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.