C-C Bond Formation Reaction Catalyzed by a Lithium Atom: Benzene-to-Biphenyl Coupling

Area of Science:

• Computational Chemistry
• Organic Synthesis
• Catalysis

Background:

• Transition-metal-catalyzed carbon-carbon (C-C) bond formation is crucial in chemistry but often expensive and complex.
• Existing methods rely on costly transition metals, prompting a search for alternatives.

Purpose of the Study:

• To propose and investigate a novel, transition-metal-free C-C coupling reaction catalyzed by lithium.
• To explore the mechanism of benzene (Bz) coupling into biphenyl using computational methods.

Main Methods:

• Utilized ab initio calculations to study the reaction pathway.
• Employed direct ab initio molecular dynamics (AIMD) to simulate the reaction under electron attachment.
• Calculated reaction barriers and intermediate structures.

Main Results:

• A stable complex of two benzene molecules with a Li- ion was identified (Bz(Li-)Bz).
• The C-C coupling reaction proceeds spontaneously with a calculated negative barrier height (-9.9 kcal/mol).
• Biphenyl formation was observed directly, even under electron attachment to Li(Bz)2, and for halogen-substituted benzenes.

Conclusions:

• Lithium-catalyzed C-C coupling offers a viable, transition-metal-free alternative for biphenyl synthesis.
• The reaction mechanism involves spontaneous C-C bond formation without a significant activation barrier.
• This approach is potentially applicable to substituted benzene derivatives.