Regioselective zincation of indazoles using TMP2 Zn and Negishi cross-coupling with aryl and heteroaryl iodides

摘要

The metalation of various SEM-protected functionalized indazoles with TMP_2Zn provides 3-zincated indazoles which undergo palladium-catalyzed Negishi cross-couplings in good yields. Indazoles are an important class of N-heterocycles which have found numerous pharmaceutical applications. The direct lithiation or magnesiation of indazoles at position 3 is difficult due to a facile fragmentation of these heterocycles leading to aminonitriles (Scheme 1).