A Sequential Pd/Norbornene-Catalyzed Process Generates <i>o-</i>Biaryl Carbaldehydes or Ketones via a Redox Reaction or 6<i>H</i>‑Dibenzopyrans by C–O Ring Closure

<i>o</i>-Biaryl carbaldeydes and ketones are obtained through the one-pot reaction of <i>o</i>-aryl iodides with <i>o</i>-bromobenzyl alcohols under the catalytic action of Pd and norbornene, in the presence of a base. The same reaction can also give dibenzopyrans by Pd and norbornene catalysis with a different termination, leading to C–O ring closure. In both cases the process first leads to a five-membered palladacycle, which controls C–C coupling, then to a seven-membered oxapalladacycle, which gives aldehydes and ketones or dibenzopyrans