Palladium‐Catalyzed Trifluoroethylation of Benzo[ h ]quinoline Derivatives by Mesityl(2,2,2‐trifluoroethyl)iodonium Triflate

Reactions of a dimeric [(bzq)Pd(OAc)] 2 complex ( 1 a′ ) and mesityl(2,2,2‐trifluoroethyl)iodonium triflate ( 2 a ) with or without additives at room temperature gave 10‐(2,2,2‐trifluoroethyl)benzo[ h ]quinoline rapidly in moderate to high yields. The reaction might proceed through a unstable binuclear “Pd III −CH 2 CF 3 ” intermediate ( I ), which was likely formed in situ from the oxidative addition of 2 a to [(bzq)Pd(OAc)] 2 and favorably transformed to mononuclear “(bzq)Pd IV −CH 2 CF 3 ” complexes ( III ) in the presence of another equiv.alent of 2 a and a suitable additive. Based on these, a Pd‐catalyzed C−H trifluoroethylation of benzo[ h ]quinolines with 2 a was developed. Numerous benzo[ h ]quinoline derivatives reacted with [MesICH 2 CF 3 ][OTf] at room temperature in the presence of 10 mol% Pd(OAc) 2 and 2 equiv.. NaHCO 3 to provide the corresponding 10‐trifluoroethylated products in excellent yields.