Cyclic alpha,beta-epoxyketones are converted to bi- or tricyclic beta-
hydroxyketones in the presence of n-Bu3Sn. radical. Addition of n-Bu3S
n. to the carbonyl group gives a ketyl radical that triggers the epoxi
de fragmentation which is then followed by a 1,5-hydrogen abstraction
and cyclization. Reversibility in the last two steps of the sequence i
s demonstrated.