Mechanistic Insights into Scandium-Catalyzed Hydroaminoalkylation of Olefins with Amines: Origin of Regioselectivity and Charge-Based Prediction Model

DFT calculations
have been carried out on the Sc-catalyzed regioselective
hydroaminoalkylation of olefins with amines. It has been revealed
that the true active species is an amine-coordinated η2-azametallacyclic complex, and electronic factors play a crucial
role in achieving regioselectivity. The charge dispersion and charge
alternation account well for the stability of the olefin insertion
transition states and products. The charge distribution of 15 olefin
substrates used previously in the experimental studies correlates
well with the observed regioselectivity and could thus provide a potential
model for regioselectivity prediction. The reactivity of different
types of C–H bonds was also explored by modeling the reaction
of (CH2C6H4NMe2-o)2Sc+ with iPrN­(Me)­(Et). The suggested reactivity trend for the Sc-catalyzed
hydroaminoalkylation follows the order of primary C–H bond
> secondary C–H bond > tertiary C–H bond.