Copper(II)‐Mediated Regioselective <i>Ortho</i> ‐C−N Bond Formation on Phthalazinones Employing Sulfonamides

ABSTRACT A regioselective Cu(II)‐mediated phthalazinone‐directed C─N bond formation has been developed using sulfonamide as an efficient sulfonamidating partner. This method provides the desired products with excellent site selectivity, broad functional group tolerance, and consistently good yields. Its robustness is further demonstrated through successful gram‐scale synthesis. Moreover, the synthetic utility of this strategy was highlighted through downstream transformations, molecular docking studies, and ADME/T evaluations, underscoring its potential to access structurally diverse and biologically relevant N ‐heterocycles. Overall, this methodology offers a valuable platform for constructing phthalazinone derivatives with anticipated biological relevance.