The Mechanism of Rhodium-Catalyzed Allylic C-H Amination

Area of Science:

• Organometallic Chemistry
• Catalysis
• Organic Synthesis

Background:

• Cp*Rh complexes are effective catalysts for various organic transformations.
• Understanding the detailed mechanism of catalytic allylic C-H amination is crucial for developing new synthetic methodologies.

Purpose of the Study:

• To elucidate the mechanism of catalytic allylic C-H amination reactions promoted by Cp*Rh complexes.
• To identify key intermediates and reaction steps, including the role of oxidants and the nature of the catalytic species.

Main Methods:

• Reaction kinetics experiments
• Stoichiometric studies
• Density Functional Theory (DFT) calculations
• Quantum mechanical calculations
• Cyclic voltammetry
• Bulk electrolysis

Main Results:

• Allylic C-H activation to form a Cp*Rh(π-allyl) complex occurs under mild conditions.
• An oxidatively induced reductive elimination involving a Rh(IV) intermediate and an acetate ligand was proposed and supported by experimental and computational evidence.
• Evidence for the amination of an allylic acetate intermediate was presented.
• Cp*Rh(III)2+ acts as a Lewis acid catalyst to facilitate the final amination step.

Conclusions:

• The mechanism involves allylic C-H activation, oxidation, reductive elimination through a Rh(IV) intermediate, and subsequent Lewis acid-catalyzed amination.
• The study provides a comprehensive mechanistic understanding of Cp*Rh-catalyzed allylic C-H amination.
• This work contributes to the rational design of catalysts for C-H functionalization reactions.