Lanthanum-Catalyzed Regioselective Synthesis of 1- or 4-Functionalized Dibenzofurans via Aryne Intermediates.

Regioselectively functionalized dibenzofurans are of significant value due to their prevalence in natural products, biologically active molecules, and organic materials. Here, we report a lanthanum-catalyzed synthesis of 1- or 4-functionalized dibenzofurans from halogenated 2-arylphenols or diaryl ethers. The reaction is initiated by deprotonation or halogen-metal exchange followed by C-H and C-F bond activation via aryne intermediates, leading to the formation of 1- or 4-lithiated dibenzofurans for electrophilic trapping reactions. The precise generation of aryne's triple bond at specific positions controls the product regioselectivity. This method features multifold bond cleavage and formation, a one-pot two-step protocol, and convenient product derivatization, thus expanding the scope of rare-earth catalysis and introducing new possibilities in organic synthesis.