Synthesis Of Nitrogen Heterocyclic Compounds Through Aldehydic-amide Condensation Reaction Catalyzed By Ionic Liquids

Nitrogen heterocyclic compounds are an important type of heterocycles in organic chemistry, and widely applied in many fields, such as chemical industry, medicant, biology and so on, so there are great significances to study on the synthesis of them. Currently, catalysts and solvents used in the synthesis of heterocyclic compounds are mainly some volatile toxic agents and strong corrosive inorganic acids, which severely pollute the environment. The rapid development of ionic liquids (ILs) makes it not only be used as an effective solvent, but also act as a green and efficient reusable catalyst to promote the synthesis of heterocyclic compounds. A series of ILs were prepared in this paper, and used for condensation reaction of aldehyde and amine to synthesize heterocyclic compounds.A novel acidic IL, 1-dodecyl-3-(3-sulfopropyl)-imidazolium hydrogen sulfate [C3SO3HDoim]HSO4, was designed, synthesized, and characterized by 1H NMR,13C NMR, IR, MS, Elemental Analysis, to achieve yield of 83.9%. Applications of several ILs that bear group in imidazolium cation, caprolactam cation, or tetra-alkyl-ammonium cation in the synthesis of heterocyclic compounds, such as tetrahydroimidazo[4,5-d]imidazole-e-2,5-(1H,3H)-dione (glycoluril),2,5,7,9-tetrazobicyclo[4.3.0]nonan-8-one and hexabenzylhexaazaisowurtzitane (HBIW), were studied. It was found that [C3SO3HDoim]HSO4 had the best catalytic performance and high cyclic utilization reusability, and the possible reaction mechanisms were also proposed. Under the optimized reaction conditions, the yields of three kinds of multi-nitrogen heterocyclic compounds glycoluril, 2,5,7,9-tetrazobicyclo[4.3.0]nonan-8-one and HBIW, could reach 95%,89% and 81% respectively.Five kinds of acidic ILs were prepared and used for Biginelli-type condensation reaction among aromatic aldehydes, urea or thiourea and cyclopentanone. Through this reaction, the synthesis of various pyrimidinones could be achieved. Of interest, it was found that the reaction was efficiently catalyzed by [C3S03HDoim]HSO4, which could be reused for at least 7 times without significantly loss of catalytic activity. Under the optimized reaction conditions, with the ratio of benzaldehyde, urea and cyclopentanone being 2:1:1, the loading of ILs being 10 mol% (relative to aromatic aldehyde), the reaction proceeded efficiently to afford the desired products in good yields (80% to 96%). In addition, a possible mechanism that accounted for the ILs-catalyzed reaction was proposed.In the thesis, four kinds of imidazole-type ILs [EMIM][BF4], [BMIM][BF4], [EMIM][PF6], [BMIM][PF6], were prepared to catalyze the synthesis of three heterocyclic compounds. The result showed that [BMIM][PF6] had the best catalytic properties to obtain 1,4,6,9-tetrazabicyclo[4.4.0]decane with yield of 93% under the optimized conditions; application of [BMIM][BF4] in the synthesis of 2,4,7,9,11,14-hexazatricyclo[8.4.0.03,8] tetradecane was invested and the yield was up to 63%; 2-phenyl benzimidazole with yield of 98% was synthesized via ultrasonic irradiation-assisted condensation of o-phenylenediamine and benzaldehyde using [BMIM][PF6] as catalyst. At last, possible mechanisms that accounted for the ILs above catalyzed reactions were proposed and the cyclic utilization reusability of the ILs was also studied.