equivalent amount of an organic base leads to high enantiomeric excess in the asymmetric hydrogenation of N‐benzylated 3‐substituted pyridinium salts into the corresponding piperidines. Indeed, in the presence of Et3N, a Rh‐JosiPhos catalyst reduced a range of pyridinium salts with ee values up to 90 %. The role of the base was elucidated with a mechanistic study involving the isolation of the various reaction
在N-
苄基化3-取代的
吡啶鎓盐不对称加
氢成相应的
哌啶中,使用等量的有机碱会导致高对映体过量。实际上,在存在Et 3 N的情况下,Rh‐JosiPhos
催化剂可还原一系列ee值高达90%的
吡啶鎓盐。通过涉及各种反应
中间体的分离和同位素标记实验的机理研究阐明了该碱的作用。另外,该研究为涉及
二氢吡啶中间体的对映体确定步骤提供了一些证据。