A DFT Study on the Conversion of Aryl Iodides to Alkyl Iodides: Reductive Elimination of R-I from Alkylpalladium Iodide Complexes with Accessible -Hydrogens

DFT calculations have been performed on the palladium-catalyzed carboiodination reaction. The reaction involves oxidative addition, alkyne insertion, C-N bond cleavage, and reductive elimination. For the alkylpalladium iodide intermediate, LiOtBu stabilizes the intermediate in non-polar solvents, thus promoting reductive elimination and preventing -hydride elimination. The C-N bond cleavage process was explored and the computations show that PPh3 is not bound to the Pd center during this step. Experimentally, it was demonstrated that LiOtBu is not necessary for the oxidative addition, alkyne insertion, or C-N bond cleavage steps, lending support to the conclusions from the DFT calculations. The turnover-limiting steps were found to be C-N bond cleavage and reductive elimination, whereas oxidative addition, alkyne insertion, and formation of the indole ring provide the driving force for the reaction.