Endo-benzonorbornen-2-ol as an efficient non-natural chiral auxiliary in the asymmetric aza-Diels–Alder reactions between cyclopentadiene and (1-phenylethyl)iminoacetates
作者:Carlos A. D. Sousa、Miguel A. Maestro、Xerardo Garcia-Mera、José E. Rodríguez-Borges
DOI:10.1039/c4ra11143e
日期:——
Exo-2-azabicyclo[2.2.1]hept-5-enes were obtained by cycloaddition reactions between cyclopentadiene and protonated (S)- and (R)-1-phenylethylimines of (1R,endo)-benzonorbornen-2-yl glyoxylate. The non-natural (1R,endo)-benzonorbornen-2-ol proved to be an efficient chiral auxiliary in these asymmetric aza-Diels–Alder reactions, which afforded only exo-cycloadducts with 1S : 1R diastereomeric ratios
通过环戊二烯与(1 R,内)-苯并降冰片烯-2-基乙醛酸酯的质子化的(S)-和(R)-1-苯基乙基亚胺之间的环加成反应获得Exo -2-氮杂双环[2.2.1]庚-5-烯。。非天然(1 - [R ,内切)-benzonorbornen -2-醇证明是在这些不对称氮杂狄尔斯-阿尔德反应,得到仅一个有效的手性助剂外与1 -cycloadducts小号 :1 - [R 15非对映体比率: (S)-(1-苯乙基)亚胺为85,(R为93:7)-(1-苯乙基)亚胺。使用色谱柱可轻松,高效地分离获得的非对映异构体。通过NMR,比旋光度和X射线数据明确地确定了所有形成的加合物的绝对构型。