Selective Cyclodimerization and Cyclotrimerization of Acetals Bearing Electron-Withdrawing Groups Catalyzed by Lewis Acids
作者:Sayuki Maeda、Yasushi Obora、Yasutaka Ishii
DOI:10.1002/ejoc.200900432
日期:2009.8
of acetals with active methylene compounds. From 4,4-dimethoxy-2-butanone, however, 1,3,5-triacetylbenzene, which is difficult to prepare regioselectively by conventional methods, was formed in quantitative yield under the influence of AlCl3. This reaction would provide a very convenient route to 1,3,5-triacetylbenzene. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
发现缩醛如带有吸电子基团的 3,3-二乙氧基丙酸酯在路易斯酸存在下发生环二聚和环三聚,得到香豆酸盐和 1,3,5-三取代苯。这些产品的选择性取决于所用的路易斯酸。例如,在FeCl3等d-嵌段路易斯酸的影响下,从3,3-二乙氧基丙酸乙酯以高选择性获得香豆酸乙酯,而在镧系元素的影响下,优先于香豆酸乙酯获得1,3,5-苯三甲酸乙酯路易斯酸,如 GdCl3。通过 FeCl3 催化的缩醛与活性亚甲基化合物的交叉环二聚反应合成了各种香豆酸盐。然而,从 4,4-二甲氧基-2-丁酮,1,3,5-三乙酰苯,很难通过常规方法区域选择性地制备,在 AlCl3 的影响下以定量收率形成。该反应将为 1,3,5-三乙酰苯提供一条非常方便的路线。(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)