# Molecular dynamics of bicyclo[2.2.0]hex-2-ene ring opening and its polar derivative: allowed vs. forbidden pathways

## TL;DR

The study investigates the ring-opening reactions of a specific hydrocarbon and its derivative, revealing how molecular dynamics and electronic effects influence reaction pathways.

## Contribution

The novel contribution is the discovery of dynamic behavior and disrotatory pathways enabled by charge separation in a substituted derivative.

## Key findings

- The hydrocarbon exhibits both conrotatory and disrotatory ring-opening pathways involving a diradical transition state.
- Non-statistical dynamic behavior with a short-lived intermediate is observed in the formally forbidden process.
- Charge separation in the derivative eliminates orbital symmetry restrictions, enabling a sterically favored disrotatory pathway.

## Abstract

We employed density functional theory, CCSD(T) and CASSCF computations, along with quasi-classical molecular dynamics simulations, to explore the ring opening of bicyclo[2.2.0]hex-2-ene and its 1-amino-4-cyano derivative. While the overall reaction is a formally forbidden 4-electron disrotatory electrocyclization, both conrotatory and disrotatory pathways operate for the hydrocarbon, the latter involving a HOMO–LUMO crossing and diradical transition state. Quasi-classical simulations reveal the presence of non-statistical dynamic behavior involving a short-lived intermediate in the formally forbidden process. For the donor/acceptor-substituted derivative, the charge separation induced by substitution eliminates orbital symmetry restrictions, enabling a sterically favored disrotatory pathway.

We employed density functional theory, CCSD(T) and CASSCF computations, along with quasi-classical molecular dynamics simulations, to explore the ring opening of bicyclo[2.2.0]hex-2-ene and its 1-amino-4-cyano derivative.