The synthesis and X-ray crystal structure of a new class of fused heterocycle with 8,9-dihydro-pyridazino[1,2,4]triazine type 2 is reported. The synthesis is facile and efficient and, the structure of compounds was proven by elemental and spectral analysis, the X-ray spectra including (for 2b). The compound crystallizes in the space group P21/N (monoclinic) with a = 9.0077(2) �, b = 10.20019(18) �, c = 14.0099(3) �, a= 90�, b = 89.768(2)�, g= 90�, V= 1287.22(5) and Z = 4. Accurate molecular

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... meters for the heterocyclic system were obtained from intensity data collected at 200(14) K. The molecule 8,9-dihydro-pyridazino[1,2,4]triazine type 2 is a noncoplanar bicyclic fused system, with an envelope shape onto the triazine moiety, the C12 carbon being out of plane. The methyl group from the C12 carbon it is almost perpendicular on the triazine plane. We also notice a rather powerful hydrogen bond between hydrogen atom from N1 and the oxygen from the C11=O1 carbonyl group.