Highly selective cyclotrimerization of acetonitrile was achieved in the presence of a catalytic amount of alkali under mild conditions to produce 4-amino-2,6-dimethylpyrimidine in satisfactory yields. Among different base catalysts sodium hydride has the highest activity in this reaction. This catalytic system is also efficient for reactions of other nitriles having alpha-hydrogen. Linear dimers, linear- or cyclo-trimers can be obtained selectively. (C) 2003 Elsevier Science B.V. All rights reserved.