Scheme 2: Synthesis of phthalazinone derivatives 7-9. Reagents and conditions: (a) CHCl3, reflux, 5 h, 51%; (b) hydrazinehydrate, EtOH, addition at rt and then reflux, 90˚C, 2 h, 71%; (c) MeI, KOBut, DMF, 30 min, 80%; (d) LiOH, THF:MeOH:water (1:1:1), rt, 8–10 h, 81%.