ORGANIC LETTERS, vol.18, no.1, pp.84-87, 2016 (SCI-Expanded)
The thermal cyclization of enyne-carbodiimides substituted at both the alkyne and carbodiimide terminus showed two curved Hammett correlations (log k/k(0) against sigma(P)) that were fully reproduced by DFT (density functional theory) computational results. The latter suggest a concerted mechanism, but the transition state (TS) analysis failed to reveal any mechanistic insight about the reason for a curved Hammett correlation. Instead a preTS inspection, i.e., examination of the electronic and steric details on route between reactant and TS, furnished a detailed picture of the mechanism.