Synthesis and mesomorphic properties of naphthyl propionate ferroelectric liquid crystals

Ferroelectric liquid crystalline compounds containing (2S)-2-(6-hydroxy-2-naphthyl)propionic acid moiety were synthesized from (S)-naproxen (1). Reactions of (S)-naproxen chloride with alkanols (C-4-C-6) in the presence of propylene oxide gave chiral esters 4. Demethylation of 4 with dimethylsulfide-AlCl3 produced naphthols 5 . Esterfication of naphthols 5 with 4-(4-alkoxyphenyl)benzoic acid 6 using 1,3-dicyclohexylcarbodiimide and 4-dimethylaminopyridine afforded alkyl (S)-2-{6-[4-(4'-alkoxyphenyl)benzoyloxy]-2-naphthyl} propionates 7 in good yields. Naphthyl propionates 9 having a fluorine substituent on the biphenyl core were similarily prepared. HPLC analysis using chiral column confirmed that racemizations did not occur in all processes. All of the optically pure naphthyl propionate compounds 7 and 9 showed an enantiotropic mesomorphic phase. Some derivatives of 7 and 9 with a straight terminal chain attached to the external side of the chiral center exhibited blue phase (BP) and/or twist grain boundary (TGB(A)) phase.