Palladium-catalyzed alkenylation of quinoline-N-oxides via C-H activation under external-oxidant-free conditions.

The direct cross-coupling of quinoline-N-oxides with olefin derivatives has been realized using palladium acetate as the catalyst in the absence of external ligand and oxidant to give the corresponding 2-alkenylated quinolines and 1-alkenylated isoquinolines chemo- and regioselectively in 27-95% yield. The catalytic process is proposed to proceed via direct C-H bond activation of the quinoline-N-oxide with Pd(OAc)(2) followed by Heck coupling with the olefin. The resultant N-oxide of the alkenylated quinoline can oxidize the reduced Pd(0) to regenerate the Pd(II) active species and simultaneously release the 2-alkenylated quinoline without using any external oxidants and reductants.