Iridium-Catalyzed Synthesis of Diaryl Ethers by Means of Chemoselective C-F Bond Activation and the Formation of B-F Bonds

Transition-metal-catalyzed C-F activation, in comparison with C-H activation, is more difficult to achieve and therefore less fully understood, mainly because carbon-fluorine bonds are the strongest known single bonds to carbon and have been very difficult to cleave. Transition-metal complexes are often more effective at cleaving stronger bonds, such as C(sp(2))-X versus C(sp(3))-X. Here, the iridium-catalyzed C-F activation of fluorarenes was achieved through the use of bis(pinacolato) diboron with the formation of the B-F bond and self-coupling. This strategy provides a convenient method with which to convert fluoride aromatic compounds into symmetrical diaryl ether compounds. Moreover, the chemoselective products of the C-F bond cleavage were obtained at high yields with the C-Br and C-Cl bonds remaining.