Cationic gold catalyst poisoning and reactivation

Area of Science:

• Organometallic Chemistry
• Catalysis
• Synthetic Organic Chemistry

Background:

• Gold catalysts are highly effective in various organic transformations.
• Cationic gold catalysis is sensitive to impurities that can poison the active species.
• Reduced turnover number (TON) is a common issue in gold-catalyzed reactions due to deactivation.

Purpose of the Study:

• To investigate the impact of common impurities on cationic gold catalyst reactivity.
• To identify methods for reactivating poisoned gold catalysts.
• To enable efficient gold catalysis at low catalyst loadings.

Main Methods:

• Investigated the effect of halides and bases as impurities on gold catalyst performance.
• Evaluated the efficacy of acid activators, such as triflic acid (HOTf) and indium triflate (In(OTf)3), in restoring catalyst activity.
• Monitored reaction progress and catalyst turnover number (TON) under various conditions.

Main Results:

• High gold affinity impurities (halides, bases) significantly reduce the TON of cationic gold-catalyzed reactions.
• The addition of suitable acid activators effectively reactivates the gold catalyst.
• Reactivated catalysts facilitate smooth reaction progression even at low gold catalyst loadings.

Conclusions:

• Careful control of solvent and reagent purity is crucial for maintaining gold catalyst activity.
• Acid activators are a viable strategy to overcome catalyst deactivation by impurities.
• This approach allows for efficient and economical use of gold catalysts in organic synthesis.