Hamilton Gregory L, Kang Eun Joo, Mba Miriam, Toste F Dean
Department of Chemistry, University of California at Berkeley, Berkeley, CA 94720, USA.
Science. 2007 Jul 27;317(5837):496-9. doi: 10.1126/science.1145229.
Traditionally, transition metal-catalyzed enantioselective transformations rely on chiral ligands tightly bound to the metal to induce asymmetric product distributions. Here we report high enantioselectivities conferred by a chiral counterion in a metal-catalyzed reaction. Two different transformations catalyzed by cationic gold(I) complexes generated products in 90 to 99% enantiomeric excess with the use of chiral binaphthol-derived phosphate anions. Furthermore, we show that the chiral counterion can be combined additively with chiral ligands to enable an asymmetric transformation that cannot be achieved by either method alone. This concept of relaying chiral information via an ion pair should be applicable to a vast number of metal-mediated processes.
传统上，过渡金属催化的对映选择性转化依赖于与金属紧密结合的手性配体来诱导不对称产物分布。在此，我们报道了在金属催化反应中手性抗衡离子赋予的高对映选择性。使用手性联萘酚衍生的磷酸根阴离子，阳离子金（I）配合物催化的两种不同转化反应生成了对映体过量90%至99%的产物。此外，我们表明手性抗衡离子可以与手性配体加成组合，以实现单独使用任何一种方法都无法实现的不对称转化。通过离子对传递手性信息的这一概念应该适用于大量的金属介导过程。
