A new, three-step, telescoped reaction sequence for the regioselective conversion of N-tosyl hydrazones and aziridines to 3,6-disubstituted and 3,5,6-trisubstituted 1,2,4-triazines is described. The process involves an efficient nucleophilic ring opening of the aziridine, giving access to a wide range of aminohydrazones, isolated with excellent yields. A “one-pot” procedure, combining the ring opening with a cyclization and an oxidation step, allows the preparation of diversified triazines in good yields.This work was supported by a postdoctoral fellowship from Pfizer (L.C.) and EPSRC Grant Nos. EP/K009494/1 and EP/M004120/1 (S.V.L.). We also thank Dr. Andrew D. Bond for conducting X-ray crystallographic analysis
