Ensemble effects on allylic oxidation within explicit solvation environments.

Area of Science:

• Computational Chemistry
• Catalysis Science
• Organic Chemistry

Background:

• Allylic oxidation of cyclohexene is a key transformation in organic synthesis.
• Copper complexes are effective catalysts for oxidation reactions.
• Understanding catalytic cycles is crucial for optimizing reaction efficiency.

Purpose of the Study:

• To elucidate the full catalytic cycle of cyclohexene allylic oxidation using a specific copper complex.
• To identify and differentiate reaction pathways involved in catalyst recovery.
• To provide a comprehensive understanding of radical reactions in catalysis.

Main Methods:

• Umbrella-sampling density functional theory molecular dynamics (DFT-MD) simulations were employed.
• Explicit solvent environment simulations were used to capture reactive species configurations.
• Energy span calculations were performed to compare reaction pathways.

Main Results:

• Two distinct catalytic pathways, an "open" cycle and a "closed" cycle, were identified.
• Both pathways involve reversible dehydrogenation and re-hydrogenation of a key -NH2 group.
• The "open" cycle exhibited a lower energy span (16.5 kcal mol-1) compared to the "closed" cycle (26.2 kcal mol-1).
• Simulations revealed the importance of ensemble sampling of solute and solvent configurations.

Conclusions:

• The study provides a detailed mechanistic insight into the allylic oxidation of cyclohexene.
• Ensemble sampling in DFT-MD offers a more comprehensive understanding than static calculations.
• The findings highlight the significance of radical reactions and catalyst recovery in the observed catalytic cycle.