Theoretical insights into the mechanism of rhodium‐catalyzed, P^III‐directed regioselective CH arylation of indole with anhydride

Abstract

Density functional theory calculations were performed to study the reaction mechanism of Rh(I)‐catalyzed, P(III)‐directed regioselective CH arylation of indole with anhydride through decarbonylative cross‐coupling. This mechanism involves four major steps: CH activation, oxidative addition, decarbonylation, and reductive elimination. Through this theoretic study, we find that the CH bond activation was accomplished by the hydrogen carbonate (−HCO3)‐assisted concerted metalation‐deprotonation (CMD) process, not through the oxidative addition of Rh(I)‐catalyst. Meanwhile, our calculation results indicate that the regioselectivity of CH bond arylation of indole with anhydride can be attributed to the relative stability of the CMD transition states in the CH bond activation process. Moreover, in the CH activation step, the base (−HCO3) is not coordinated with the Rh center.

Solvent‐dependent mechanistic aspects for the redox reaction of paraquat in basic solution

“…The ΔG data represent the driving power of reactions, giving significant information for both thermal equilibrium constants (K) and rate constants (k) via: where Δ G r and Δ G ≠ denote the reaction Gibbs energy and activation free energy, respectively. It is worthwhile noting that the M06‐2X predicted Gibbs free energy profiles and thermodynamics have been successfully used to investigate mechanisms of many prototypical organic reactions, for example, the basic anion (HCO 3 − ) assisted C‐H activation, [ 35 ] effect of solvent polarity on the reaction energetics and selectivity of alkyne hydrochalcogenation, [ 36 ] organocatalytic asymmetric Povarov reactions of anilines and aldehydes, [ 37 ] regioselectivity for 1,3‐dipolar cycloadditions of diazomethane, [ 38 ] and even for the PQ‐containing charge transfer complexes. [ 39 ] Reasonable agreement between computation and experiment validates the computational protocols and demonstrates the significance of the theoretical results.…”