Enantioselective iodocyclization and mercuriocyclization of γ-hydroxy- cis -alkenes

Asymmetric iodocyclization and mercuriocyclization of γ-hydroxy-cis-alkenes have been established. The iodocyclization has been attained with 1.2 equiv of iodine in the presence of the catalyst system prepared from 0.3 equiv of (R,R)-salen−Co(II) complex and 0.75 equiv of NCS to produce 2-substituted tetrahydrofurans with up to 90 % ee. The mercuriocyclization has been achieved using 1.2 equiv of Hg(II) complexed with 4-(2-naph- thyl)bisoxazoline (1:1 complex) in the presence of 5 equiv of K 2 CO 3 and 10 equiv of MeOH to procure 2-substituted tetrahydrofurans with up to 95 % ee.