REACTIONS OF TRIPHENYLBORANE WITH PHOTOEXCITED KETONES AND WITH DIAZODIARYLMETHANES

Article abstract of DOI:10.1016/0022-328X(85)80392-2

Aromatic ketones and diones when exposed to UV irradiation in the presence of triphenylborane give R₂<*>-OBPh₂ radicals through an S_H2 displacement of phenyl from BPh₃ by the excited triplet state of the carbonyl derivative.Very persistent radicals, characterized by g-factors higher than 2.0040, are obtained when boron is compelled to lie in the molecular plane owing to chelation by an electron-rich atom, such as oxygen (diones) or nitrogen.In some of these radicals, coupling of the unpaired electron with protons of the BPh₂ group was also observed.Diazodiarylmethanes react spontaneously with triphenylborane by a heterolytic pathway, which eventually leads to the formation of triphenylmethyl radical.