Pyridazine derivatives have received much attention due to their reactions. Since, many pyridazine derivatives possess potential therapeutic effects, one can expect that replacement of a heterocyclic aromatic moiety in a bioactive molecule with the pyridazine nucleus would alter the physiochemical characteristics of that molecule significantly. Literature surveys showed that triazole, thiazole and thiophene derivatives, which are both commercially available drugs and agents under clinical investigations were the subject of a comprehensive review. On the other hand, Sulfonamides and sulfonylureas groups form the bioactive moiety of many compounds with therapeutically interest such as antibacterials, diuretics, antidiabetics and antibiotics. Also, mesoionic compounds have received much attention and have been extensively studied due to their unique structures, reaction behavior and pharmaceutical activities. All these properties aroused my interest in synthesizing new heterocyclic compounds including the triazolo, thiazolo and thieno pyridazine moieties and evaluating their biological activities as antibacterial and antidiabetic agents.