Free radicals from cyclic enones: an electron paramagnetic resonance investigation. Part II. Radical additions

The addition of silyl and germyl radicals to a series of substituted cyclopentenones and cyclohexenones has been investigated using EPR spectroscopy. At low temperatures the 3-position is the preferred site for addition unless it is substituted or sterically hindered in which case addition occurs at the carbonyl oxygen. The latter process is also favoured at higher temperatures but no evidence has been obtained for either addition at the 2-position or for an intramolecular migration following initial attack at the 3- or 2-position.