Solution to the C3-Arylation of Indazoles: Development of a Scalable Method.

3-(Hetero)arylindazoles are important motifs in several biologically active compounds. Mild and flexible palladium-mediated Negishi reaction conditions are reported for the introduction of (hetero)aryl moieties at the 3-position of N(2)-SEM-protected indazoles in high yields. The requisite Zn-species are readily obtained via regioselective deprotonation and subsequent transmetalation. The methodology tolerates a variety of functional groups on both coupling partners and has been extended to bis-haloarene and heteroarene coupling partners where the most reactive halogen reacts first, leaving the second halogen for subsequent functionalization.