Secondary Amine-Catalyzed Asymmetric<i>γ</i>-Alkylation of<i>α</i>-Branched Enals<i>via</i>Dienamine Activation
作者:Mattia Silvi、Carlo Cassani、Antonio Moran、Paolo Melchiorre
DOI:10.1002/hlca.201200412
日期:2012.10
The direct and enantioselective γ‐alkylation of α‐substituted α,β‐unsaturated aldehydes proceeding under dienamine catalysis is described. We have found that the Seebach modification of the diphenyl‐prolinol silyl ether catalyst in combination with saccharin as an acidic additive promotes an SN1 alkylation pathway, while ensuring complete γ‐site selectivity and a high stereocontrol. Theoretical and
描述了在二烯胺催化下进行的α-取代的α,β-不饱和醛的直接和对映选择性的γ-烷基化。我们发现,二苯丙脯氨醇甲硅烷基醚催化剂的Seebach改性与糖精作为酸性添加剂的组合可促进S N 1烷基化途径,同时确保完全的γ。现场选择性高立体声控制。理论和光谱研究为由2-甲基戊-2-烯醛与手性胺缩合衍生的共价二烯胺中间体的构象行为提供了见解。讨论了立体诱导机制的含义。