Synthesis Of A Novel Chiral Imidazolium Salt, Preparation Of Imidazolium Based Ionic Liquids And Their Application In Catalytic Benzoin Condensations

As an important starting material, intermediate or a key additive, benzoin has wide applications in organic syntheses and in some industries. Study on benzoin's convenient and efficient preparative methods that friendly to the surroundings is meaningful. In this thesis, an emphasis is on the synthesis of a novel chiral imidazolium salt, preparation of a series of imidazolium based ionic liquids and also their application in catalytic benzoin condensations.A novel chiral bis-imidazole compound and its azolium derivative have been synthesized. The single crystal of the important intermediate chiral bis-imidazole compound (-)-l,4-di(N-imidazolyl)-2,3-O-isopropylidene-L-threitol has been obtained. The ability of the chiral bis-imidazolium salt for asymmetric catalytic benzoin condensation has been probed. It has shown good catalytic activity for benzoin condensation, but no enantioselectivity has been detected.The structures of the important intermediates and the desired products have been identified by MS, 1HNMR etc.Benzoin condensation using imidazolium based ionic liquids as solvent for the first time has been successfully achieved. The reaction conditions have been studied in detail. When under 65 and with 0.5 equiv. NaOH in ionic liquid l-butyl-3-methyl-imidazolium tetraborate, benzoin was obtained in excellent yield of 91%. Recycling of ionic liquid has been available. Furthermore, self-condensations of a series of representative substituted benzaldehydes in ionic liquid have been investigated and moderate or higher yields have been obtained.