Pd‐catalyzed N‐arylations of 3‐aryl‐1‐tosyl‐1H‐pyrazol‐5‐amines with arylbromides and the migration of Ts group

An efficient palladium-catalyzed N-arylations of 3-aryl-1-tosyl-1H-pyrazol-5-amines with arylbromides is established. A series of diversified N-arylated products are obtained in excellent yields with broad substrate scope. Importantly, the N-arylated products undergo 1,4- and 1,6-migration reactions of Ts group under the action of Cs2CO3, affording the N-Ts-substituted pyrroles as major products (1,6-migration). Similar results can also be directly obtained by palladium-catalyzed reactions of 3-aryl-1-tosyl-1H-pyrazol-5-amines with arylbromides in the presence of Cs2CO3 as a base. Mechanistic studies reveal that the Ts-migration is achieved through an intermolecular pathway.