Application Of Cupric And Ferric Catalyzed Grignard Reagent Cross-Coupling Reaction In The Synthesis Of Liquid Crystal Materials

Liquid crystal display has already become the mainstream technology of current flat display. The liquid crystal materials for display are boosted by the boom in the development of liquid crystal display technology. This paper briefly introduced the development of liquid crystal materials for display and the structure characteristic of liquid crystal molecule, some disadvantage in synthesis of liquid crystal materials were analyzed, they were solved by applied study on cupric and ferric catalyzed Grignard reagent cross-coupling reaction in synthesis of liquid crystal materials, the traditional synthesis procedures were simplified, the cost was economized, atom economy and synthetic yields were increased, the environmental pollution in synthesis process was decreased, the methods were more sustainable, and the mechanism of Grignard reagent cross-coupling reaction was analysed in brief. The main work of this paper was as follows:1- bromo- 4- alkyl- cyclohexanes and 1- bromo- 4- trans- alkyl-bicyclohexanes were important liquid crystal intermediates, whose synthesis methods has never been reported to the best of our knowledge. In this paper, the preparation ways and the influence factors were studied, reasonable reaction conditions were confirmed, the yields were about 85%, three 1-bromo-4-alkyl-cyclohexane compounds and three 1-bromo-4-alkyl-trans-bicyclohexane compounds were prepared, a key problem which in applying Grignard reagent cross-coupling reaction for synthesis of trans-alkyl-cyclohexyl benzene series liquid crystal compounds was solved.The C-C bonds cross-coupling reactions of aromatic Grignard reagents with primary and secondary alkyl halides catalyzed by economic and ecofriendly transition metal chlorides were studied, the effect of various factors and different catalysts on these reactions were discussed, and the appropriate reaction conditions were obtained.The synthesis way of trans-alkyl-cyclohexyl benzene series liquid crystal was improved on by anhydrous ferric chloride catalyzed procedure to couple secondary alkyl bromides with aromatic Grignard reagents, the five processes were reduced to two processes, total yield was increased from 25%～35% to 55%～70%, and 9 trans-alkyl-cyclohexyl benzene series liquid crystal compounds were prepared.The synthesis way of alkyl-biphenyl series liquid crystal intermediates was improved on by anhydrous cupric chloride catalyzed procedure to couple primary alkyl bromides with aromatic Grignard reagents, the four processes were reduced to two processes, total yield was increased from 35% to 75% more or less, 9 alkyl-biphenyls were synthesized, and 5 of which were prepared into alkyl-biphenyl-cyanogen series liquid crystal compounds.All prepared compounds were tested by GC, melting points of solid products were tested, and the molecule structures were identified by IR, 1H NMR and MS, several important compounds were identified by elemental analysis, the liquid crystal phase states of liquid crystal compounds were confirmed by DSC.