of 2g had a bilayer structure, whereas 3g showed a monolayer liquid crystalline phase. These are supported in comparison with the single crystal structures of 2g and 3g.