The O-insertion reaction of a 7-phos- phanorbornene (3) unsubstituted on the double- bond gave the corresponding 2,3-oxaphosphabicyclo- [2.2.2]octene oxide (4a) in a regioselective manner that was useful in the fragmentation-related phosphonylation of alcohols. Both the UV-light mediated and the thermoinduced phosponylation accomplished on the bridged P-heterocycle (4a) were found to be sensitive toward