First Partially Intramolecular Palladium‐Catalyzed [2+2+2] Cycloaddition of Benzyne: Application to the Synthesis of Benzo[b]fluorenones

The palladium(0)‐catalyzed reaction of benzyne with suitably functionalized benzodiynes to afford benzo[b]fluorenones is described. The outcome of the reaction is affected by the steric and electronic properties of the diynes and proved to be regioselective when an unsymmetrically substituted aryne is used. This work represents the first example of a partially intramolecular [2+2+2] cycloaddition involving arynes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)