Study On Functionalized Ionic Liquids And Their Applications In The Condensation Reactions

Ionic liquids, considered as novel solvents/catalysts compounded functionalized materials, have been widely used in organic reactions because of their unique chemical and physical properties of low melting points, high thermally stability, controlled miscibility, nonvalatility, moderate acidity or alkalescence and so on. Another feature of high pertinence and a wide range of designability of ionic liquids provide a broad space for its sythesis and application. For different reactions, design and preparation of corresponding structure and properties of ionic liquids have become a hot area of current chemistry. To conform to this trend of development, we focused on the design, preparation and application in organic synthesis of ionic liquids, aiming at searching for a series of new functionalized ionic liquids with a value of broad applications, novel structures and high-performances in our dissertation.Firstly, a basic task-specific ionic liquid, 1-butyl-3-methylimidazolium hydroxide [bmim]OH, has been synthesized. It has been introducted as a catalyst for the Knoevenagel condensation reactions of aromatic aldehydes with malononitrile or ethyl cyanoacetat or rhodanine, and the Mannich-type reactions of aromatic aldehydes, cyclohexanone, and aromatic amines. The present protocol offers several advantages, including simple work-up procedure, short reaction time and high yields.Furthermore, ionic liquid [bmim]OH catalyzed three-component condensation reaction of aromatic aldehydes, malononitrile andα-orβ-naphthol proceeded rapidly in water at reflux to afford corresponding 2-amino-2-chromenes in high yields, catalyzed three-component condensation reaction of aromatic aldehydes, malononitrile and active methylene carbonyl compounds for the synthesis of 4H-benzo[b]pyrans at room temperature in aqueous media. In addition, water was chosen as a green solvent. The attractive features of this protocol are simple procedure, mild conditions, short reaction time, excellent yields, mild conditions and the easy workup procedure.Secondly, some acidic ionic liquids that bear imidaolium cation, such as [MIMPS]HSO4, [MIMPS]H2PO4 and [MIMPS]BF4, have been synthesized. And then, the ionic liquid [MIMPS]HSO4 was empolyed as catalyst for the synthesis of 14-alkyl-or aryl-14H-dibenzo[a,j]xanthenes via the one-pot condensation ofβ-naphthol with aliphatic or aromatic aldehydes and the synthesis of 1,8-dioxo-octahydroxanthenes by a one-pot condensation of aromatic aldehydes and active methylene carbonyl compounds. It was indicated that [MIMPS]HSO4 is an efficient, novel and green catalyst. Simultaneously, the synthesis of 1,8-dioxo-octahydroxanthenes in the same reaction conditions was carried out under microwave irradiation. It is an efficient method to reduce reaction time, increase yields and improve selectivity.Lastly, some novel SO3H-functional Br(?)nsted-acidic ionic liquids that bear an alkene sulfonic acid group in acyclic diamine cations have been synthesized via two-step atom economic reactions. The Br(?)nsted acidities of these ionic liquids were evaluated from the determination of the Hammett acidity functions, using UV-visible spectroscopy. Compared with 1-methyl-3-propane sulfonic-imidazolium hydrosulfate [MIMPS][HSO4], the Hammett acidity functions of these ionic liquids are smaller, in other words, the Br(?)nsted acidities of these ionic liquids are stronger. An efficient and direct proceduce has been developed for the preparation of amidoalkyl naphthols by a one-pot condensation of aryl aldehydes,β-naphthol and amides, in the presence of [TMHDAPS][HSO4] as catalyst under solvent-free conditons. Under the optimum conditions as n(aromatic aldehydes):n(β-naphthol):n(amides)=1:1:1.2, and in the presence of 5 mol%, the yields of amidoalkyl naphthols was obtained with 88～98% at 100℃for 6-20 min under solvent-free conditions. This novel synthesis method offers several advantages such as excellent yields, short reaction times and simple procedure. The catalyst could be recycled and reused at least five times without noticeably decrease in catalytic activity.