polystyrene-supported L-proline material is reported, and this material has been used as catalyst in direct asymmetric aldol reactions between several ketones and arylaldehydes to furnish aldol products in high yields and stereoselectivities. Screening of solvents showed that these reactions take place only in the presence of water or methanol, at lower levels of conversion in the latter case. This solvent effect
报道了一种制备聚
苯乙烯负载的
L-脯氨酸材料的简单合成方法,该材料已用作几种酮和芳醛之间直接不对称醛醇反应的催化剂,以提供高产率和立体选择性的醛醇产物。溶剂筛选表明,这些反应仅在
水或
甲醇存在下发生,在后一种情况下转化率较低。这种溶剂效应与观察到的高立体选择性相结合,可以通过在
树脂内表面形成疏
水核来解释,而亲
水脯
氨酸部分位于
树脂/
水界面。这种微环境既促进了羟醛反应又增加了立体选择性。回收研究表明,这种材料可以重复使用,而不会降低转化率和立体选择性,至少可以使用五个循环。(© Wiley-
VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)