Transition metal-catalyzed C-H bond functionalization for the C-C bond formation has emerged as a promising area in organic synthesis. In particular, reactions involving Pd-catalyzed activation of sp2 or sp3 C-H bonds of arenes or alkanes have been extensively investigated. Successful applications of the similar activation strategy on readily available substrates have been also reported using various metals other than Pd catalysts.
In light of the importance of C-H bond transformation, we have developed two catalytic protocols of the oxidative C-C bond formation 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.