A nonlinear effect in asymmetric catalysis is a phenomenon in which the enantiopurity of the catalyst (or chiral auxiliary) is not proportional to the enantiopurity of the product obtained.
[1] In 1994, H. B. Kagan and collaborators proposed more elaborate models that more closely resembled the experimental results observed at the time.
Using these models, the authors were able to make theoretical predictions about situations that had not been encountered experimentally.
[2] The authors proposed the term “hyperpositive nonlinear effect” to characterize this situation.
This statement may seem somewhat implausible at first glance, but the possibility was observed experimentally 26 years later: the first experimental example of a hyperpositive nonlinear effect was described in 2020 by S. Bellemin-Laponnaz and colleagues,[3] but the mechanism of this phenomenon turned out to be different from that originally proposed.