Figure 3 The potential energy surface for Pd(II)-catalyzed tranformation from 7 to products PR11and PR12 with L1 as the ligand. The free energies are given in kcal/mol.
From Figure 3, it can be clearly seen that TS8-9 andTS13-14 are the chemodivergence-determining transition states towards alkenyl chloride product (PR11) and trisubstituted olefin (PR12 ), respectively. The overall barrier for 13→TS8-9 associated with oxidative addition is lowered by 1.8 kcal/mol in comparison to 13→TS13-14 related to protonation process, which means that alkenyl chloride (PR11) is the major product. The calculated chemoselectivity is 9.4:1 in 298 K. The result is well consistent with the experimentally observed a 82:9 (9.1:1) ratio for the L1ligand-promoted Pd II -catalyzed C-H activation of arene with alkyne (entry 1 in Scheme 2). As seen from Figures 2 and 3, the rate-determining step of the whole catalytic cycle is CMD process via TS3-4 after the formation of active catalyst K . The reaction energy barrier for this step is 24.8 kcal/mol, which is comparable with the observed yield (81%) of major productPR11 under experimental conditions.