Halogenation of Carbonyl Compounds by an Ionic Liquid, [AcMIm]X, and Ceric Ammonium Nitrate (CAN)
作者:Brindaban C. Ranu、Laksmikanta Adak、Subhash Banerjee
DOI:10.1071/ch07061
日期:——
An ionic liquid, acetylmethylimidazolium halide ([AcMIm]X), in combination with ceric ammoniumnitrate promotes halogenations of a wide variety of ketones and 1,3-keto esters at the α-position. The ionic liquid acts here as reagent as well as reaction medium, and thus the reaction does not require any organic solvent or conventional halogenating agent. The reaction is completely arrested when the radical
离子液体乙酰甲基咪唑鎓卤化物 ([AcMIm]X) 与硝酸铈铵结合可促进多种酮和 1,3-酮酯在 α 位的卤化。离子液体在此既充当试剂又充当反应介质,因此该反应不需要任何有机溶剂或常规卤化剂。当使用自由基猝灭剂 TEMPO 时,反应完全停止。还提出了一种似是而非的激进机制。
Trifluoromethanesulfonic Anhydride-Promoted .ALPHA.-Bromination of Ketones with Grignard Reagent or Magnesium Bromide.
The direct alpha-bromination of various ketones using trifluoromethanesulfonic anhydride and Grignardreagent or magnesium bromide in ether gave the corresponding alpha-bromo ketones in moderate to good yields under mild reaction conditions.
Cyclic ketones reacted with N-bromosuccinimide (NBS) catalysed by NH4OAc in Et2O at 25 °C to give the corresponding α-brominated ketones in good yields, while acyclic ketones were efficiently brominated in CCl4 at 80 °C.
Room temperature ionic liquids (ILs) are used as a green recyclable reaction media for the α-monohalogenation of 1,3-diketones, β-keto-esters and cyclic ketones with N-halosuccinimides in excellent yields in the absence of a catalyst. The recovered ionic liquid was reused five to six times with consistent activity.
A simple and efficient method for α-bromination of carbonyl compounds using N-bromosuccinimide in the presence of silica-supported sodium hydrogen sulfate as a heterogeneous catalyst
α-Bromination of carbonyl compounds (cyclic and acyclic ketones, amides and β-ketoesters) has been achieved efficiently by treatment with N-bromosuccinimide (NBS) and catalyzed by silica-supportedsodiumhydrogensulfate (NaHSO4·SiO2). The products were formed in high yields under mild reaction conditions and in short reaction times.