Recoverable Cinchona ammonium salts as organocatalysts in the enantioselective Michael addition of β-keto esters
作者:Silvia Tarí、Rafael Chinchilla、Carmen Nájera
DOI:10.1016/j.tetasy.2010.11.016
日期:2010.12
Several dimeric Cinchona-alkaloid anthracenyldimethyl-derived ammonium salts, are used as organocatalysts in the enantioselective Michael addition reaction of cyclic β-keto esters to α,β-unsaturated carbonyl compounds, in the presence of diisopropylethylamine as a base (30 mol %), for the generation of enantiomerically enriched adducts bearing quaternary stereocenters. Quinine and quinidine-derived
在二异丙基乙胺为碱(30摩尔%)的情况下,几种二聚Cinchona-生物碱蒽基二甲基蒽盐被用作环状β-酮酯与α,β-不饱和羰基化合物的对映选择性Michael加成反应中的有机催化剂。用于生成带有四级立体中心的对映体富集的加合物。奎宁和奎尼丁衍生的二聚铵盐(1-10 mol%)以较高的收率(最高98%)提供了相应的加合物(最高94%ee)的相反和更高的对映选择性。取代的2-烷氧基羰基-1-茚满酮用作亲核试剂的前体,以及2-氧代环戊烷甲酸乙酯和叔酸乙酯2,5-二氧杂-1-苯基吡咯烷-3-羧酸丁酯。这些有机催化剂可在反应结束时通过在乙醚中沉淀而回收,并在不损失任何活性的情况下重复使用。