Two related routes for the synthesis of pemirolast potassium have been reported: 1) The condensation of 2-amino-3-methylpyridine (I) with ethoxymethylenemalonodinitrile (II) gives the monocyclic intermediate (III), which is in tautomeric equilibrium with the pyridopyrimidine derivative (IV). The reaction of (IV) with aluminum azide (AlCl3.NaN3) in refluxing THF yields 4-imino-9-methyl-3-(1H-tetrazol-5-yl)-4H-pyrido[1,2-a]pyrimidine (V). Finally, this compound is first hydrolyzed with 1N HCl and then treated with KOH. 2) Compound (IV) can be converted to the final product by a one-pot reaction: (VI) is treated first with NaN3 in refluxing acetic acid, then hydrolyzed with HCl and finally treated with KOH.