Tandem reduction and trifluoroethylation of quinolines and quinoxalines with trifluoroacetic acid and trimethylamine borane.

A metal-free tandem reduction and N -trifluoroethylation of quinolines and quinoxalines has been developed. It provided a convenient route to access trifluoroethylated tetrahydroquinolines and tetrahydroquinoxalines. This one-pot method avoids the purification process of the intermediate. Mechanistically, the in situ -generated boryl acetal species reacted with tetrahydroquinolines to generate iminiums followed by reduction to give the target compounds.