(2‐Pyridyl)sulfonyl Groups for ortho‐Directing Palladium‐ Catalyzed Carbon–Halogen Bond Formation at Functionalized Arenes

We describe an efficient palladium-catalyzed selective C–H ortho-monohalogenation (X = I, Br, Cl, F) of various functionalized N-(2-pyridyl)arylsulfones. Ortho-, meta- and para-functionalization is tolerated at the arene group which undergoes C–H halogenation. Some modifications are also possible on the 2-(arylsulfonyl)heteroaryl directing groups. A comparison of the halogenation efficiency suggests that bromination is the practical method of choice, while chlorination and fluorination are possible but more challenging. Under forcing conditions ortho-dihalogenation can also be achieved.