%0 Journal Article
%T Facile Synthesis of Benzaldehyde-Functionalized Ionic Liquids and Their Flexible Functional Group Transformations
%A Qiang Huang
%A Baozhong Zheng
%J Organic Chemistry International
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/208128
%X Three benzaldehyde-functionalized ionic liquids were readily synthesized by quaternization of N-alkylimidazole with benzaldehyde-functionalized alkyl bromides under microwave irradiation in good yield. These aldehyde-functionalized ionic liquids could easily be oxidized in the presence of H2O2/KOH or be reduced by NaBH4 leading to the formation of the corresponding carboxyl-functionalized ionic liquids or benzylic alcohol-functionalized ionic liquids. In addition, the condensations of these functionalized ones with hydrazine hydrate and with aniline under reductive amination conditions were demonstrated. 1. Introduction Ionic liquids (ILs) have received an increasing interest as green solvent systems in the fields of organic synthesis [1, 2], separation technologies [3], electrochemical devices [4], and materials chemistry [5, 6] because of their advantages over traditional molecular solvents including negligible vapor pressure, broad liquid range, properties modulation, nonflammability, high thermal stability, and so forth [7¨C9]. Recently, the scope of ILs has been expanded by the introduction of additional functional groups in the ionic liquid structure. These so-called task-specific ionic liquids [10] or a much larger family of task-specific onium salts [11] can be utilized as soluble supports for organic synthesis, supported reagents or catalysts [12], and scavengers in solution phase combinatorial synthesis [13, 14] with high affinity for the ionic liquid phase. Task-specific ionic liquids are compatible with a variety of organic transformations and have proven to be useful for the extraction of specific chemicals [15]. The applications of functionalized ILs for the synthesis of inorganic materials have also been reported by several groups in recent years [16, 17]. Aldehyde-functionalized ILs are important and widely used due to their diverse reactivity. They have been used as soluble supports for various organic reactions such as reductive amination [18], Knoevenagel [19], Biginelli [20], and multicomponent reactions [21, 22]. In this work, we report the synthesis of three benzaldehyde-functionalized ionic liquids and their flexible functional group transformations under simple conditions. 2. Results and Discussion 2.1. Synthesis of Benzaldehyde-Functionalized Ionic Liquids The syntheses of N-methylimidazolium based benzaldehyde-functionalized ionic liquids (4a¨Cc) were readily accomplished by alkylation of the phenols (1a¨Cc) with 1,4-dibromobutane (2) and subsequent substitution of benzaldehyde-functionalized alkyl bromides (3a¨Cc) with
%U http://www.hindawi.com/journals/oci/2012/208128/