Two‐Stage, Sequential Aryne Carboiodanation Enabled by Mesomeric Priming

Carboiodanation of arynes with organo‐benziodoxoles (BXs) furnishes aryl‐BXs (ArBXs) bearing ortho ‐alkynyl, alkenyl, or aryl groups, which serve as versatile aromatic building blocks for downstream π‐extension through the aryl–iodine(III) bond. Although synthetically valuable, these primary carboiodanation products rarely participate in a second aryne addition due to insufficient nucleophilicity. Here we show that judicious pairing of organo‐BXs and arynes enables electronic activation of the initial ArBX product, rendering it competent for a second carboiodanation to afford biaryl‐BX derivatives. This unique reactivity arises from a BX‐specific arenium/iodate four‐membered cyclic intermediate, in which the positive charge is efficiently delocalized by mesomeric effects provided by substituents transferred from β‐alkoxyvinyl‐BXs (VBXs) and ethynyl‐BXs (EBXs), as well as the electron‐rich aryl framework formed upon initial aryne incorporation. The resulting biaryl‐BX scaffolds provide concise access to densely functionalized oligoarylenes and polycyclic aromatic frameworks.