Study of the Torquoselectivity of a Set of Unusual Ring-Opening Electrocyclic Reactions: Determination of the Electronic Bonding Structure Through the Methodologies of Natural Bond Orbital Analysis and Quantum Theory of Atoms in Molecules, and Analysis of the Electronic Reaction Mechanism Through Bond Reactivity Descriptors

In this work, we have studied the torquoselectivity of a set of unusual ring-opening electrocyclic reactions that have not been successfully rationalized using models based on orbital symmetry nor have they been explained by steric hindrance. Firstly, the corresponding transition states have been obtained, and it has been verified that the intrinsic reaction coordinates associated with these transition states are consistent with the reactants and products of the reactions studied. This has allowed us to theoretically calculate the reaction barriers (with their corresponding thermal corrections) and compare them with the corresponding experimental values. In a second step, we have analyzed the electronic bonding structure using the methodologies of Natural Bond Orbital Analysis and Quantum Theory of Atoms in Molecules, searching for interactions that may significantly stabilize the transition states. Finally, we have analyzed the reactivity using a recent model that has allowed us to calculate the corresponding bond reactivity descriptors.