On the origins of diastereoselectivity in the conjugate additions of the antipodes of lithium N-benzyl-(N-α-methylbenzyl)amide to enantiopure cis- and trans-dioxolane containing α,β-unsaturated esters
作者:Stephen G. Davies、Emma M. Foster、Aileen B. Frost、James A. Lee、Paul M. Roberts、James E. Thomson
DOI:10.1039/c2ob25099c
日期:——
“Matching” and “mismatching” effects in the doubly diastereoselective conjugate additions of the antipodes of lithium N-benzyl-(N-α-methylbenzyl)amide to enantiopure cis- and trans-dioxolane containing α,β-unsaturated esters have been investigated. High levels of substrate control were established first upon conjugate addition of achiral lithium N-benzyl-N-isopropylamide to both tert-butyl (S,S,E)-4
“匹配”和在锂的对映体的非对映选择性双重共轭加成“失配”效应Ñ苄基(Ñ -α甲基苄基)酰胺对映体纯的顺式-和反式二氧戊环已经研究了含有α,β-不饱和酯的化合物。首先将非手性N-苄基-N-异丙酰胺锂共轭加到叔丁基(S,S,E)-4,5- O-异亚丙基-4,5-二羟基己基-2-基上建立高水平的底物控制烯酸酯和叔丁基(4 R,5 S,E)-4,5 - O-异亚丙基-4,5-二羟基己-2-烯酸酯。然而,在共轭添加锂(R)-N-苄基-(N -α-甲基苄基)酰胺和锂(S)-时,N-苄基-(N -α-甲基苄基)酰胺对这些底物的反应配对均不能增强底物控制的明显意义。因此,这些反应不符合此类反应通常表现出的经典的双非对映选择性“匹配”或“不匹配”模式。还讨论了这些反应与以前报道的锂酰胺试剂对类似底物的双非对映选择性共轭加成反应的比较。