Hydrazine Derivatives and O-Benzoylbenzoic Acid as a Source of Phthalazines with their Antimicrobial Activities

Starting from 2-benzoylbenzoic acid (1) and prototype hydrazine itself or some of its simple congeners produce phthalazin-1(2H)-one derivatives 2a–d. Reactions of 2 with P₂S₅ or POCl₃ gave their thione derivatives 3a–c or the chloro derivative 4 respectively. Further reactions of phthalazines 3 and 4 with hydrazine derivatives afforded their hydrazinyl derivatives 5a–d. Compounds 5a and 5d were used as a precursor to triazolo 6 and pyrazolyl phthalazines 7. The antimicrobial activities of some of the prepared phthalazines were tested.