Prediction on the origin of selectivities of NHC-catalyzed asymmetric dearomatization (CADA) reactions

Abstract

Prediction of the regioselectivities (i.e., the active sites) of dearomatization reactions has been and continues to be one of the most challenging issues in the modern synthesis field. In this work, we provide a valuable case for predicting the origin of the chemoselectivity for organocatalyst-catalyzed asymmetric dearomatization (CADA) reactions. Herein, the possible mechanisms and the origin of selectivities of NHC-catalyzed asymmetric dearomatization reaction of isoquinoline have been systematically investigated using density functional theory (DFT) for the first time. Computational results show that the intermolecular Mannich-type transformation was both the stereoselectivity- and chemoselectivity-determining step. The NCI analysis reveals that C–H⋯Br and π⋯π interactions contribute significantly to the control of the stereoselectivity. Furthermore, the origin of regioselectivities on NHC-catalyzed asymmetric dearomatization reactions of other aromatic rings has been accurately predicted by performing the local reactivity index analysis. This work would provide valuable clues for predicting the origin of the selectivities and designing more effective organocatalysts for these kinds of reactions with high and special selectivities.