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
DOI:10.1016/s0040-4020(01)91903-9
日期:1983.1
Enantioselective cyclopropanation reaction using a conformationally fixed pyridinium ylide through a cation–π interaction
作者:Shinji Yamada、Jun Yamamoto、Emiko Ohta
DOI:10.1016/j.tetlet.2006.11.142
日期:2007.1
Using a chiral pyridinium ylide with a fixed conformation through a cation-pi interaction performs enantioselective cyclo-propanation of electron-deficient olefins. H-1 NMR, X-ray structural analysis and DFT calculations elucidated the self-complexation and the face-to-face arrangement between the pyridinium and the phenyl rings. The absolute configuration of the product was determined after conversion into a bicyclic cyclopropane derivative. (c) 2006 Elsevier Ltd. All rights reserved.