readily synthesized by electrophiliccarbocyclization of aryl propargylic alcohols in moderate to good yields under mild conditions. The resulting diiodide can be further exploited by subsequent oxidizing and coupling reactions. Both the iodine anion and cation generated from I2 are used effectively. The presence of a trace amount of water is essential for this electrophilic cyclization.
Palladium-Catalyzed Tandem Dimerization and Cyclization of Acetylenic Ketones: A Convenient Method for 3,3‘-Bifurans Using PdCl<sub>2</sub>(PPh<sub>3</sub>)<sub>2</sub>
Alkynones undergo tandem dimerization and cyclization in the presence of PdCl2(PPh3)2 and triethylamine in tetrahydrofuran at room temperature to give 3,3'-bifurans predominantly. Other palladiumcatalysts while under similar conditions, by rearrangement, lead to 2,5-disubstituted furans. This distinguished property of PdCl2(PPh3)2 has been attributed to the involvement of hydridopalladium halide.