Mechanistic insight into the rhodium(III)-catalyzed ortho-selective coupling of diverse arenes with 4-acyl-1-sulfonyltriazoles: A computational study

摘要

A mechanistic study of the Cp*Rh(III)-catalyzed annulative coupling of benzimidates with 4-acyl-1-sulfonyltriazoles by C-H activation was performed using density functional M06 method. It was demonstrated that the active catalyst during the coupling process should be the cation [Cp*Rh(OAc)](+) rather than the neutral Cp*Rh(OAc)(2) and Zn(OAc)(2) as proposed previously by the experimenters. A novel energetically feasible reaction pathway has been revealed theoretically in details. The acetic acid-mediated cyclization process was confirmed to be the rate-limiting step with an overall barrier of 24.3 kcal/mol, excluding any importance of the C-H cleavage mechanism as supported by the kinetic isotope effect experiments. The major factors responsible for the preferred regioselectivity of N-pyrimidinylinoles with 4-acetyl-1-sulfonyltriazoles were discussed.