2-Amino-5,6-difluorophenyl-1-pyrazole-Directed Pd Catalysis: Arylation of Unactivated β-C(sp)-H Bonds.

Palladium-catalyzed arylation of unactivated β-C(sp)-H bonds in carboxylic acid derivatives with aryl iodides is described for the first time using 2-amino-5,6-difluorophenyl-1-pyrazole as an efficient and readily removable directing group. Two fluoro groups are installed at the 5- and 6-position of the anilino moiety in 2-aminophenyl-1-pyrazole, clearly enhancing the directing ability of the auxiliary. In addition, the protocol employs Cu(OAc)/AgPO (1.2/0.3) as additives, evidently reducing the stoichiometric amount of expensive silver salts. Furthermore, this process exhibits high β-site selectivity, compatibility with diverse substrates containing α-hydrogen atoms, and excellent functional group tolerance.