Ligand-free Stille cross-coupling reaction using Pd/CaCO3 as catalyst reservoir

Stille reactions between halobenzenes and other substituted (hetero)arenes and tributylphenyltin were carried out in ethanol–water solution using Pd/CaCO3 as catalyst in a ligand-free system. The catalyst could be recycled three times without any loss of activity. The ethanol–water solution, after removal of the catalyst and extraction of the product, was found to have catalytic activity, thus showing the presence of soluble Pd(0)/Pd(II) species that can be regarded as the true catalysts.