Novel cyclometallated iridium catalysts for asymmetric hydrogenation of N-methyl and N-phenyl imines

Abstract

In this work, three acetophenone N-phenyl imine derivatives functionalized in the para position have been prepared and cyclometallated to Ir-MaxPHOX catalyst. One of the additives has a hydrogen bond acceptor group, while the others have bulky substituents. The behavior of these compounds in asymmetric hydrogenation of acetophenone N-methyl and N-phenyl imine substrates has been studied. The additive containing a hydrogen bond acceptor provided better enantioselectivity than the others. This reinforces the hypothesis that a hydrogen bond interaction between the catalyst and the substrate would increase the selectivity. Additives with bulky substituents provided worse results, probably due to steric hindrance, decreasing the selectivity