54676-92-5Relevant academic research and scientific papers
Counteranion-Controlled Unprecedented Diastereo- and Enantioselective Tandem Formal Povarov Reaction for Construction of Bioactive Octahydro-Dipyrroloquinolines
Yu, Xiao-Long,Kuang, Liping,Chen, Su,Zhu, Xiao-Long,Li, Zhong-Liang,Tan, Bin,Liu, Xin-Yuan
, p. 6182 - 6190 (2016)
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.
