Carbonylation reactions of alkynes and alkenes have attracted significant attention in organic synthesis. 1 Although metal- catalysed carbonylation reactions are well known, we have been interested in radical-mediated carbonylation reactions. Alkyl radicals generated by the addition of phenylthio radical to alkenes are known to be effectively trapped by molecular oxygen,* we envisioned that such radicals could also be trapped by carbon monoxide to give the ...