DFT studies on the reaction mechanism of Ru(II)-catalyzed the C[sbnd]H activation of aromatic amide and alkylation of non-active olefins

Abstract

Density functional theory were performed to investigate the ruthenium-catalyzed CH activation of aromatic amides and alkylation of 1-hexene. Our findings indicate that the plausible catalytic cycles encompass CH activation, 1-hexene insertion, protonation, catalyst recovery, and the final product formation. Our calculations confirm that the [SbF6]− fragment remains positioned between ligand p-cymene and reactant aromatic amide(1a). Given that the reactant 1-hexene(2a) presents two potential reaction sites, a detailed discussion of the reaction branching point, resulting in two distinct products, is provided. The modified energy span model deduced that the turnover frequency (TOF) determining transition state (TDTS) and intermediate (TDI) correspond to the CC coupling transition states (TS5a or TS5b) and initial point, respectively. Considering the concentration effect of reactant 2a, the calculated apparent free-energy barriers for these two reaction pathways are 30.3 and 31.9 kcal mol−1. This difference offers a rational explanation for the observed experimental product ratio.