Transition metal-catalyzed reactions have attracted much attention in synthetic organic chemistry due to their important role in the formation of C-heteroatom bonds. Ullmann coupling has risen in prominence in recent decades owing to its utilization in the synthesis of biaryl ethers found in a wide range of natural products together with biologically essential molecules, including antibiotics and major industrial polymers. In this article we provide the current understanding of the theoretical aspects of the underlying mechanism of the Ullmann-type O-arylation reaction.
