Catalytic Enantioselective Iodocyclization of γ-Hydroxy-cis-alkenes

Enantioselective iodocyclization of γ-hydroxy-cis-alkenes has been achieved using I2 in the presence of an unprecedented catalyst system generated from (R,R)-t-Bu-salen−Co(II) complex and NCS to produce 2-monosubstituted tetrahydrofurans up to 90% ee. While NCS turned out to be the essential additive, neither (R,R)-salen−Co(II) nor (R,R)-salen−Co(III) by itself is likely to be the active species responsible for the asymmetric intramolecular iodoetherification.