Construction of Contiguous Tetrasubstituted Carbon Stereocenters by Intramolecular Crossed Benzoin Reactions Catalyzed by N-Heterocyclic Carbene (NHC) Organocatalyst
作者:Tadashi Ema、Kumiko Akihara、Ryoko Obayashi、Takashi Sakai
DOI:10.1002/adsc.201200499
日期:2012.11.26
Bicyclic compounds with two contiguous tetrasubstituted carbon stereocenters at bridgehead positions were synthesized by N-heterocyclic carbene (NHC)-catalyzed intramolecular crossed benzoin reactions of symmetrical compounds. This desymmetrization strategy was applied to asymmetric synthesis with chiral NHC organocatalysts. Transition-state models were proposed to explain the enantioselectivity. A
通过N-杂环卡宾(NHC)催化对称化合物的分子内交叉安息香反应,合成了在桥头位置具有两个连续四取代碳立体中心的双环化合物。这种去对称化策略被应用于手性NHC有机催化剂的不对称合成。提出了过渡态模型来解释对映选择性。通过逐步策略合成了具有三个连续的四取代碳立体中心的三环化合物。通过X射线晶体学分析确定该三环化合物的(+)-对映异构体的分子结构和绝对构型。