Raney Nickel Catalyzed Highly Chemoselective Hydrogenation for Synthesis of Tetrahydroquinolines and Indolines in Water

The selective hydrogenation of privileged heterocycles with earth-abundant metal catalysts remains a significant yet practically important challenge in heterogeneous catalysis. Herein, we report a simple and efficient Raney nickel-catalyzed protocol for the selective hydrogenation of quinolines and indoles, delivering isolated yields of up to 99%. The practical utility of the method was further demonstrated through successful gram-scale transformations, and its use of a green solvent, an inexpensive catalyst, and operationally simple conditions affords a robust and sustainable approach for scalable heterocycle hydrogenation.