Mechanistic Investigation of the Rhodium-Catalyzed Transfer Hydroarylation Reaction Involving Reversible C-C Bond...

Area of Science:

• Organic Chemistry
• Catalysis
• Organometallic Chemistry

Background:

• Carbon-carbon (C-C) bonds are fundamental but challenging to activate in organic synthesis.
• Existing catalytic C-C bond activation methods often require strained molecules or directing groups, limiting scope.
• Direct C-C bond reorganization offers a powerful strategy for molecular skeleton manipulation.

Purpose of the Study:

• To conduct a detailed mechanistic investigation of catalytic C-C bond cleavage in unstrained alcohols.
• To elucidate the mechanism of a Rh-catalyzed reversible ketone transfer hydroarylation reaction.
• To identify key intermediates, rate-determining steps, and catalyst behavior for reaction optimization.

Main Methods:

• Kinetic analysis to determine reaction rates and dependencies.
• In situ Nuclear Magnetic Resonance (NMR) spectroscopy for real-time reaction monitoring.
• Density Functional Theory (DFT) calculations to model reaction pathways and transition states.

Main Results:

• A symmetric catalytic cycle was proposed, featuring a reversible β-carbon elimination as a key step.
• Identification of the turnover-limiting step and the catalyst resting state under reaction conditions.
• The role of a sterically hindered N-heterocyclic carbene (NHC) ligand in the catalytic cycle was clarified.

Conclusions:

• The study provides a rare example of catalytic C-C bond cleavage in unstrained alcohols.
• Mechanistic insights led to the development of an improved catalytic system with higher activity.
• Two new air-stable precatalysts were discovered, enhancing the practical utility of the transformation.