Synthesis of enol lactones via Cu(I)-catalyzed intramolecular O-vinylation of carboxylic acids.

With the catalysis of CuI/trans-N,N'-dimethylcyclohexane-1,2-diamine, a number of carboxylic acids underwent efficient intramolecular O-vinylation with vinyl bromides leading to the synthesis of the corresponding five- and six-membered enol lactones. The same catalytic system also led to the efficient cycloisomerization of alkynoic acids.