In this paper we report a feasible study concerning synthesis, structure and biological activity of some new pyridazine derivatives. Syntheses have been done both under classical conditions and microwave [in liquid phase and interphasic transfer catalysis (PTC)]. The MW induced a remarkable acceleration for the [3+2] dipolar cycloaddition reaction of pyridazinium ylides to activated alkenes and alkynes, the yields were increased in some cases, and the amount of used solvents decrees in liquid phase (while PTC do not use solvents). Consequently, these types of reactions could be considered environmentally friendly. The in vitro antibacterial and antifungal activities of the newly obtained diazine compounds were tested, some of the compounds have proved to have a remarkable activity against Gram positive germs, the results on Sarcinia luteea being spectacular.