Enantioselective Cyclopropanation Reactions with Planar-Chiral Pyridinium Ylides: A Substituent Effect and a Remote Steric Effect
作者:Nobuhiro Kanomata、Ryo Sakaguchi、Kazuki Sekine、Satomi Yamashita、Hiroko Tanaka
DOI:10.1002/adsc.201000079
日期:2010.11.22
Novel planar-chiral pyridinium ylides were designed, and generated in situ from the corresponding pyridinium salts with triethylamine. Ylides with a common parapyridinophane skeleton reacted efficiently with electron-deficient dicyanoalkenes, or malononitriles, to produce optically active cyclopropane derivatives with high enantioselectivity (up to 99% ee). Remote steric effects were observed on the
设计了新颖的平面手性吡啶鎓叶立德,并从相应的吡啶鎓盐与三乙胺就地生成。具有常见的对吡啶并吡啶骨架的叶立德与缺电子的二氰基烯烃或丙二腈有效反应,生成具有高对映选择性(最高ee达99%)的旋光性环丙烷衍生物。观察到对映体选择性的空间位阻效应,其中吡啶并吡啶烷核的R 2基团导致产物的ee值更高。密度泛函理论(DFT)的计算与我们的实验结果非常吻合:大力推动的过渡态产生了主要的立体异构体,即反式-环丙烷产品。