CuI-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 CuI-mediated sequential iodination/cycloetherification of two aromatic C-H bonds in o-arylphenols has been developed. Both the preexisting electron-withdrawing groups (NO(2), 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.