Synthesis of new liquid-crystalline compounds from the 3-aryl-5-alkylpyrazole series

A method was developed for the preparation of new liquid-crystalline substances, pyrazole derivatives, through the corresponding 2-isoxazolines and isoxazoles. The hydrogenolysis of the heterocycle in 3-(4-hydroxyphenyl)-5-amylisoxazole afforded 1-amino- 1-(4-hydroxyphenyl)-1-octen-3-one. The acid hydrolysis of the compound followed by treating with hydrazine hydrate resulted in 5-amyl-3-(4-hydroxyphenyl)-1H-pyrazole, whose benzylation and esterification with the corresponding mesogenous benzyl chlorides and benzoyl chlorides provided liquid-crystalline 5-alkyl-3-aryl-1H-pyrazoles.