Oxidative Addition, Transmetalation, and Reductive Elimination at a 2,2'-Bipyridyl-Ligated Gold Center

Area of Science:

• Organometallic Chemistry
• Catalysis
• Synthetic Organic Chemistry

Background:

• Palladium-catalyzed cross-coupling reactions are standard for biaryl synthesis.
• Developing alternative catalytic systems, especially using earth-abundant metals, is crucial.
• Gold catalysis offers unique reactivity profiles for C-C bond formation.

Purpose of the Study:

• To develop a novel monometallic gold complex for biaryl synthesis.
• To demonstrate all catalytic steps characteristic of palladium-catalyzed biaryl synthesis using gold.
• To investigate the mechanism of key steps, particularly oxidative addition.

Main Methods:

• Synthesis of three-coordinate bipyridyl gold complexes.
• Catalytic oxidative addition of aryl iodides to the gold center.
• Aryl-zinc transmetalation and C-C reductive elimination.
• Product characterization using spectroscopic methods.
• Computational studies to elucidate reaction mechanisms.

Main Results:

• Readily synthesized gold-bipyridyl ethylene complexes.
• Demonstrated sequential oxidative addition, transmetalation, and reductive elimination from a single gold complex.
• Identified that electron-rich aryl iodides react faster in the oxidative addition step.
• Computational analysis provided insights into the reversibility and substrate selectivity of oxidative addition.

Conclusions:

• A novel gold-catalyzed pathway for biaryl synthesis has been established, mimicking palladium catalysis.
• This gold-based system operates efficiently without the need for directing groups.
• The study provides mechanistic understanding of gold-catalyzed C-C bond formation, paving the way for further gold catalyst development.