A direct ortho‐Csp2‐H acylalkylation of 2‐aryl‐2,3‐dihydrophthalazine‐1,4‐diones with unsubstituted and substituted allyl alcohols is achieved in high yields through Rh(III)‐catalyzed C‐H bond activation process. The additional employment of Cu(OAc)2.2H2O as an oxidant detour the reaction towards [4+1] annulation, producing 13‐(2‐oxopropyl)‐13H‐indazolo[1,2‐b]phthalazine‐6,11‐diones in moderate yields. Interestingly, Lawesson’s reagent‐mediated conditions accomplished intramolecular cyclization in ortho‐(formylalkylated)‐2,3‐dihydrophthalazine‐1,4‐diones to produce diazepino[1,2‐b]phthalazine‐diones in moderate yields. Furthermore, allyl alcohol showcased distinct reactivity in presence of different additives to produce ortho‐allylated, oxidative and non‐oxidative [4+2] annulated products.