Study for the Appearance of Mesogenic Property Induced by Sigmatropic Rearrangement

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Previously, we have prepared monocyclic troponoid liquid crystals, 2-acyloxy-5-alkoxytrpones (1) , which showed monotropic smectic A phases. We could observe an acyl group at C-2 could migrate to the neighboring carbonyl group in liquid crystalline states. I called this migration [1,9] sigmatropic rearrangement.In this project, I jntended that dynamic molecular rearrangement would induce the exhibition of the mesogenic properties. When we prepared 5-acyloxy-2-alkoxytropones (2) , in which the substituents on C-2 and C-5 of 1 were replaced, 2 were not mesogenic. We could determine, however, virtual transition temperatures by extrapolation of the binary phase diagram between 2 and the reference compounds, which has a smectic A phase. The virtual transition temperatures were similar to the transition tenperatures of 1, but their melting points were higher than 1. Therefore, we could conclude that [1,9] sigmatropy reduced melting points.Next, in order to prepare monocyclic troponoid liquid crystals with higher thermal stability, we introduced fluorine atoms into the alkyl chains to synthesis enantiotropic liquid crystals with monocyclic troponoids. Furthermore, we extended to prepare enantiotropic liquid crystals with 2,5-dialkoxytropone structure with fluorine atoms in the side chains.