HKUST‐1‐Catalyzed Homocoupling of Arylboronic Acids.

Symmetrical biaryl compounds are vital chemical feedstocks in the fine chemical industry. Homocoupling, which produces aryl‐aryl reagents, remains the predominant method for their synthesis. Previously, Yaghi et al. reported a patent demonstrating the high performance of HKUST‐1 in homocoupling reactions involving arylboronic acids with electron‐withdrawing substituents. However, reactions with electron‐donating substituents yielded lower results. In this study, we introduce optimized protocols for HKUST‐1 catalyzed homocoupling of arylboronic acids with electron‐donating substituents, achieving symmetrical biaryl products with yields up to 93 %. We also observed significant hydroxylation byproducts competing with homocoupling products when the reaction was exposed to air, especially for arylboronic acids with electron‐donating substituents. This heterogeneous HKUST‐1 catalyst demonstrated recyclability for up to three cycles without a significant decline in catalytic activity. [ABSTRACT FROM AUTHOR]