Differential selectivity measurements and competitive reaction methods as effective means for mechanistic studies of complex catalytic reactions

Role of the base and endogenous anions in “ligand-free” catalytic systems for the Suzuki–Miyaura reaction

“…However, the results of investigation of the Suzuki-Miyaura reaction under conditions of two arylboronic acids competing with one another were published in 2014, and these results are consistent with the opinion that arylboronate anions participate in the transmetalation process [19]. Unfortunately, the mea sured parameter of the competing reactions was inte gral selectivity rather than differential selectivity, and this fact made data interpretation much more difficult [20] and does not allow the study by Lima et al [19] to be considered as a kinetic one. In addition, these authors disregarded the fact that the base exerts an effect on the rate of reductive palladium elimination [11,13,14], which is the final stage of the catalytic cycle of the Suzuki-Miyaura reaction.…”

“…In addition, these authors disregarded the fact that the base exerts an effect on the rate of reductive palladium elimination [11,13,14], which is the final stage of the catalytic cycle of the Suzuki-Miyaura reaction. It was demon strated [20] that the selectivity in the competition reaction of two substrates (two arylboronic acids) may also depend on the rate of the reaction steps involving the common reactant, whose role in this case is played by the base, which affects the rate of reductive palla dium elimination.…”

“…2), as in the case of the complexes with the base, indicates that these complexes possibly make a contribution to the trans metalation stage. This possibility causes additional difficulties in the interpretation of the results of exper iments involving competing arylboronic acids [19], because the competition in this case takes place not on one common catalyst but on several active sites that can differ in selectivity [20].…”

Is the Mechanistic Scheme of the Heck‐Type Coupling with Unsaturated Substrates needed to be revised?

“…Earlier, we have studied the differential selectivity of catalytic reactions by analysis of so‐called “phase trajectories” [17] . The latter represent interdependencies of the concentrations of the products that are used for the estimation of differential selectivity.…”

“…The key feature of the phase trajectories is their independence on the concentration of active species [17] . Any change of the shape of the phase trajectory with varying the reaction conditions can be resulted from a change of the nature of substances participating in the selectivity‐determining step only.…”