Study On Applications Of Ionic Liquids In Multicomponent Condensation Reactions

In recent times, room temperature ionic liquids have been widely applied in organic synthesis because of their unique properties such as non-volatility, non-inflammability, tunable acidity and alkaline, wide liquid range, good solvating ability, high chemical and thermal stability and recyclable. Multicomponent reaction is a highly efficient and green synthesis pathway, which includes excellent synthesis efficiency, simple procedure, structural diversity, environmentally friendly, atom economy and closer to the ideal synthesis. In this paper, with the view of green chemistry, a varity of heterocyclic compounds which posses important biological and pharmaceutical activities were designed and synthesized using ionic liquids as green catalyst or reaction medium through multicomponent reaction. The main contents as follow:Firstly, the definition, development, types, properties and synthesis of ionic liquids and the conception, development, feature and the advantages in the synthesis of multicomponent reaction were introduced. And the applications of ionic liquids in multicomponent organic synthesis reactions were simply reviewed in recent years.Secondly, Biginelli reaction of aromatic aldehydes, 1,3-dicarbonyl compounds and urea or thiourea and three-component condesation reaction of aldehydes, cyclic 1,3-dicarbonyl compounds, andβ-naphthol were investigated using inexpensive and simple acidic ionic liquid [Hnmp]HSO4 as catalyst under solvent-free conventional heating condictions, and four-component Hantzsch reaction of aldehydes, 5,5-dimethyl-1,3-cyclohexanedione, acetoacetanilide and ammonium acetate were also studied in ethanol in the presence of [Hnmp]HSO4. The applications of ionic liquid [Hnmp]HSO4 in above multicomponent reactions, which avoids the toxic fluorine containing ionic liquids and expensive imidazole or propyl sulfonic acid ionic liquids, provides an efficient, fast and environmentally friendly new procedure for the preparation of tetrahydrobenzo[a]xanthen-11-one derivatives, and extends the application scopes of Hantzsch reaction and enriches hexahydroquinoline compound libraries.Lastly, 2-amino-4-aryl-4H,5H-pyrano[3,2-c]benzopyran-5-one derivatives were synthesized via three-component condensation reactions of aromatic aldehydes, 4-hydroxycoumarin and malononitrile in the presence of alkaline ionic liquid 2-hydroxyethylammonium acetate (HEAA) as catalyst in ethanol at room temperature. The method has several advantages such as simple operational procedure, mild reaction condition, short reaction time, high yields and the catalyst could be reused, which is much valuable in industrial applications.Multicomponent reactions were catalyzed by ionic liquids in the above mentioned methods, which offers several advantages such as simple operational procedure, high yields, short reaction time, recyclability of the ionic liquids and environmentally friendly. These methods meet the green chemistry and have potential applications.