[Synthesis]
General procedure for the synthesis of 5-bromophthalazine from the compound (CAS:1104070-89-4): to a 250 mL three-necked round-bottomed flask was added (1E,2E)-1,2-bis(3-bromobenzylidene)hydrazine (13.0 g, 35.5 mmol), aluminum(III) chloride (71.0 g, 533 mmol) and aluminum(III) bromide (71.0 g, 266 mmol). (71.0 g, 266 mmol). The reaction mixture was stirred at 185-200 °C for 1 hour. After completion of the reaction, the dark colloidal mass was cooled in an ice bath and 1.5 L of water was slowly added. The resulting suspension was filtered and the precipitate was washed with 5% hydrochloric acid solution. Subsequently, the filtrate was adjusted to alkaline with 15% potassium hydroxide solution and extracted three times with ethyl acetate (EtOAc). The organic phases were combined, dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residue was recrystallized by solvent mixture of ethyl acetate and hexane to give 5-bromophthalazine (3.12 g, 42% yield). The product was detected by LCMS and showed the (M + H)+ peak of 209.2, which was consistent with the calculated value of 209.0 for C8H6BrN2.1H NMR (400 MHz, CDCl3) data were as follows: δ 7.78-7.83 (m, 1H), 7.95 (d, J = 8.02 Hz, 1H), 8.14 (d, 1H), 9.49 (s, 2H). |