C2-Arylation of Substituted Pyridine N-oxides with Heteroaryl Carboxylic Acids by Palladium-Catalyzed Decarboxylative Coupling

A palladium catalyzed CH activation/ortho-arylation of heteroaryl-N-oxides through a decarboxylative coupling of heteroaryl carboxylic acids is described. Heterobiaryl-N-oxides, which are difficult to access by conventional methods, can be obtained in a single step. A wide range of functional groups, including metal-susceptible groups, such as bromo and iodo, can be tolerated under the reaction condition. The regioselectivity with respect to both carboxylic acid and N-oxide is excellent. Further, the N-oxides were used as a tool to examine the efficiency of decarboxylative coupling compared with aryl halide coupling.