Heterogeneous Rhodium Single-Atom-Site Catalyst Enables Chemoselective Carbene N-H Bond Insertion

Area of Science:

• Organic Chemistry
• Catalysis
• Materials Science

Background:

• Transition-metal-catalyzed carbene insertion into N-H bonds is vital for C-N bond construction.
• Homogeneous catalysts face chemoselectivity challenges due to highly electrophilic metal carbene intermediates.
• Developing selective heterogeneous catalysts is crucial for efficient organic synthesis.

Purpose of the Study:

• To develop a highly selective heterogeneous catalyst for transition-metal-catalyzed carbene insertion reactions.
• To address the chemoselectivity limitations of existing homogeneous catalysts.
• To explore the potential of single-atom-site catalysis in organic synthesis.

Main Methods:

• Synthesis of a rhodium single-atom-site (Rh-SA) catalyst doped in a carbon support with N and P atoms.
• Testing the Rh-SA catalyst's performance in carbene insertion reactions with anilines, heteroaryl amines, and diazo esters.
• Utilizing density functional theory (DFT) calculations to elucidate the catalytic mechanism and selectivity.

Main Results:

• The Rh-SA catalyst demonstrated exceptional performance with low catalyst loading (0.15 mol %).
• Selective N-H insertion into aniline derivatives with multiple nucleophilic sites was achieved, unlike homogeneous catalysts producing side products.
• Consistent selectivity was observed across various diazo esters, indicating broad applicability.

Conclusions:

• Single-atom-site catalysis offers a powerful and selective approach for heterogeneous carbene insertion reactions.
• The Rh-SA catalyst provides superior chemoselectivity compared to homogeneous counterparts.
• The phosphorus atom in the catalyst support plays a key role in enhancing selectivity via accelerated proton transfer.