Cul-Mediated Sequential Iodination/Cycloetherification of o-Arylphenols: Synthesis of 2-or 4-Iododibenzofurans and Mechanistic Studies

An efficient synthesis of 2- or 4-iododibenzofurans through Cul-mediated sequential iodination/cycloetherification of two aromatic C-H bonds in o-arylphenols has been developed. Both the preexisting electron-withdrawing groups (NO2, CN, and CHO) and the newly introduced iodide are readily modified for a focused dibenzofuran library synthesis. Mechanistic studies and DFT calculations suggest that a Cu(III)-mediated rate-limiting C-H activation step is involved in cycloetherification.