Long-range C-H bond activation by Rh(III)-carboxylates

Area of Science:

• Organometallic Chemistry
• Catalysis
• Organic Synthesis

Background:

• Traditional C-H bond activation relies on concerted metalation-deprotonation (CMD), requiring precoordination and an internal base.
• Activating remote C-H bonds presents a significant challenge in synthetic chemistry.

Purpose of the Study:

• To report a novel "through-arene" C-H bond activation mechanism.
• To demonstrate the activation of an uncoordinated benzylic C-H bond six bonds away from a Rh(III) center.

Main Methods:

• Experimental investigations.
• Density Functional Theory (DFT) studies.
• Spectroscopic observation of a key intermediate.

Main Results:

• Successful activation of a remote, uncoordinated benzylic C-H bond.
• Elucidation of a mechanism proceeding through a dearomatized xylene intermediate.
• Observation of the dearomatized xylene intermediate using a pyridine base as a thermodynamic trap.

Conclusions:

• The study introduces a new paradigm for C-H bond activation, expanding the scope of remote functionalization.
• The findings provide valuable mechanistic insights into Rh(III)-catalyzed reactions and the formation of dearomatized intermediates.