Synthesis of 4-alkoxy and 4(4′-alkoxyphenyl)-2,6-di(hydroxymethyl) pyridines and their Applications as Liquid Crystals and Polymer Electrolyte Liquid Crystals

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Abstract
4-Octyloxy-2,6-di(hydroxymethyl)pyridine(2), 4(4′-octyloxyphenyl)-2,6-di(hydroxymethyl)pyridine (4), and 4(4′-octadecyloxyphenyl)-2,6-di(hydroxymethyl)pyridine (3) were synthesised. By modification of a literature method the dimethyl (or ethyl) 4-hydroxypyridine-2,6-dicarboxylate (6) was synthesised with yield greater than 90%, using thionyl chloride/DMF catalyst mixture, compared with 55–85% using methanol or ethanol/H2SO4 mixture as reported in literature. Williamson etherification of (6) using alkyl halide/acetone/K2CO3 mixture gave a poor yield, whereas, in a different synthesis using alkyl halide/toluene/Ag2O mixture, the yield was improved to about 85%. Reduction of the 4-alkoxy-2,6-pyridine dicarboxylate (7) using NaBH4/EtOH or MeOH was found to reduce only one ester and to hydrolyse the other one to acid. Using NaBH4 or LiBH4 THF/MeOH mixture, successfully reduced the diesters (7) and (8). The compounds synthesised were characterized by thermal analysis, FTIR, 1H nmr, and mass spectroscopy. The monomeric diol (3) exhibited both thermotropic and lyotropic (smectic A) behaviour. The polyether prepared from (3) and tetraethylene glycol dichloride gave a smectic A liquid crystal phase when both uncomplexed and complexed with LiBF4 and LiClO4. The complexes were characterized by DSC, small- and wide- angle X-ray diffraction and ionic conductivity -temperature measurements.