Mechanistic Study on CpRh(III)-Catalyzed [3 + 2] Annulation of Aniline Derivatives with Vinylsilanes: A DFT Study.

The rhodium(III)-catalyzed reaction of aniline derivatives that contain a pyrimidine-directing group with vinylsilanes results in the formation of C3-substituted indoline derivatives. The reaction path and formation of the indoline product with density functional theory calculations were analyzed. This study reveals that the whole catalysis can be characterized in the following stages: (I) C-H activation via concerted metalation deprotonation, (II) 2,1-vinylsilane insertion, (III) deprotonation of the NH amide proton, (IV) the oxidation of Ag, and (V) reductive elimination. These steps are kinetically and thermodynamically feasible for experimental realization under mild conditions, and the insertion step with a barrier of 22.0 kcal/mol should not only be the critical step of regioselectivity but also the rate-determining step during the whole catalysis. Computations reveal that the Ag oxidation can accelerate the reductive elimination step after the formation of natural intermediate, thus highlighting the role of Ag as a catalytic promoter for the oxidatively induced reactivity of the Rh catalyst in C3-substituted indoline synthesis.