Continuing their work on radical carbonylations, Ryu and coworkers designed a method for the formation of lactones (32)
from their conditions (Figure 6).22 When irradiated with light, this
radical/radical/reduction process begins with the abstraction of an
iodine atom from 30 to form radical 33. This primary radical then
adds to olefin 31 to form 34, which can add to an equivalent of
CO to form keto-radical 35. Reduction of this intermediate results
in the formation of organopalladium(II) complex 36. Addition of
the pendant hydroxyl group and reductive elimination regenerates
the catalyst and forms lactone 32 in a 77% yield.