Visible Light Induced Rhodium(I)-Catalyzed C-H Borylation

Area of Science:

• Organometallic Chemistry
• Photocatalysis
• Organic Synthesis

Background:

• Aromatic C-H bond functionalization is crucial in organic synthesis.
• Developing efficient and sustainable catalytic methods, particularly using visible light, remains a key challenge.
• Rhodium complexes are versatile catalysts, but their application in visible-light photocatalysis for C-H borylation requires further exploration.

Purpose of the Study:

• To report an efficient visible light-induced rhodium(I)-catalyzed regioselective borylation of aromatic C-H bonds.
• To develop a stable and active photocatalytic system based on a single N-heterocyclic carbene-rhodium(I) complex.
• To elucidate the mechanism of the photocatalytic borylation reaction.

Main Methods:

• Visible light photocatalysis using blue LEDs.
• Employing a single N-heterocyclic carbene (NHC)-rhodium(I) complex.
• Investigating the reaction mechanism through experimental studies.

Main Results:

• Achieved efficient and regioselective borylation of aromatic C-H bonds under visible light irradiation.
• Demonstrated the stability and high photocatalytic activity of the NHC-Rh(I) complex.
• Identified a photooxidative ortho C-H bond addition pathway leading to a cyclometalated Rh(III)-hydride intermediate.

Conclusions:

• The developed NHC-Rh(I) photocatalytic system offers an efficient route for aromatic C-H borylation.
• The chelating NHC-carboxylate ligand is vital for catalyst stability and activity.
• The mechanistic insights provide a foundation for designing future photocatalytic systems.