Cu-Catalyzed Reaction of 1,2-Dihalobenzenes with 1,3-Cyclohexanediones for the Synthesis of 3,4-Dihydrodibenzo[<i>b,d</i>]furan-1(2<i>H</i>)‑ones

The Cu­(I)-catalyzed reaction of 1-bromo-2-iodobenzenes and other 1,2-dihalobenzenes with 1,3-cyclohexanediones in DMF at 130 °C using Cs₂CO₃ as a base and pivalic acid as an additive selectively delivers 3,4-dihydrodibenzo­[<i>b</i>,<i>d</i>]­furan-1­(2<i>H</i>)-ones with yields ranging from 47 to 83%. The highly regioselective domino process is based on an intermolecular Ullmann-type <i>C</i>-arylation followed by an intramolecular Ullmann-type <i>O</i>-arylation. Substituted products are accessible by employing substituted 1-bromo-2-iodobenzenes and substituted 1,3-cyclohexanediones as substrates. Reaction with an acyclic 1,3-diketone yields the corresponding benzo­[<i>b</i>]­furan