Fast and Efficient Nickel(II)‐catalysed Transfer Hydrogenation of Quinolines with Ammonia Borane

Abstract Herein we report the first Ni(II)‐catalysed transfer hydrogenation of quinolines using ammonia borane (AB) as hydrogen (H 2 ) source. An in situ generated Ni(II)‐bis(pyrazolyl)pyridine pre‐catalyst could hydrogenate quinoline and its derivatives in excellent yields of up to 90% at 25 °C in 30 minutes. Spectroscopic studies revealed that a Ni(II)‐hydride is responsible for the transfer hydrogenation of quinoline to 1,2,3,4‐tetrahydroquinoline via a 1,4‐dihydroquinoline intermediate. magnified image