Unraveling unusual torquoselectivity in ring-opening electrocyclic reactions: a DFT perspective

Torquoselectivity in the electrocyclic ring-opening of perfluoro-3,4-dimethylcyclobutene is investigated through electron density-based approaches, including DFT, QTAIM, and stress tensor analysis. The study examines electronic redistribution and bonding patterns along the reaction pathway to elucidate and predict atypical stereochemical outcomes, such as the formation of the Z,Z isomer, with the aim of enhancing stereocontrol beyond the scope of traditional orbital-based models. A previously developed model based on Sanderson's electronegativity equalization principle is employed to compute the local reactivity indices. To identify the local contributions most relevant to the global properties, multiple regression analysis is applied. This approach allowed us to establish meaningful correlations between global and local descriptors, offering a deeper insight into the reactivity patterns observed in the studied reactions. Alongside, information-theoretic descriptors are employed to uncover the electronic structure basis of reaction pathway selectivity and molecular stability.