Synthesis Of Trans-4-(trans-4’-n-propyl-cyclohexyl-yl)-cyclohexyl-vinyl

Now the LCD stands in the mainstream of flat panel display. Mixed liquid crystalmaterial is the main display media in LCD, which plays an irreplaceable role.Trans-4-(trans-4’-n-propyl-cyclohexyl-yl)-cyclohexyl-vinyl(trans-3HHV) has beenwidely applied to the mixed liquid crystal formulations because it has high dielectricconstant, low viscosity, high resistivity, high thermal stability and other characteristicsas the liquid crystal monomer. At present, the synthetic route of3HHV was publiclyreported mostly with the Wittig reaction which was of the low molecular utilization andhigh cost. The two new synthetic routes of3HHV with cis/trans-4-(trans-4’-n-propyl-cyclohexyl)-cyclohexanecarboxylicacid (cis/trans-3HHA) were designed and practiced.First, trans-3HHV was successfully synthesized with trans-3HHA as the startingmaterial via Kochi and coupling reactions, its structure and intermediates wereconfirmed by GC-MS and NMR. Based on the results of condition experiments, theresult of Kochi reaction was best when acetonitrile was as the reaction solvent, thereaction temperature was70～80℃, the ratio of3HHA, Pb(CH3COO)4and LiCl was1:2:1.95(mol/mol/mol). Usd FeCl3as the effective catalyst, the reaction effect of thecoupling reaction was best, the reaction temperature was20～30℃, the ratio of3HHCl, CH2=CH-MgCl, FeCl3and TMEDA was1:2:0.05:2(mol/mol/mol/mol). Themechanism of the coupling reaction was speculated and we thought that the mechanismof the coupling process was the oxidative addition-reductive elimination.Second, using cis/trans-3HHA as the main material, the target product oftrans-3HHV was synthesized via acylation, reduction, isomerization and Wittigreaction. The structure of target product was confirmed by GC-MS, IR, H-NMR and 13C-NMR. According to the results of reaction, the mechanism of reduction wasdiscussed.In the progress of reduction, because the p-π-conjugated group which formedby atom of N and the carbonyl group was played a major role, the reaction of futurereduction was prevented, the product of reduction was the compound of aldehyde. Inaddition to above, we also discussed the mechanism of isomerization and analyzed themechanism and generation progress of the keyimpurity4’-Methylene-4-propyl-bicycloh-exyl(3HHM).Finally, the second route was more suitable for industrial production according tothe final product purity and the process.