Formamides derived from N-methyl amino acids serve as new chiral organocatalysts in the enantioselective reduction of aromatic ketimines with trichlorosilane
作者:Andrei V. Malkov、Sigitas Stončius、Kenneth N. MacDougall、Andrea Mariani、Grant D. McGeoch、Pavel Kočovský
DOI:10.1016/j.tet.2005.08.117
日期:2006.1
Asymmetric reduction of N-aryl ketimines 1a–k, 43, and 45 with trichlorosilane can be catalyzed by new N-methyl l-amino acid-derived Lewis-basic organocatalysts, such as the valine-derived bisamide 3d (10 mol%), in toluene at room temperature with high enantioselectivity (≤92% ee). The structure–reactivity investigation shows that the product configuration is controlled by the nature of the side chain
N-芳基酮亚胺1a - k,43和45用三氯硅烷的不对称还原可以由新的N-甲基l-氨基酸衍生的Lewis碱性有机催化剂催化,例如缬氨酸衍生的双酰胺3d(10 mol%),在室温下在甲苯中具有高对映选择性(≤92%ee)。结构反应研究表明,产物构型受催化剂支架侧链性质的控制(例如,在3d和6e中,i -Pr vs Me)),因此相同绝对构型的催化剂可能会诱导产物相反的对映异构体的形成。催化剂与传入的亚胺之间的芳烃-芳烃相互作用似乎是不对称诱导的前提。这种无金属的有机催化方案与传统的金属催化方法相比具有竞争优势。