Catalytic Enantioselective Iodocyclization of γ-Hydroxy-<i>cis</i>-alkenes
作者:Sung Ho Kang、Sung Bae Lee、Chul Min Park
DOI:10.1021/ja0369921
日期:2003.12.1
Enantioselective iodocyclization of gamma-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.
Asymmetric Iodocyclization Catalyzed by Salen–CrIIICl: Its Synthetic Application to Swainsonine
作者:Hyo Young Kwon、Chul Min Park、Sung Bae Lee、Joo-Hack Youn、Sung Ho Kang
DOI:10.1002/chem.200701199
日期:2008.1.18
The previously developed enantioselective iodocyclization of gamma-hydroxy-cis-alkenes required 30 mol% of (R,R)-salen-Co(II) complex as chiral catalyst and 0.75 equivalent of N-chlorosuccinimide (NCS) as activator to produce 2-substituted tetrahydrofurans with 61 to 90% ee. Due to the considerable loading amount of the Co(II) complex, another more effective catalyst was pursued by screening (R,R)-salen-transition