| 摘要 |
NEW MATERIAL:A compound expressed by formula I (R is 1-15C alkyl or alkoxy; X is formula II, phenylene, formula III, IV or V or biphenylene; Y is F or Cl). EXAMPLE:2-(4'-Ethylphenyl)-5-cyano-6-chloropyridine. USE:One component of a liquid crystal composition, which is a liquid crystal compound having high positive dielectric anisotropy and improved compatibility with other liquid crystal compounds, and capable of reducing the driving voltage of liquid crystal display elements. PREPARATION:A sodium phenolate of a formylacetone derivative obtained from a trans-4-substituted cyclohexyl methyl ketone or 4-substituted acetophenone expressed by formula VI and a formic acid ester is condensed with cyanoacetamide in an aqueous solution to give a compound expressed by formula VII, which is then reacted with POCl3 to afford the compound expressed by formula I (Y is Cl). The resultant compound is further subjected to the halogen exchange with KF to give the compound expressed by formula I (Y is F).
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