Sulfated tungstate catalyzed activation of nitriles: addition of amines to nitriles for synthesis of amidines

An efficient and mild method for the synthesis of amidines by direct nucleophilic addition of amines to nitriles using sulfated tungstate as heterogeneous catalyst is described. Highlight of the method is its applicability for the synthesis of amidines using a wide variety of amines including ammonia as ammonium acetate and nitriles. Catalyst is mildly acidic, stable, easy to prepare and separate from the reaction mass.