The First Preparation of β-Lactones by Radical Cyclization

β-Lactones have, for the first time, been prepared by 4-exo-trig radical cyclization. Thus, α-ethenoyloxy radicals react in the presence of tributylstannane in a photothermal process to give β-lactones. Highest yields were obtained when groups capable of stabilizing a carbon-centered radical were present at the 3-position of the alkenoate acceptor