Reaction of unsaturated phosphonate monoesters with bromo- and iodo(bis-collidine) hexafluorophosphates

Reaction of unsaturated phosphonate monoesters with bromo- and iodo(bis-collidine) hexafluorophosphates are reported to lead to the formation of five- to seven-membered phostones by exo mode cyclizations. When the chains of the unsaturated phosphonate monoesters are substituted in α of the double bond by a dioxolane group endo mode cyclizations are observed. These cyclizations give rise to the formation of 1,2-oxaphosphepane-2-oxide and 1,2-oxaphosphocane-2-oxide.