Direct Arylation of Benzene with Aryl Bromides using High-Temperature/High-Pressure Process Windows: Expanding the Scope of C-H Activation Chemistry

作者：Pieber Bartholomaus; Cantillo David; Kappe C Oliver^*

来源：Chemistry - A European Journal, 2012, 18(16): 5047-5055.

DOI：10.1002/chem.201103748

• biaryls
• cross-coupling
• transition-metal catalysis
• microwave chemistry
• novel process windows
• organocatalysis

A detailed investigation on the direct arylation of benzene with aryl bromides by using first-row transition metals under high-temperature/high-pressure (high-T/p) conditions is described. By employing a parallel reactor platform for rapid reaction screening and discovery at elevated temperatures, various metal/ligand/base combinations were evaluated for their ability to enable biaryl formation through C-H activation. The combination of cobalt(III) acetylacetonate and lithium bis(trimethylsilyl)amide was subjected to further process intensification at 200 degrees C (15 bar), allowing a significant reduction of the catalyst/base loading and a dramatic increase in catalytic efficiency (turnover frequency) by a factor of 1000 compared to traditional protocols. The high-throughput screening additionally identified novel nickel- and copper-based metal/ligand combinations that favored an amination pathway competing with C-H activation, with the addition of ligands, such as 1,10-phenanthroline, having a profound influence on the selectivity. In addition to metal-based catalysts, high-T/p process windows were also successfully applied to transition-metal-free systems, utilizing 1,10-phenanthroline as organocatalyst.

• 出版日期2012-4