Lithium acetate catalyzed aldolreactionbetweentrimethylsilylenolates and aldehydes in a DMF–H2O (50:1) solvent proceeded smoothly to afford the corresponding aldols in good to high yields. It is noted that trimethylsilylenolates derived from carboxylic esters behaved as excellent nucleophiles in the above reaction.
Self-promoted aldolreactionbetweenaldehydes having Lewis base moieties and trimethylsilylenolates proceeded smoothly to afford the corresponding aldols in good to high yields. It is noted that various functionalized aldols can be directly obtained without protection of functional groups in the above reaction.
Chromium-mediated aldol and homoaldol reactions on solid support directed towards an iterative polyol strategy
作者:Ludger A. Wessjohann、Harry Wild、Henri S. Schrekker
DOI:10.1016/j.tetlet.2004.10.038
日期:2004.11
Chromiumn-Reformatsky and chromium-homoaldol reactions run Under neutral and mild reaction conditions. They are highly chemoselective, tolerant towards most common functional groups, and are not prone to retroaldol reactions. Initial studies directed to transfer these homogeneous chromium-mediated solution-phase reactions to solid phase are presented. The main objective was to develop a methodology to aid a combinatorial iterative strategy to polyols (polyketides) on solid phase. A general reactivity problem was observed with polystyrene based resins compared to the solution-phase reactions, independent if the electrophilic (aldehyde) or nucleophilic (bromide) end of the polyol chain was supported to the resin. A complicated penetration, or loss of the polar solvent environment after penetration into the resin, might be responsible for the reduced reactivity. Application of either a soluble polystyrene resin or a polystyrene resin with a polar polyethylene glycol tether resulted in improved yields. (C) 2004 Elsevier Ltd. All rights reserved.
Lithium Acetate-Catalyzed Aldol Reaction between Aldehyde and Trimethylsilyl Enolate in Anhydrous or Water-Containing<i>N</i>,<i>N</i>-Dimethylformamide
AcOLi catalyst, the aldolreaction in water-containing DMF was studied in detail. AcOLi and various metal carboxylates behaved as effective Lewis base catalysts in aldolreactionsbetweentrimethylsilylenolate and aldehydes in DMF-H 2 O (50:1) (Tables 6, 7). One of the most characteristic points of the above reaction that took place in water-containing DMF is that the aldehydes having a free amide
乙酸锂 (AcOLi) 催化的三甲基甲硅烷基烯醇化物和醛之间的醛醇反应在无水 DMF 或吡啶中顺利进行,在弱碱性条件下以良好至高产率提供相应的醛醇(表 1-5)。这种催化羟醛反应也可以通过使用其他金属羧酸盐顺利进行,这些金属羧酸盐通过用碳酸锂 (Li 2 CO 3 ) 处理羧酸很容易原位制备(表 2,方案 5)。为了展示温和易得的AcOLi催化剂的效果,详细研究了含水DMF中的羟醛反应。AcOLi 和各种金属羧酸盐在 DMF-H 2 O (50:1) 中三甲基甲硅烷基烯醇酯和醛之间的羟醛反应中充当有效的路易斯碱催化剂(表 6、7)。在含水DMF中发生的上述反应的最特征点之一是具有游离酰胺和羟基甚至羧基的醛反应平稳并以中等至高产率提供所需的醛醇29-31(表 8,条目 12-15)。由羧酸酯衍生的三甲基甲硅烷基烯醇化物在上述反应中表现得与优异的亲核试剂相似。这是路易斯碱催化醛醇反应的第一个例