Regioselective formation of a 2,3-oxaphosphabicyclo[2.2.2]octene 3-oxide in Baeyer-Villiger type oxidation; a dual pathway for its fragmentation

The O-insertion reaction of a 7-phosphanorbornene (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 inediated and the thermoinduced phosponylation accomplished on the bridged P-heterocycle (4a) were found to be sensitive toward steric factors, suggesting that beside the well-known elimination-addition reaction path laking place via metaphosphonate (11), a competitive novel addition-elimination route involving all intermediate with a pentacoordinated P-atom (12) is also present. This was confirmed by the kinetic consideration of our experimental data. (c) 2006 Wiley Periodicals, Inc.