Studies in the field of pyridazine compounds. Part 21. Structural studies on 6-H-pyrimido[1,2-b]-1,2,4-triazolopyridazines.

The structure of 7,8-dihydro-6H-pyrimido [1,2-b]-1,2,4-triazolo [3,4-f] pyridazine (2a) was confirmed by 1H and 13C NMR spectroscopy and by preparation of the isomeric [5,1-f] pyridazine 3. Some derivatives of 6H-pyrimido [1,2-b]-1,2,4,-triazolo [3,4-f]pyridazine were prepared. Compounds 2a, 2b and 9a showed a positive inotropic effect.