Palladium-catalyzed C-H functionalization of pyridine-N-oxides: Highly selective alkenylation and direct arylation with unactivated arenes

TLDR: 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 and their corresponding ortho-alkenylated N-oxide derivatives are obtained in good to excellent yields.

Abstract: 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.