Towards heterogeneous organocatalysis: chiral iminium cations supported on porous materials for enantioselective alkene epoxidation
作者:Philip C. Bulman Page、Andrew Mace、Damien Arquier、Donald Bethell、Benjamin R. Buckley、David J. Willock、Graham J. Hutchings
DOI:10.1039/c3cy00352c
日期:——
Enantiomerically pure iminium cations have been supported on a microporous support (zeolite Y) and on a mesoporous support (Al-MCM-41). These materials are effective asymmetric catalysts for the epoxidation of a range of aryl alkenes, giving high conversions quickly and with enantioselectivities similar to or in some cases even higher than are achievable using the corresponding iminium tetraphenylborates under homogeneous conditions. The catalysts can be simply recycled by filtration and washing. The methodology is illustrated in the synthesis of two natural products, (−)-(3′S)-lomatin and (+)-(3′S,4′R)-trans-khellactone, showing the general efficacy of our approach.
对映体纯亚胺阳离子被支持在微孔支持物(沸石 Y)和介孔支持物(Al-MCM-41)上。这些材料是一系列芳基烯烃环氧化反应的有效不对称催化剂,可快速实现高转化率,其对映体选择性与在均相条件下使用相应的四苯基硼酸亚胺所实现的对映体选择性相似,在某些情况下甚至更高。催化剂只需过滤和洗涤即可循环使用。该方法通过合成两种天然产物--(-)-(3′S)-洛马汀和(+)-(3′S,4′R)-反式黄柏内酯进行了说明,显示了我们方法的普遍有效性。