There are several methods available for the cyanation of aryl halides. However a common problem with many of the more traditional methods is that they are very toxic# One method to full fill these criteria has been around for a while (Weissman S A et al, J. Org. Chem.2005, 70, 1508-1510.) Ligand- free, Palladium- catalyzed cyanation of aryl halides.Potassium hexacyanoferrate(II) has used as cyanide source. This result increase the list of metal catalyzed reactions that can be performed without ligand.
The advantage of this method is obvious, in contrast to other cyanating agents potassium hexacyanoferrate(II) is less poisonous# and can be handle without special precaution, due to the slow release of cyanide ions a significantly improved the catalytic productivity compared to previously know procedures in achieved.
#( KCN is extremely toxic (LDL0(oral, human) =2.86mg Kg-1 and develop HCN on contract with acidic water. K4[Fe(CN)6] is non toxic and used in food industry for metal precipitation in wine. Also it has been used as anti agglutinating auxiliary for NaCl (table salt). It is soluble in water without decomposition. Schareina T et al, Chem Commun., 2004, 1388-1389.)