Computational insights into the coupling mechanism of benzoic acid,phenoxy acetylene and dihydroisoquinoline catalyzed by silver ion as polarizer and stabilizer

The coupling mechanism of benzoic acid, phenoxy acetylene and dihydroisoquinoline in 1,4-dioxane was investigated in detail using the M06-L and M06-2X functionals. The barriers for the energetically more favorable pathway are 179.9, 85.4 and 82.7 kJ/mol. Ag⁺ activates and polarizes the C ≡ C triple bond of phenoxy acetylene, and stabilizes the intermediate of α-acyloxy enol ester. NCI analyses demonstrate that the π-π stacking does not facilitate the coupling of benzoic acid and phenoxy acetylene. Due to the fact that α-acyloxy enol ester is naturally highly polarized, the subsequent addition of α-acyloxy enol ester and dihydroisoquinoline can occur without the aid of Ag⁺. The atomic polar tensor (APT) charge and fuzzy bond order (FBO) analysis reveal the variation of the two C-N bonds.