Density functional studies on the Nazarov reaction involving cyclic systems

Area of Science:

• Organic Chemistry
• Computational Chemistry
• Reaction Mechanism

Background:

• The Nazarov reaction is a vital organic transformation for synthesizing cyclopentenones.
• Understanding the reaction mechanism, especially in cyclic systems, is crucial for synthetic control.
• Computational methods offer powerful tools for elucidating reaction pathways and energetics.

Purpose of the Study:

• To computationally investigate the energy profiles of the Nazarov reaction in cyclic systems.
• To explore the influence of substrate modifications and heteroatoms on reaction rates.
• To determine the factors controlling the stereochemical outcome of the electrocyclization step.

Main Methods:

• Density Functional Theory (DFT) calculations using the B3LYP/6-311G** level of theory.
• Estimation of solvent effects (dichloromethane) using the SM5.43R solvation model.
• Analysis of energy profiles for electrocyclization of substituted pentadienyl cations within cyclic frameworks.

Main Results:

• DFT calculations successfully defined the energy profiles for the Nazarov reaction in various cyclic systems.
• Substrate modifications and the presence of heteroatoms significantly impact reaction rates.
• The study elucidated the torquoselectivity, explaining the preference for 2,5-trans-disubstituted products in O-heterocycles.

Conclusions:

• Computational DFT results provide a rational explanation for experimental observations in cyclic Nazarov reactions.
• The findings can guide the interpretation and prediction of outcomes for Nazarov reactions in novel cyclic systems.
• This study enhances the understanding of stereochemical control in Nazarov cyclizations.