Switchable hydrogenation with a betaine-derived bifunctional Ir-NHC catalyst

Area of Science:

• Organometallic Chemistry
• Catalysis
• Organic Synthesis

Background:

• Quinoxaline derivatives are important in medicinal chemistry.
• Efficient and controllable hydrogenation methods are crucial for synthesizing these compounds.
• Developing catalysts with tunable activity is an ongoing challenge.

Purpose of the Study:

• To develop a novel bifunctional iridium catalyst for switchable hydrogenation of quinoxalines.
• To elucidate the mechanism of metal-ligand cooperative catalysis.
• To demonstrate the ability to control the catalytic activity using external stimuli (acid/base).

Main Methods:

• Synthesis of a novel iridium complex featuring a 'uracil-abnormal NHC' hybrid ligand.
• Catalytic hydrogenation reactions of quinoxalines using the developed iridium catalyst.
• Mechanistic studies involving control experiments to probe the reaction pathway.

Main Results:

• The bifunctional iridium catalyst successfully mediated the hydrogenation of quinoxalines.
• Control studies indicated a metal-ligand bifunctional mechanism involving heterolytic H2 activation.
• Catalysis could be reversibly switched on and off by adjusting the reaction conditions with acid or base.

Conclusions:

• A novel 'uracil-abnormal NHC' iridium catalyst enables switchable hydrogenation of quinoxalines.
• The catalytic process operates via a metal-ligand cooperative mechanism.
• External acid/base stimuli provide effective control over the catalytic activity, offering a new strategy for reaction management.