Evidence for the involvement of pentacoordinate P-intermediates during the UV light-mediated fragmentation of a 2-phosphabicyclo[2.2.2]octene 2-oxide in the presence of O-nucleophiles

Isotope-exchange experiments with H218O proved at least the partial involvement of a P(V)-species (8) as an intermediate in the UV light-promoted fragmentation of phosphabicyclooctene (1). Selection between the alcohols of equimolar mixtures during the photochemical fragmentation of 1 also suggests a mechanism where an adduct (4) is formed in the rate-determining step affording the phosphorylated product (5) after decomposition. We were able to prove that the transient adduct (4) is formed in a reversible manner.