Palladium-Catalyzed C−H Functionalization of Pyridine N-Oxides: Highly Selective Alkenylation and Direct Arylation with Unactivated Arenes

Two catalytic protocols of the oxidative C−C bond formation have been developed on the basis of the C−H bond activation of pyridine N-oxides. Pd-catalyzed alkenylation of the N-oxides proceeds with excellent regio-, stereo-, and chemoselectivity, and the corresponding ortho-alkenylated N-oxide derivatives are obtained in good to excellent yields. Direct cross-coupling reaction of pyridine N-oxides with unactivated arene was also developed in the presence of Pd catalyst and Ag oxidant, which affords ortho-arylated pyridine N-oxide products with high site-selectivity.