Novel metal-free Lewis acid catalysis by phosphonium salts through hypervalent interaction

Article abstract of DOI:10.1016/j.tet.2005.09.075

Phosphonium salts as a novel metal-free Lewis acid catalyst can be considered as organocatalysts. The introduction of a five-membered dioxaphosphacycle to the phosphonium salt is critical to its function as a Lewis acid catalyst for the Diels-Alder reacti