Synthesis and biological activity evaluation of differently substituted 1,4‐dioxo‐3,4‐dihydrophthalazine‐2(1H)‐carboxamides and ‐carbothioamides

Differently substituted phthalic anhydrides can react either with semicarbazide or thiosemicarbazide to give respectively 1,4‐dioxo‐3,4‐dihydrophthalazine‐2(1H)‐carboxamides or 1,4‐dioxo‐3,4‐dihydrophthal‐azine‐2(1H)‐carbothioamides under mild conditions and generally with good yields. These compounds have been tested in order to evaluate their anti‐microbial activity. Furthermore a new synthetic pathway to phtha‐lazino2,3‐b]phthalazine‐5,7,12,14‐tetraone has been devised.