Synthesis of maleo- and citraconopimaric acid derivatives with mesogenic groups as chiral dopants to LC-compositions

The method for maleopimaric acid aminoamides synthesis has been developed, which involves the treatment of maleopimaric acid with an excess of thionyl chloride at 18-20 °С and the subsequent reaction of the obtained maleopimaric acid chloride and aromatic diamines (1,4-diaminobenzene, 4,4’-diaminodiphenyl) in 80.5-94.3 % yields. The reaction of maleopimaric acid aminoamides with aliphatic and aromatic aldehydes (isovalerianic aldehyde, benzaldehyde, 4-methoxy-benzaldehyde, 4-chlorobenzaldehyde) gave maleopimaric acid azomethines containing mesogenic groups (4-biphenyl, 4-phe-nylaminobezilidene) in 56.5-99.3 % yields. Maleopimaric and citraconopimaric acid 4-biphenylamides were first synthesized by the reaction of acid chlorides of these acids and 4-aminobiphenyl in yields of 91.3-94.8 %. It was established that the obtained substances are optically active and the specific rotation ([α]D) of the synthesized compounds is -45.0° ÷ -118.2°. It has been shown that the chiral LC phase is formed once the obtained additives (amides and azomethines of maleopimaric acid) are introduced into the nematic liquid crystal matrix (MLC 6809-000, Merck). The helical twisting power of the studied compounds reaches 12.4 pm -1 . The data obtained can be applied in the development of new industrial chiral LC compositions for use in the electronic and LC industry, e.g. TN LCD fabrication.