Selim Khalid, Soeta Takahiro, Yamada Ken-ichi, Tomioka Kiyoshi
Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto, 606-8501, Japan.
Chem Asian J. 2008 Feb 1;3(2):342-50. doi: 10.1002/asia.200700302.
The asymmetric conjugate addition of dialkylzinc reagents to racemic 6-substituted cyclohexenones under the catalysis of chiral amidophosphane-copper(I) complexes gave a mixture of nearly equal amounts of the corresponding trans- and cis-disubstituted cyclohexanones with extremely high catalyst-controlled enantioselectivity. Epimerization with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) led to the conversion of these mixtures into the thermodynamically more stable trans-2,5-disubstituted cyclohexanone as the major product with up to 96% ee in up to 96% yield. The regio- and stereoselective alkylation of the disubstituted cyclohexanone products via the thermodynamically favored enolate gave 2,2,5-trisubstituted cyclohexanones with a quaternary asymmetric carbon atom in good yield.
在手性氨基膦 - 铜（I）配合物催化下，二烷基锌试剂与外消旋6 - 取代环己烯酮进行不对称共轭加成反应，得到了几乎等量的相应反式和顺式二取代环己酮的混合物，且具有极高的催化剂控制对映选择性。用1,8 - 二氮杂双环[5.4.0]十一碳 - 7 - 烯（DBU）进行差向异构化反应，可将这些混合物转化为热力学上更稳定的反式 - 2,5 - 二取代环己酮，其作为主要产物，产率高达96%，对映体过量值（ee）高达96%。通过热力学上有利的烯醇盐对二取代环己酮产物进行区域和立体选择性烷基化反应，可高产率地得到具有季碳不对称碳原子的2,2,5 - 三取代环己酮。
