Counteranion-Controlled Unprecedented Diastereo- and Enantioselective Tandem Formal Povarov Reaction for Construction of Bioactive Octahydro-Dipyrroloquinolines

详细信息    查看全文

• 作者：Xiao-Long Yu ; Liping Kuang ; Su Chen ; Xiao-Long Zhu ; Zhong-Liang Li ; Bin Tan ; Xin-Yuan Liu
• 刊名：ACS Catalysis
• 出版年：2016
• 出版时间：September 2, 2016
• 年：2016
• 卷：6
• 期：9
• 页码：6182-6190
• 全文大小：749K
• 年卷期：0
• ISSN：2155-5435

文摘

The asymmetric inverse-electron-demand hetero-Diels–Alder (IEHDA) reactions of imines and dienophiles have emerged as an attractive tool for derivatizing optically active complex azaheterocycles. In comparison, such reactions involving iminium ions remain great challenges because of low association of iminium ions with neutral catalytic centers. To overcome this, we report a metal-phosphate-catalyzed asymmetric tandem hydroamination/formal Povarov reaction of secondary aminoalkynes via a chiral counteranion-controlled iminium ion intermediate strategy. Critical to the success of this challenging strategy was chiral phosphate as an ion pair to achieve counteranion-controlled asymmetric reaction of in situ-generated iminium ions. This method enables a convenient, powerful, and atom-economical access to tetracyclic octahydro-dipyrroloquinoline frameworks bearing multiple contiguous stereogenic centers in good yields with diastereo- and enantioselectivities, from acyclic starting materials, and the catalyst loadings could be as low as 1 mol %. The asymmetric cross-coupling reaction of different aminoalkynes has further been demonstrated with good results. Furthermore, this methodology was applied to enantioselective synthesis of incargranine B aglycone epimer in only two steps. The reaction is demonstrated to proceed through a stepwise process for formal Povarov reaction.