Reaction of Quinoline N-Oxides and Pyridine N-Oxides with Arylzinc Reagents: Synthesis of 2-Arylquinolines and 2-Arylpyridines

Graphical Reaction of quinoline N -oxides and pyridine N -oxides with arylzinc reagents under transition-metal-free conditions was studied. The reaction was carried out in toluene (for quinoline N -oxides) or THF (for pyridine N -oxides) at 100 °C and required 2 equiv. of arylzinc loadings and the presence of 2.5 equiv. of TFAA, affording 2-arylquinolines and 2-arylpyridines, respectively, in 24% to 95% yields. Reaction of quinoline N -oxides and pyridine N -oxides with arylzinc reagents under transition-metal-free conditions was studied. The reaction was carried out in toluene (for quinoline N -oxides) or THF (for pyridine N -oxides) at 100 °C and required 2 equiv. of arylzinc loadings and the presence of 2.5 equiv. of TFAA, affording 2-arylquinolines and 2-arylpyridines, respectively, in 24% to 95% yields. Functional groups OMe, F, Cl, Br, CF 3 , C(O)NH 2 , COOR and NO 2 were tolerated. Mechanistic studies showed that the reaction of quinoline N -oxides proceeded via a 2-arylquinolin-1(2 H )-olate intermediate, and the reaction of pyridine N -oxides via a 5-arylpenta-2,4-dienal oxime intermediate.