Novel planar-chiralpyridiniumylides 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). Remotesteric effects were observed on the
The influence of the Π-electron distribution and Π -bond stability of ketene acetals on their reactivity and stereoselectivity in thermal (2 + 2) cycloadditions with 1,1-dicyanostyrenes
作者:Hans W. Scheeren、Anton J.R. Vas Rossum、Rutger J.F. Nivard