Construction of Multiring Frameworks by Metal-Free Cascade Reactions of Stable Isochromenylium Tetrafluoroborate

摘要

Efficient methodologies for constructing several multiring frameworks have been developed utilizing thecascade reactions of air-stable isochromenylium tetrafluoroborates with olefins. Successive additions of twoequivalents of styrene-type olefins to isochromenylium tetrafluoroborate (ICFE) I have been observed andtheir mechanisms were proposed and discussed. Intramolecular capture of the early stage cationic intermediatesby predevised heteroatoms or Friedel-Crafts donors provided two different types of bridged-ring systems.