Palladium-catalyzed tandem dimerization and cyclization of acetylenic ketones: a convenient method for 3,3'-bifurans using PdCl2(PPh3)2

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 palladium catalysts 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. This method provides a simpler route to a variety of furans and a regioselective synthesis of polysubstituted 3,3'-bifurans using easily accessible acetylenic ketones.