Catalytic Selective 1,2-Reduction of Quinolines by Dinuclear Rare Earth Metal Alkyl Complexes

The reactions of RE(CH₂SiMe₃)₃(THF)₂ with N,N-dimethylethyl-functionalized 5,6,7,8-tetrahydroquinolin-8-amino ligand 1 afforded a series of dinuclear rare earth metal alkyl complexes 2a-2d bearing a dianionic 5,6,7,8-tetrahydroquinolin-8-amido ligand through deprotonation and C-H bond activation processes. These dinuclear rare earth metal alkyl complexes efficiently catalyzed the selective 1,2-reduction of quinolines with ammonia borane (H₃N·BH₃) to give the corresponding 1,2-dihydroquinolines in high yields, which provided a mild and efficient approach for the synthesis of 1,2-dihydroquinolines with broad functional group compatibility.