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Published February 8, 2023 | public
Journal Article

Hidden intermediate activation: a concept to elucidate the reaction mechanism of the Schmittel cyclization of enyne-allenes

Abstract

The mechanistic paradigm in which the Schmittel cyclization transitions from one-step to stepwise has been investigated through the stabilization of a full hidden intermediate in the framework of the Diabatic Model of Intermediate Stabilization. Hidden intermediate activation was studied in silico employing quasi-classical trajectories and the Electron Localization Function. The stabilization of hidden intermediates achieved by substituting enyne–allenes with cyano and nitro groups generates the appearance of a partially hidden and an explicit intermediate, leading to one-step asynchronous biradical and stepwise biradical/zwitterionic mechanisms, respectively. The mechanistic feature associated with the activation level of the hidden intermediate arises from the Thornton effect and non-RRKM dynamics, where in the case of the CN-substituted system, despite having a single transition state, 54% of the effective trajectories remain in the intermediate zone after 540 fs, indicating that a mixture of mechanisms is observed.

Additional Information

The authors acknowledge FONDECYT Grant No. 1221803 and Anillo Grant ACT192175. C.B.M thanks Postdoctoral FONDECYT Grant N. 3200949 for the financial support. The high-performance computing system of PIDi partially supported this research – UTEM (SCC – PIDi – UTEM – CONICYT – FONDEQUIP EQM 180180). Powered@NLHPC: this research was partially supported by the supercomputing infrastructure of the NLHPC (ECM-02). Finally, R. A. M. would like to acknowledge the helpful discussions on this and related topics with Prof. Rudolph A. Marcus at Caltech.

Additional details

Created:
August 22, 2023
Modified:
October 23, 2023