Aryl halide cross-coupling via formate-mediated transfer hydrogenation.

Area of Science:

• Organic Chemistry
• Catalysis
• Organometallic Chemistry

Background:

• Transfer hydrogenation is a key industrial process.
• Aryl halide reductive cross-coupling is underdeveloped due to hydrogenolysis.
• Palladium(I) species offer unique reactivity for catalytic transformations.

Purpose of the Study:

• To develop an efficient catalytic system for aryl halide reductive cross-coupling.
• To overcome the challenge of competing hydrogenolysis in cross-coupling reactions.
• To explore the utility of palladium(I) species in novel catalytic cycles.

Main Methods:

• Utilizing a palladium(I) precatalyst, [Pd(I)(P^tBu3)]2.
• Employing formate-mediated hydrogen transfer for reductive coupling.
• Investigating catalytic activity through experimental and computational studies.

Main Results:

• Achieved efficient reductive cross-coupling of activated aryl bromides with aryl iodides.
• Demonstrated orthogonality with Suzuki and Buchwald-Hartwig couplings.
• Showcased effectiveness for challenging 2-pyridyl systems due to chelated intermediates.
• Identified a unique catalytic cycle involving Pd(I) to dianionic Pd species conversion and transmetallation.

Conclusions:

• The developed catalytic system enables selective aryl halide reductive cross-coupling.
• The unique catalytic cycle involving Pd(I) species facilitates facile oxidative addition and selective reductive elimination.
• This method offers a valuable alternative for synthesizing biaryl compounds, especially those with challenging functional groups.