Asymmetric amplification is a curious phenomenon that is believed to play a key role in the emergence of biological homochirality, and thus of life itself. In asymmetric catalysis, it is achieved via positive nonlinear effects, which allow high product enantiomeric excesses with a non-enantiopure catalyst. However, it has also been proposed that non-enantiopure catalysts may be even more enantioselective than their enantiopure counterparts, although such a case has never been experimentally observed so far. Here, we present an example of such a hyperpositive nonlinear effect in asymmetric catalysis. We found that addition of dialkylzinc reagents to benzaldehyde gave higher product enantiomeric excesses with only partially resolved chiral N-benzyl-ephedrine ligands. A mechanistic study was carried out and our results point towards a two-component catalysis, where mononuclear as well as aggregated catalysts are in equilibrium and in competition. These results introduce an unprecedented class of asymmetric amplification in enantioselective catalysis.

不对称扩增是一种奇怪的现象，据信在生物同手性的出现以及生命本身的出现中起着关键作用。在不对称催化中，它是通过正非线性效应来实现的，该效应可以通过非对映纯催化剂实现高产物对映体过量。但是，也有人提出非对映体纯的催化剂可能比对映体纯的对映体具有更高的对映选择性，尽管到目前为止这种情况从未在实验上观察到。在这里，我们介绍了在不对称催化中这种高正非线性效应的例子。我们发现在苯甲醛中添加二烷基锌试剂会产生较高的产物对映体过量，而手性N只能部分分解-苄基麻黄碱配体。进行了一项机理研究，我们的结果指向了两组分催化，其中单核以及聚集的催化剂处于平衡和竞争状态。这些结果在对映选择性催化中引入了前所未有的一类不对称扩增。