way of intramolecular cation–π complex formation enabled nucleophiles to attack the pyridinium ring from the non-shielded side. As a result, 1,2- and 1,4-dihydropyridines were formed in good stereoselectivities. 1H NMR analysis and ab initio calculations at the RHF/3-21G* level supported the existence of cation–π interaction between the pyridinium and the aromatic ring of the chiral auxiliary.
通过分子内阳离子-π络合物的形成对
吡啶鎓表面的一侧进行选择性屏蔽,使亲核试剂能够从非屏蔽的一侧攻击
吡啶鎓环。结果,形成了具有良好立体选择性的1,2-和1,4-
二氢吡啶。RHF / 3-21G *
水平的1 H NMR分析和从头算计算支持
吡啶鎓与手性助剂芳环之间存在阳离子-π相互作用。