Application Of Ionic Liquid In Dimerization Of A-Methylstyrene, Cleavage Of Acetals (Ketals) And Asymmetric Epoxidation Catalyzed By Chiral Ketones

In this dissertation, the application of ionic liquids in three types of organic reaction was studied. The reactions includes dimerization of the a-methylstyrene (AMS), deprotection of acetals(ketals) and asymmetric epoxidation catalyzed by chiral ketones.1. Dimerization of a-methylstyrene (AMS) catalyzed by acidic ionic liquid [Hmim]+ BF₄ -.( 1 ) 2,4-Diphenyl-4-methyl-l-pentene (1-PT) was produced selectively by dimerization of AMS with catalytic amount of ionic liquid [Hmim]⁺ BF₄ -. With respect to the dimerization rate and selectivity to the desired 1-PT, the reaction conditions were optimized. Higher selectivity and good conversion were obtained at 60°C when the molar ratio of ionic liquid to AMS was 1/2. The selectivity for 1-PT was 92.4%, and the conversion was up to 97.0%.( 2 ) The catalytic effect of [Hmim]⁺BF₄ - was compared with [HSO₃Bumim]⁺CF₃SO₃ -. The results showed that [Hmim]⁺BF₄ - gave higher selectivities, and [HSO₃Bumim]⁺CF₃SO₃ - gave higher reaction rate.( 3 ) The recycle of the ionic liquid [Hmim]⁺BF₄ - was also investigated. [Hmim]⁺BF₄ - could be. reused all the times without loss of activity and selectivity for 1-PT if 10% of catalyst was added after the reaction.2. Deprotection of acetals and ketals in Br0nsted acidic ionic liquid An efficient method for deprotection of acetals and ketals was developed with the Br0nsted acidic ionic liquid [Hmim]⁺BF₄ - as catalyst as well as solvent.The deprotection of aromatic ethylidene-acetals and ethylene ketals was carried out with satisfactory conversion (61.9%-100%) and selectivity (51.9%-100%) at 90°C in [Hmim]⁺BF₄/H₂O (l:l,v/v). Better results were obtained for cyclic ketals. Compared to acetals of cyclohexanone, acetals of cyclopentanones gave more satisfactory results. Asto the aromatic acetals, 4-nitrobenzaldehyde, the one with electron withdrawing groups, gave 100% of conversion with 83.9% of selectivity.3. Synthesis of chiral ketones and application to the asymmetric epoxidation of cinnamyl alcohol in ionic liquids.(1) Serveral sugar-derived ketones were designed, and four of them were synthesized using D-fructose and glucose as starting materials.(2) The asymmetric epoxidation of cinnamyl alcohol catalyzed by the chiral ketones was carried out in two neutral ionic liquids [Bmim]⁺Br^- and [Bmim]BF₄ -. The preliminary test indicated that the asymmetric epoxidation of cinnamyl alcohol could be proceed in [Bmim]⁺BF₄/H₂O (1:2, v/v) at 0 °C with 40% yield and 43% ee.(3) The solvent and temperature effect of asymmetric epoxidation catalyzed by chiral ketones were also tested. The configuration of the epoxide was reversed when using [Bmim]⁺Br - as solvent. The reaction was accelerated while promoting temperature, however, the by-product was also increased.