Enantioselective quaternization of 4-substituted oxazol-5-(4H)-ones using recoverable Cinchona-derived dimeric ammonium salts as phase-transfer organocatalysts
作者:Silvia Tarí、Angel Avila、Rafael Chinchilla、Carmen Nájera
DOI:10.1016/j.tetasy.2012.01.012
日期:2012.1
Dimeric anthracenyldimethyl-derived Cinchona ammonium salts are used as chiral organocatalysts (5 mol %) for the enantioselective 4-alkylation of 4-substituted azlactones. The corresponding adducts bearing a new quaternary center were obtained with up to 80% ee when using a dimeric ammonium salt derived from cinchonidine, and are precursors of α,α-disubstituted α-amino acids. The catalysts can be recovered
二聚蒽基二甲基衍生的金鸡纳铵盐被用作手性有机催化剂(5mol%),用于4-取代的内酯的对映选择性4-烷基化。当使用衍生自辛可尼丁的二聚铵盐时,可获得带有新季中心的相应加合物,其ee最高可达80%,它们是α,α-二取代α-氨基酸的前体。通过在乙醚中沉淀几乎可以定量回收催化剂,并可以在不损失活性的情况下重复使用。