DFT studies on the mechanisms of palladium-catalyzed intramolecular arylation of a silyl C(sp3)–H bond

Abstract

Detailed mechanisms of the intramolecular C(sp3)–C(sp2) bond formation via C(sp3)–H bond activation of a trimethylsilyl (TMS) substituent catalyzed by palladium(0) complexes have been investigated with the aid of density functional theory (DFT) calculations. The results reveal that the favorable catalytic cycle includes oxidative addition, ligand substitution, concerted metalation deprotonation (CMD) and reductive elimination steps. The CMD was found to be the rate-determining step with an overall free energy barrier of 26.4 kcal mol−1. For the analogous CMe3-substituted substrate, the C(sp3)–H bond activation of the CMe3 substituent was calculated to have a high free energy barrier of 29.9 kcal mol−1. Our calculation results show that during the deprotonation process of the TMS C(sp3)–H bond, the adjacent Si atom stabilizes the charge accumulated on the C(sp3)–H carbon and facilitates the C(sp3)–H bond activation due to the ability of Si to engage in Si–C hypervalent bonding.