Colletto et al. developed a regioselective -arylation of benzo[b]thiophenes at room temperature with aryl iodides as coupling partners and sought to understand the mechanism of this reaction by performing natural abundance kinetic isotope effect measurements via single pulse NMR.
The observation of a primary C isotope effect at C3, an inverse H isotope effect, a secondary C isotope effect at C2, and the lack of an H isotope effect at C2 lead Colletto et al. to suggest a Heck-type reaction mechanism for the regioselective -arylation of benzo[b]thiophenes at room temperature with aryl iodides as coupling partners.
Frost et al. sought to understand the effects of Lewis acid additives on the mechanism of enantioselective palladium catalyzed C-N bond activation using natural abundance kinetic isotope effect measurements via single pulse NMR.
The primary C kinetic isotope effect observed in the absence of BPh suggests a reaction mechanism with rate limiting cis oxidation into the C–CN bond of the cyanoformamide. The addition of BPh causes a relative decrease in the observed C kinetic isotope effect which led Frost et al. to suggest a change in the rate limiting step from cis oxidation to coordination of palladium to the cyanoformamide.