Enantioselective, desymmetrizing bromolactonization of alkynes.

Asymmetric bromolactonizations of alkynes are possible using a desymmetrization approach. The commercially available catalyst (DHQD)2PHAL promotes these cyclizations in combination with cheap NBS as a bromine source to give bromoenol lactones in high yield and with high enantioselectivity. The bromoenol lactone products, containing a tetrasubstituted alkene and a quaternary stereocenter, are valuable building blocks for synthetic chemistry.