Aroylation of m-xylene by phthalic anhydride under Friedel craft's reaction conditions to afford the corresponding o-aroylbenzoic acid derivative (2), which followed by cyclization reaction with hydroxylamine hydrochloride to produce the correlating benzoxazinone derivative (3), which was utilized as a precursor for the formation of some novel phthalazinone derivatives (4˗6). This transformation was achieved by interactions with thiosemicarbazide, thiocarbohydrazide, and hydrazine monohydrate and/or ammonium acetate under suitable conditions. 4-Substituted-1(2H)- phthalazinone derivative (6), which undergoes N-alkylation using ethyl bromoacetate to produce the phthalazinone acetic acid ethyl ester derivative (7), that followed by the interaction with hydrazine monohydrate to afford the phthalazinone acetic acid hydrazide derivative (8). The latter product was conducted with different aromatic acid compounds in presence of POCl₃, to give the correlating oxadiazoles (9,10). The chemical structures of all the synthesized compounds are confirmed using physical and spectral data analyses like FT- IR, ¹H-NMR, and mass spectroscopy.