Pd/Cu Co‐Catalyzed <i>ortho</i>‐Arylation of Aryl Iodides <i>via</i> Radical Intermediates with Aryl Diazonium Salts

Abstract A Cu/Pd co‐catalyzed Catellani‐type ortho arylation reaction of iodoarenes with aryl diazonium salts has been developed. Aryl radicals that derived from aryl diazonium salts were regioselectively installed at ortho position of iodoarenes via palladium catalyzed C−H activation. Mechanistic studies showed that, in contrast to classical Pd 0 −Pd II −Pd IV −Pd II −Pd 0 catalytic cycle, this radical cascades performed via a Pd 0 −Pd II −Pd III −Pd I −Pd 0 cycle.